| d909f169 |
1 | CDECK ID>, INFORM. |
| 2 | |
| 3 | H E R W I G |
| 4 | |
| 5 | a Monte Carlo event generator for simulating |
| 6 | +---------------------------------------------------+ |
| 7 | | Hadron Emission Reactions With Interfering Gluons | |
| 8 | +---------------------------------------------------+ |
| 9 | G. Marchesini, Dipartimento di Fisica, Universita di Milano |
| 10 | I.G. Knowles(*), M.H. Seymour(+) and B.R. Webber, |
| 11 | Cavendish Laboratory, Cambridge |
| 12 | ------------------------------------------------------------------------ |
| 13 | with Deep Inelastic Scattering and Heavy Flavour Electroproduction by |
| 14 | G.Abbiendi(@) and L.Stanco, Dipartimento di Fisica, Universita di Padova |
| 15 | ------------------------------------------------------------------------ |
| 16 | and Jet Photoproduction in Lepton-Hadron Collisions |
| 17 | by J. Chyla, Institute of Physics, Prague |
| 18 | ------------------------------------------------------------------------ |
| 19 | (*)present address: Dept. of Physics & Astronomy, University of Glasgow |
| 20 | ------------------------------------------------------------------------ |
| 21 | (+)present address: Theory Division, CERN |
| 22 | ------------------------------------------------------------------------ |
| 23 | (@)present address: DESY, Hamburg |
| 24 | ------------------------------------------------------------------------ |
| 25 | Version 5.9 - 22nd July 1996 |
| 26 | ------------------------------------------------------------------------ |
| 27 | Main reference: |
| 28 | G.Marchesini, B.R.Webber, G.Abbiendi, I.G.Knowles, M.H.Seymour, |
| 29 | and L.Stanco, Computer Physics Communications 67 (1992) 465. |
| 30 | ------------------------------------------------------------------------ |
| 31 | Please send e-mail about this program to one of the authors at the |
| 32 | following addresses: |
| 33 | Decnet : 19616::webber, vxdesy::abbiendi, 19800::knowles |
| 34 | Internet : webber@hep.phy.cam.ac.uk, knowles@v2.ph.gla.ac.uk, |
| 35 | seymour@surya11.cern.ch, abbiendi@vxdesy.desy.de |
| 36 | ------------------------------------------------------------------------ |
| 37 | |
| 38 | ****** CONTENTS ****** |
| 39 | |
| 40 | 1. INTRODUCTION |
| 41 | 2. NEW FEATURES OF THIS VERSION |
| 42 | 3. FEATURES NOT YET INCLUDED |
| 43 | 4. PROGRAM STRUCTURE |
| 44 | 5. BEAMS AND PROCESSES |
| 45 | 6. INPUT PARAMETERS |
| 46 | 7. COMMON BLOCK FILE |
| 47 | 8. FORM FACTOR FILE |
| 48 | 9. EVENT DATA |
| 49 | 10. STATUS CODES |
| 50 | 11. EVENT WEIGHTS |
| 51 | 12. HEAVY FLAVOUR DECAYS |
| 52 | 13. SPACE-TIME STRUCTURE OF EVENTS |
| 53 | 14. COLOUR REARRANGEMENT MODEL |
| 54 | 15. QCD HARD SUBPROCESSES |
| 55 | 16. DIRECT PHOTON SUBPROCESSES |
| 56 | 17. QCD HIGGS PLUS JET SUBPROCESSES |
| 57 | 18. ELECTROWEAK SUBPROCESSES |
| 58 | 19. INCLUDING NEW SUBPROCESSES |
| 59 | 20. ERROR CONDITIONS |
| 60 | 21. SAMPLE OUTPUT |
| 61 | 22. GUIDE TO SAMPLE OUTPUT |
| 62 | |
| 63 | ------------------------------------------------------------------------ |
| 64 | |
| 65 | ****** 1. INTRODUCTION ****** |
| 66 | |
| 67 | HERWIG is a general-purpose event generator for high energy hadronic |
| 68 | processes, with particular emphasis on the detailed simulation of |
| 69 | QCD parton showers. The program has the following special features: |
| 70 | |
| 71 | * Simulation of any combination of hard lepton, hadron or photon |
| 72 | scattering and soft hadron-hadron collisions in one package. |
| 73 | |
| 74 | * Colour coherence of partons (initial and final) in hard subprocesses |
| 75 | |
| 76 | * Heavy flavour hadron production and decay with QCD coherence effects |
| 77 | |
| 78 | * QCD jet evolution with soft gluon interference via angular ordering |
| 79 | |
| 80 | * Backward evolution of initial-state partons including interference |
| 81 | |
| 82 | * Azimuthal correlations within and between jets due to interference |
| 83 | |
| 84 | * Azimuthal correlations within jets due to gluon polarization |
| 85 | |
| 86 | * Cluster hadronization of jets via non-perturbative gluon splitting |
| 87 | |
| 88 | * A complete space-time picture from parton showers to hadronic decays |
| 89 | |
| 90 | * A colour rearrangement model based on an events space-time structure |
| 91 | |
| 92 | * A similar cluster model for soft and underlying hadronic events |
| 93 | |
| 94 | Further details may be found in the references cited above and at the |
| 95 | end of this section, and in comments distributed throughout the code. |
| 96 | |
| 97 | The program operates by setting up parameters in common blocks and |
| 98 | then calling a sequence of subroutines to generate an event. Para- |
| 99 | meters not set in the main program HWIGPR are set to default values |
| 100 | in the main initialisation routine HWIGIN. |
| 101 | |
| 102 | To generate events the user must first set up the beam particle names |
| 103 | PART1, PART2 (type CHARACTER*8) in the common block /HWBEAM/, and the |
| 104 | beam momenta PBEAM1, PBEAM2 (in GeV/c), a process code IPROC and the |
| 105 | number of events required MAXEV in /HWPROC/. See section 5 for beams |
| 106 | and processes available. |
| 107 | |
| 108 | All analysis of generated events (histogramming, etc.) should be |
| 109 | performed by the user-provided routines HWABEG (to initialise), |
| 110 | HWANAL (to analyse an event) and HWAEND (to terminate). At present |
| 111 | HWANAL writes event information and stable particle data on unit |
| 112 | LWEVT defined in HWIGIN (or simply returns if LWEVT=0). See HWANAL |
| 113 | for details of event information written. Note that HWANAL should |
| 114 | always begin with the line |
| 115 | IF (IERROR.NE.0) RETURN |
| 116 | to prevent it being executed for incomplete events. |
| 117 | |
| 118 | A detailed event summary is printed out for the first MAXPR events |
| 119 | (default MAXPR=1). Set IPRINT=2 to list the particle identity codes |
| 120 | and (simplified) particle decay schemes used in the program. |
| 121 | |
| 122 | The programming language is standard Fortran 77 as far as possible. |
| 123 | However, the following may require modification for running on |
| 124 | computers other than Vax's: |
| 125 | |
| 126 | * Most common blocks are inserted by INCLUDE 'HERWIG59.INC' Vax |
| 127 | Fortran statements (see below for contents of HERWIG59.INC) |
| 128 | |
| 129 | * Subroutine HWUTIM (returning CPU time left) is machine dependent. |
| 130 | |
| 131 | The principal references are: |
| 132 | |
| 133 | G.Marchesini and B.R.Webber, Nucl. Phys. B310 (1988) 461; I.G. |
| 134 | Knowles, Nucl. Phys. B310 (1988) 571; S.Catani, G.Marchesini and |
| 135 | B.R.Webber, Nucl. Phys. B349 (1991) 635; G.Abbiendi and L.Stanco, |
| 136 | Comp.Phys.Comm. 66 (1991) 16, Zeit. Phys. C51 (1991) 81; |
| 137 | M.H.Seymour, Zeit. Phys. C56 (1992) 161. |
| 138 | |
| 139 | |
| 140 | Some additional relevant references are: |
| 141 | |
| 142 | A.Bassetto, M.Ciafaloni and G.Marchesini, Phys. Rep. 100 (1983) 201; |
| 143 | G. Marchesini and B.R. Webber, Nucl. Phys. B238 (1984) 1; Phys. |
| 144 | Rev. D38 (1988) 3419; B. R. Webber, Nucl. Phys. B238 (1984) 492; |
| 145 | Ann. Rev. Nucl. Part. Sci. 36 (1986) 253; I.G. Knowles, Nucl. Phys. |
| 146 | B304 (1988) 794; Computer Phys. Comm. 58 (1990) 271. |
| 147 | ------------------------------------------------------------------------ |
| 148 | |
| 149 | ****** 2. NEW FEATURES OF THIS VERSION ****** |
| 150 | |
| 151 | * The common block file HERWIG59.INC has been significantly rearranged |
| 152 | and tidied up. |
| 153 | |
| 154 | * Many new hadrons have been added. All S & P wave mesons are present |
| 155 | including the 1^P_0 & 3^P_1 states and many new, excited B^**, B_c & |
| 156 | quarkonium states. Also all D wave kaons and some `light' I=3 states |
| 157 | [pi_2, rho(1700) & rho_3]. All the baryons (singlet/octet/decuplet) |
| 158 | containing up to one heavy (c,b) quark are included. |
| 159 | |
| 160 | --- Consequently the default parameters require retuning --- |
| 161 | |
| 162 | * New 8-character particle names have been introduced and the revised |
| 163 | 7 digit PDG numbering scheme, as advocated in the LEP2 report, has |
| 164 | been adopted. |
| 165 | |
| 166 | * The layout of HWUDAT has been altered to make it easier to identify |
| 167 | and modify particle propeties. Three new arrays have been introduced |
| 168 | RLTIM, RSPIN & IFLAV. These are: the particle's lifetime (ps), spin, |
| 169 | and a code which specifies the flavour content of each hadron - used |
| 170 | (in HWURES) to create sets of iso-flavour hadrons for cluster decay. |
| 171 | Using the standard numbering of quark flavours the convention is: |
| 172 | |
| 173 | mesons: n_q n_qbar Eg. pi^+: 21, pi^-: 12 |
| 174 | baryons: +/-n_q1 n_q2 n_q3 Eg. Xi^0: 332, Xi^0bar: -332 etc. |
| 175 | (-ve for antibaryons; digits in decreasing order) |
| 176 | |
| 177 | Light, neutral mesons are identified as: 11 if I=1: pi^0,rho^0,... |
| 178 | 33 if I=0: eta, eta'.. etc. |
| 179 | |
| 180 | Some parts of the program have been automated so that it is possible |
| 181 | for the user to add new particles by specifying their properties via |
| 182 | the arrays in /HWPROP/ & /HWUNAM/ and increasing NRES appropriately: |
| 183 | this should be done before a call to HWUINC. |
| 184 | |
| 185 | As an example following lines add an isoscalar, spin pi state 'STAN' |
| 186 | and a (very light) stable toponium state 'BEER' with the decay mode: |
| 187 | STAN ---> BEER+BEER+BEER. |
| 188 | |
| 189 | NRES=NRES+1 |
| 190 | RNAME(NRES)='STAN ' |
| 191 | IDPDG(NRES)=666 |
| 192 | IFLAV(NRES)=11 |
| 193 | ICHRG(NRES)=0. |
| 194 | RMASS(NRES)=0.5 |
| 195 | RLTIM(NRES)=1.000D-10 |
| 196 | RSPIN(NRES)=3.142 |
| 197 | NRES=NRES+1 |
| 198 | RNAME(NRES)='BEER ' |
| 199 | IDPDG(NRES)=66 |
| 200 | IFLAV(NRES)=66 |
| 201 | ICHRG(NRES)=0. |
| 202 | RMASS(NRES)=0.1 |
| 203 | RLTIM(NRES)=1.000D+30 |
| 204 | RSPIN(NRES)=0.0 |
| 205 | CALL HWMODK(666,1.D0,0,66,66,66,0,0) |
| 206 | |
| 207 | |
| 208 | * The mixing angles of all the light, I=0 mesons can now be set using: |
| 209 | |
| 210 | ETAMIX: eta <-> eta' F0MIX: f_0(1300) <-> f_0(980) |
| 211 | PHIMIX: omega <-> phi, F1MIX: f_1(1285) <-> f_1(1510) |
| 212 | H1MIX: h_1(1170) <-> h_1(1380) F2MIX: f_2 <-> f_2' |
| 213 | |
| 214 | * Using the logical arrays VTOCDK & VTORDK the production of specified |
| 215 | particles can be stopped in both cluster decays and via the decay of |
| 216 | other unstable resonances. |
| 217 | |
| 218 | * A priori weights for the relative production rates in cluster decays |
| 219 | of mesons and baryons differing only via their S & L quantum numbers |
| 220 | can be supplied using SNGWT & DECWT for singlet (i.e. Lambda-like) & |
| 221 | decuplet baryons and REPWT for mesons. The old VECWT now corresponds |
| 222 | to REPWT(0,1,0) and TENWT to REPWT(0,2,0). |
| 223 | |
| 224 | * The default masses of the c and b quarks have been lowered to 1.55 & |
| 225 | 4.95 repectively: this corresponds to the mass of the lightest meson |
| 226 | minus the u/d quark mass. This increases the number of heavy mesons, |
| 227 | and hence total multiplicities, and slightly softens their momentum |
| 228 | spectrum. The rate of photoproduced charm states increases and B-pi |
| 229 | momentum correlations become smoother. |
| 230 | |
| 231 | * The resonance decay tables supplied in the program have been largely |
| 232 | revised. Measured/expected modes with branching fraction at or above |
| 233 | 1 per mille are given, including 4 & 5 body decays. To print the new |
| 234 | tables call HWUDPR. |
| 235 | |
| 236 | * The arrays FBTM, FTOP & FHVY which stored the branching fractions of |
| 237 | the bottom, top & heavier quarks' `partonic' decays are now nolonger |
| 238 | used. Such decays are specified in the same way as all other decay |
| 239 | modes: this permits different decays to be given to individual heavy |
| 240 | hadrons. Partonic decays of charm hadrons and quarkonium states are |
| 241 | also now supported. The products' order in a partonic decay mode is |
| 242 | significant. For example if the decay is: Q --> W+q --> (f+fbar')+q, |
| 243 | occuring inside a Q-sbar hadron the required ordering is: |
| 244 | |
| 245 | Q+sbar --->(f+fbar')+(q+sbar) |
| 246 | or (q+fbar')+(f+sbar) `colour rearranged' |
| 247 | |
| 248 | In both cases the (V-A)^2 ME^2 is proportional to: p_0.p_2 * p_1*p_3 |
| 249 | |
| 250 | * The structure of the program has been altered so that secondary hard |
| 251 | subrocess and subsequent fragmentation associated with each partonic |
| 252 | heavy hadron decay appear separately. Thus pre-hadronization t quark |
| 253 | decays are treated individually as are any subsequent bottom hadron |
| 254 | partonic decays. |
| 255 | |
| 256 | * Additionally decays of heavy hadrons to exclusive non-partonic final |
| 257 | states are supported. No check against double counting from partonic |
| 258 | modes is included. However this isn't expected to be a major problem |
| 259 | for the semi-leptonic and 2-body hadronic modes supplied. |
| 260 | |
| 261 | * An array NME has been introduced to enable a possible matrix element |
| 262 | to be specified for each decay mode. |
| 263 | |
| 264 | NME = 0 Isotropic decay |
| 265 | 100 Free particle (V-A)*(V-A): p_0.p_2 * p_1.p_3 |
| 266 | 101 Bound quark (V-A)*(V-A): p_0.p_2 * p_1*[p_3 - xs*p_0] |
| 267 | xs = m_Q/M_0 - spectator quark momentum fraction |
| 268 | 130 Ore & Powell ortho-positronium ME^2: onium --> gg+g/gamma. |
| 269 | |
| 270 | The list of matrix elements presently supported is modest, users are |
| 271 | urged to contact an author to have other MEs implimentated. |
| 272 | |
| 273 | * The decay tables can be written to/read from a file by using HWIODK, |
| 274 | adopting the format advocated in the LEP2 report. In addition to the |
| 275 | PDG numbering of particles the HERWIG numbers or character names can |
| 276 | be used. This permits easy alteration of the decay tables. In HWUINC |
| 277 | a call is made to HWUDKS which sets up HERWIGs internal pointers and |
| 278 | performs some basic checks of the decay tables. Each decay mode must |
| 279 | conserve charge and be kinematically allowed and not contain vetoed |
| 280 | decay products. The sum of a particles branching ratios is set to 1. |
| 281 | Also a warning is printed if an antiparticle does not have all the |
| 282 | charge conjugate decays modes of the particle. |
| 283 | |
| 284 | * HWMODK enables changes to the decay tables to be made by alterating/ |
| 285 | adding single decay modes including on an event by event basis. This |
| 286 | can be done before HWUINC, in which case when altering the BR and/or |
| 287 | ME code of an existing mode a warning is given of a duplicate second |
| 288 | mode which supercedes the first. BRs set below 10^-6 are eliminated, |
| 289 | whilst if one mode is within 10^-6 of 1 all other modes are removed. |
| 290 | Note that some forethought is required if the BRs of 2 modes of the |
| 291 | same particle are changed since the operation of rescaling to 1 the |
| 292 | BR sum causes a non-commutativity in the order of the calls. |
| 293 | |
| 294 | * Production vertex information is now made available, using VHEP, for |
| 295 | all partons, clusters and final state particles: set PRVTX=.TRUE. to |
| 296 | print them. The vertices of partons and clusters are given wrt local |
| 297 | coordinates associated with their individual hard sub-process. |
| 298 | |
| 299 | * All partonic and resonace rest frame lifetimes are generated with an |
| 300 | exponential distribution: exp(-t/<tau>)/<tau>. The average lifetime, |
| 301 | <tau>, is given in terms of the particles mass, width and virtuality |
| 302 | by: |
| 303 | hbar.sqrt(q^2) |
| 304 | <tau>(q^2) = ----------------------------- |
| 305 | \/(q^2-M^2)^2 + (Gamma.q^2/M)^2 |
| 306 | |
| 307 | = hbar/Gamma for an on-shell particle |
| 308 | ~ hbar.q/(q^2-M^2) a highly virtual particle |
| 309 | |
| 310 | For partons an effective width = sqrt(VMIN2), to act as a cut-off on |
| 311 | lifetimes, is introduced. |
| 312 | |
| 313 | * The space-time picture for cluster formation and splitting is partly |
| 314 | ad hoc and partly string inspired - no physics depends upon it. |
| 315 | |
| 316 | * All particles with lifetimes greater than PLTCUT are set stable. |
| 317 | |
| 318 | * If PIPSMR=.TRUE. the primary interaction point's spatial position is |
| 319 | is smeared according to the triple Gaussian in HWRPIP: this position |
| 320 | is assigned to the CMF track. |
| 321 | |
| 322 | * If MAXDKL=.TRUE. then each putative decay is tested in HWDXLM to see |
| 323 | that it occurs within a specified volume (cylinder/sphere for IOPDKL |
| 324 | =1/2): if not it is set stable. |
| 325 | |
| 326 | * If MIXING=.TRUE. then B^0_d,s mesons are allowed to oscillate: XMIX |
| 327 | and YMIX contain Delta-M/Gamma and Delta-gamma/2*Gamma respectively. |
| 328 | A new particle, ISTHEP=200, is introduced giving the flavour of the |
| 329 | neutral B meson at production in addition to the `decaying' track. |
| 330 | |
| 331 | * A multiple intra & inter-jet colour rearrangement model is available |
| 332 | for CLRECO=.TRUE. The q-qbar pairings in two non-adjacent clusters |
| 333 | are interchanged with probability PRECO if the distances between the |
| 334 | production vertices of both q-qbar pairs when added in quadrature is |
| 335 | reduced. EXAG can be used to artificially scale the lifetimes of any |
| 336 | weak bosons. |
| 337 | |
| 338 | * A number of bugs have been corrected: in HWEPRO for weighted events; |
| 339 | in HWSBRN affecting the reconstruction of the photon beam remnant; |
| 340 | and in HWHEPG stopping event generation. Plus minor modifications to |
| 341 | HWBGEN; in the use of HWHIGM by HWHIGJ; and small changes in HWHDIS |
| 342 | & HWHEGG. |
| 343 | |
| 344 | * A significant bug in HWDHQK, affecting top quark decays, was present |
| 345 | in version 5.8 ONLY. The scale of the top decay had been set to the |
| 346 | b-quark mass, stopping gluon radiation from the b and restricting |
| 347 | that from the W decay products to have transverse momentum less than |
| 348 | the b mass. The scales are now correctly set for top decays. |
| 349 | |
| 350 | * Improved efficiency of photon generation in HWEGAM. |
| 351 | |
| 352 | * New hard sub-process have been added: |
| 353 | |
| 354 | - Compton scattering, gamma + q --> gamma + q, IPROC=5300. |
| 355 | |
| 356 | - Two-to-two parton scattering via exchange of a colour singlet |
| 357 | IPROC=2400 Mueller-Tang pomeron: the fixed alpha_s and omega_0 are |
| 358 | given by ASFIXD and OMEGA0 respectively. |
| 359 | IPROC=2450 photon exchange, for like flavour qqbar pairs including |
| 360 | the t-channel component of the interference with q-qbar -> q-qbar. |
| 361 | |
| 362 | - Drell-Yan has been extended to the production of all fermion pairs |
| 363 | IPROC=1399; 1300 gives all quark flavours 1300+IQ a specific quark |
| 364 | flavour, 1350 all leptons (including neutrinos) 1350+IL a specific |
| 365 | lepton flavour. The s-channel component of the interference with |
| 366 | like flavour q-qbar scattering is included here. |
| 367 | |
| 368 | - Z+jet production is included as IPROC=2150 (HWHW1J becomes HWHV1J) |
| 369 | |
| 370 | * Running coupling now used for prompt J/PSI production in DIS. |
| 371 | |
| 372 | * The phase-space limits for the momentum fraction of incoming photons |
| 373 | in the Weizsacker-Williams approximation is now set by the variables |
| 374 | YWWMIN & YWWMAX, allowing different ranges for the tagged and |
| 375 | untagged photons in two-photon DIS. |
| 376 | |
| 377 | * Interfaced to the Schuler-Sjostrand parton distribution functions, |
| 378 | version 2. These appear as PDFLIB sets with author group 'SaSph', |
| 379 | but are actually implemented via a call to their SASGAM code. The |
| 380 | value in MODPDF specifices the set (1-4 for 1D [recommended set],1M, |
| 381 | 2D,2M), whether the Bethe-Heitler process is used for heavy flavours |
| 382 | (add 10), whether the P^2-dependence is included (add 20), and which |
| 383 | of their P^2 models is used (add 100 times their IP2 parameter). |
| 384 | |
| 385 | * New variables ANOMSC(1 or 2,IBEAM) record the evolution scale and Pt |
| 386 | at which an anomalous (gamma* --> q+qbar) splitting was generated in |
| 387 | the backward evolution of beam IBEAM. set 0 if no such splitting was |
| 388 | generated. This is implemented in HWBGEN and HWSBRN. |
| 389 | |
| 390 | * In preparation for multiple interactions, several routines have been |
| 391 | added or modified. New are: HWHREM for identifying and cleaning up |
| 392 | the beam remnants; HWHSCT to administer the extra scatters. Minor |
| 393 | modifications to: HWBGEN & HWSBRN, don't report energy conservation |
| 394 | errors when ISLENT = -1; HWSSPC, improved approximation for remnant |
| 395 | mass at high energies; and HWUPCM, improved safety against negative |
| 396 | square roots. |
| 397 | |
| 398 | * Photon Initial State Radiation in e+e- annihilation events allowed. |
| 399 | TMNISR sets the minimum s-hat/s value, ZMXISR sets the (arbitrary) |
| 400 | separation between unresolved and resolved emission; using ZMXISR=0 |
| 401 | switches off photon ISR. |
| 402 | |
| 403 | * Numerical integral in HWBDED now done analytically removing the need |
| 404 | to reintegrate for each new energy; in principle allowing use in 5- |
| 405 | jet WW events, but this is not yet implemented. |
| 406 | |
| 407 | * New phase-space variable WHMIN added. This sets the minimum allowed |
| 408 | hadronic mass and affects photoproduction reactions (gamma-hadron & |
| 409 | gamma-gamma) and DIS. In lepton-hadron DIS it is largely irrelevant |
| 410 | since there is already a cut on Bjorken y which at fixed s is almost |
| 411 | the same but for lepton-gamma DIS it makes a big difference. |
| 412 | |
| 413 | * A new treatment of running Higgs width and non-resonant diagrams, as |
| 414 | suggested in M.H. Seymour, Phys. Lett. B354 (1995) 409. Selected by |
| 415 | setting IOPHIG=2 or 3 (default); previous options 2 and 3 have been |
| 416 | withdrawn. Note that including the non-resonant diagrams changes the |
| 417 | meaning of what is generated: IOPHIG = 0 or 1, gives the s-channel |
| 418 | diagram, an unphysical choice of part of the amplitude; IOPHIG = 2 |
| 419 | or 3, gives the I=0 & J=0 part of the excess over the cross section |
| 420 | expected for a zero mass Higgs boson, a physical choice of part of |
| 421 | the cross section. The inclusion of non-resonant diagrams causes the |
| 422 | cross section to increase below and decrease above resonance. |
| 423 | |
| 424 | * New treatment of the splitting in two of clusters containing hadron |
| 425 | (or photon) remnants. Previous versions gave the 2 fragments a mass |
| 426 | spectrum typical of soft processes: dn/dm**2 = Gaussian. In the new |
| 427 | version the child containing the remnant is treated as before but |
| 428 | the other cluster, containing a perturbative parton, is treated as a |
| 429 | normal clusters: dn/dm = m**psplt. IOPREM controls this behaviour: 0 |
| 430 | = old version, 1 = new (default). |
| 431 | |
| 432 | * Direct gamma+gamma* -> q+qbar is included in the hard correction for |
| 433 | lepton-gamma DIS; plus minor bug fixed in HWBDIS. |
| 434 | |
| 435 | * The dummy routine IUCOMP has been removed, this avoids errors when |
| 436 | the program is linked to CERNLIB. |
| 437 | |
| 438 | * It has been noticed that differences in the way quark masses are |
| 439 | treated in different processes can cause inconsistencies between |
| 440 | different ways of generating the same process. The most noticeable |
| 441 | example is in direct photoproduction, where one can use process 9130 |
| 442 | or 5000. See the note at the end of Section 5 of the documentation |
| 443 | for more information on the strategies used in different processes. |
| 444 | |
| 445 | Version 5.1 of HERWIG was described in detail in Computer Physics |
| 446 | Communications 67 (1992) 465. For completeness we list here also the |
| 447 | main new features added in versions 5.2 - 5.7. |
| 448 | |
| 449 | In version 5.2: |
| 450 | |
| 451 | * New e+e- processes: |
| 452 | - two photon processes, IPROC = 500+ID where ID=0-10 is the same as |
| 453 | in Higgs processes for qqbar, llbar, and W+W-. The phase space is |
| 454 | controlled by EMMIN,EMMAX for the CMF mass, PTMIN,PTMAX for the |
| 455 | transverse momentum of the CMF in the lab, and CTMAX for the CMF |
| 456 | angle of the outgoing particles. |
| 457 | - photon-W fusion, IPROC = 550+ID where ID=0-9 is the same as in |
| 458 | Higgs processes, except that ID=1 or 2 both give the sum of dubar |
| 459 | and udbar etc. The phase space is controlled by EMMIN,EMMAX only. |
| 460 | The full 2-->3 matrix elements for photon e-->f f'bar nu are used, |
| 461 | so the cross section for real W production is correctly included. |
| 462 | - ZZ pair production, IPROC=250 is treated just like WW production, |
| 463 | and is based on the program kindly supplied by Zoltan Kunszt. |
| 464 | |
| 465 | * New ep processes: |
| 466 | - the phase space for BGF is now controlled by EMMIN,EMMAX as above. |
| 467 | The default values are 0 and RootS respectively, corresponding to |
| 468 | the behaviour of version 5.1 |
| 469 | - J/psi production from BGF, IPROC = 9104 is now available. |
| 470 | - W W fusion to Higgs is now available in ep, IPROC = 9500+ID. |
| 471 | |
| 472 | * IPROC = 1600+ID now gives the sum of gluon fusion and q qbar fusion. |
| 473 | This is especially important in e+e- if tan(beta) is large, when it |
| 474 | is dominated by e+e- --> e+e- gamma gamma --> e+e- b bbar H. |
| 475 | |
| 476 | * Users can now force Z --> b bbar decays, with MODBOS(i)=7 (for a |
| 477 | complete list see section 18). For example, IPROC=250, MODBOS(1)=7, |
| 478 | MODBOS(2)=0 gives ZZ production with one Z decaying to b bbar. |
| 479 | |
| 480 | * All Higgs vertices now include an enhancement factor to account for |
| 481 | non-SM couplings. ENHANC(ID), where ID=1-11 is the same as for Higgs |
| 482 | production, holds the ratio of the AMPLITUDE for the given vertex to |
| 483 | that of the SM. This of course only simulates the chargeless scalars |
| 484 | of any extended model, and not the pseudoscalars or charged Higgses. |
| 485 | |
| 486 | * The heavy quark content of the photon now uses the corrections to |
| 487 | the Drees-Grassie distribution functions for light quarks, recently |
| 488 | calculated by C.S.Kim et al. (see M.Drees & C.S.Kim, DESY 91-039 and |
| 489 | C.S.Kim, Durham preprint DTP/91/16). |
| 490 | |
| 491 | * A new structure function set, Owens1.1, similar to Duke+Owens1, but |
| 492 | fitted to new data (Preprint FSU-HEP-910606) is available via |
| 493 | NSTRU=5, and is now the default structure function set. |
| 494 | |
| 495 | In version 5.3: |
| 496 | |
| 497 | * O(alpha-s) jet production in ep processes has been included (IPROC= |
| 498 | 9200 etc), with Q**2 range controlled by Q2MIN, Q2MAX and minimum |
| 499 | jet transverse momentum (in the hard subprocess c.m. frame) set by |
| 500 | PTMIN. The new subroutines were written by Sebastian Brandis and we |
| 501 | are grateful to him for permission to use his code. |
| 502 | |
| 503 | * Minor bugs have been fixed in the backward evolution of quarks into |
| 504 | photons, hadronic processes in e+e-, remnant hadronization in ep, |
| 505 | and in the generation of weighted events (ie. with NOWGT=.FALSE.). |
| 506 | |
| 507 | In version 5.4: |
| 508 | |
| 509 | * A correction to hard gluon emission in e+e- events has been added |
| 510 | and is now the default process. This uses the O(alpha-s) matrix |
| 511 | element to add events in the `back-to-back' region of phase-space |
| 512 | corresponding to a quark-antiquark pair recoiling from a very hard |
| 513 | gluon. Although this is asymptotically negligible, and cannot be |
| 514 | produced within the shower itself, it has a sizeable effect at LEP |
| 515 | energies. As a result, the default parameters have been retuned, |
| 516 | and show a marked improvement in agreement with OPAL data for event |
| 517 | shapes sensitive to three-jet configurations (J.W. Gary, private |
| 518 | communication). The uncorrected process has been retained for |
| 519 | comparative purposes and is available as IPROC=120+IQ. |
| 520 | |
| 521 | * Photons are now included in time-like parton showering. The infra- |
| 522 | red cutoff is VPCUT, which defaults to SQRT(S) corresponding to no |
| 523 | emission. Agreement with LEP data is satisfactory if used together |
| 524 | with the matrix element correction to produce photons in the back- |
| 525 | to-back region. The results are insensitive to VPCUT variations |
| 526 | in the range 0.1-1.0 GeV. |
| 527 | |
| 528 | * W decay correlations and width are now correctly included in W+jet |
| 529 | production (previous versions used unpolarized, on-shell approx.). |
| 530 | |
| 531 | * An inconsistency in the argument used for alpha_s in the branching |
| 532 | g -> q qbar has been removed. The change is a non-leading correction |
| 533 | but leads to slightly more quarks in gluon jets. |
| 534 | |
| 535 | * A new parameter B1LIM has been introduced for B cluster hadroniz- |
| 536 | ation. If MCL is the B cluster mass and MTH the threshold for its |
| 537 | decay into 2 hadrons, the probability of its decay into a single B |
| 538 | hadron is: 1 if MCL<MTH, 0 if MCL>(1+B1LIM)*MTH, with a linear |
| 539 | interpolation i.e. 1-(MCL-MTH)/(B1LIM*MTH) if MTH<MCL<(1+B1LIM)*MTH. |
| 540 | Thus the default value B1LIM=0 gives the same as previous versions, |
| 541 | while B1LIM>0 gives a harder B spectrum. |
| 542 | |
| 543 | * B decays can now be performed by the EURODEC or CLEO Monte Carlo |
| 544 | packages. The new variable BDECAY controls which package is used: |
| 545 | 'HERW' for HERWIG; 'EURO' for EURODEC; 'CLEO' for CLEO. The EURODEC |
| 546 | package can be obtained from the CERN library. The CLEO package is |
| 547 | available by kind permission of the CLEO collaboration, and can be |
| 548 | obtained from Luca Stanco at the address given above. |
| 549 | |
| 550 | In version 5.5: |
| 551 | |
| 552 | * The Sudakov form factors can now be calculated using the one-loop or |
| 553 | two-loop alpha_s, according to the variable SUDORD (DEFAULT=1). The |
| 554 | parton showering still incorporates the two-loop alpha_s in either |
| 555 | case but if SUDORD=1 this is done using the veto algorithm, whereas |
| 556 | if SUDORD=2 no vetoes are used in the final-state evolution. This |
| 557 | means that the relative weight of any shower configuration can be |
| 558 | calculated in a closed form, and hence that showers can be `forced'. |
| 559 | For example, a package of routines should be available soon for |
| 560 | forcing jets to contain photons, which will therefore drastically |
| 561 | improve the efficiency of photon FSR studies. |
| 562 | To next-to-leading order the two possibilities SUDORD=1 or 2 should |
| 563 | be identical, but they differ at beyond-NLO, so some results may |
| 564 | change a little. Previous versions were equivalent to SUDORD=1. |
| 565 | |
| 566 | * Alpha_em is now multiplied by the factor ALPFAC (DEFAULT=1) for all |
| 567 | quark-photon vertices in jets, and in the `dead zone' in e+e-. This |
| 568 | is a cheap way of improving the efficiency of photon FSR studies, |
| 569 | which should not be needed once photon forcing is available. Note |
| 570 | that results at small ycut become sensitive to ALPFAC above about 5. |
| 571 | |
| 572 | * A new parameter CLPOW (DEFAULT=2) is available in the cluster hadro- |
| 573 | nization model. A cluster of mass MCL made of quarks of mass M1,M2 |
| 574 | is split into lighter clusters before decaying if |
| 575 | MCL**CLPOW > CLMAX**CLPOW + (M1+M2)**CLPOW |
| 576 | Thus the previous value was CLPOW=2, like the new default. Smaller |
| 577 | values will increase the yield of heavier clusters (and hence of |
| 578 | baryons) for heavy quarks, without affecting light quarks much. For |
| 579 | example, the default value gives no b-baryons (for the default value |
| 580 | of CLMAX) whereas CLPOW=1.0 makes b-baryons/b-hadrons about 1/4. |
| 581 | |
| 582 | * The event record has been modified to retain entries for all partons |
| 583 | before hadronization (with status ISTHEP=2). During hadronization, |
| 584 | the gluons are split into quark-antiquark, while other partons are |
| 585 | copied to a location (indicated by JDAHEP(1,*)) where their momenta |
| 586 | may be shifted slightly, to conserve momentum, during heavy cluster |
| 587 | splitting. Previously the original momenta were shifted, so momentum |
| 588 | appeared not to be conserved at the parton level. |
| 589 | |
| 590 | * Minor improvements have been made to: NLO correction to Higgs decays |
| 591 | to qqbar; pt spectra of outgoing electrons in two-photon processes; |
| 592 | quark-mass effects in gamma-W fusion; WW spectrum below threshold in |
| 593 | e+e-; t-bbar spectrum in W Drell-Yan (IPROC=1406). |
| 594 | |
| 595 | * Bugs preventing the use of Sudakov form factor tables from disk and |
| 596 | gluon-> diquarks splitting option under some circumstances, together |
| 597 | with other minor bugs and machine-dependences, have been fixed. |
| 598 | |
| 599 | In version 5.6: |
| 600 | |
| 601 | * Decays of very heavy quarks (top and higher generations) can occur |
| 602 | either before or after hadronization. At present all top quarks will |
| 603 | decay before/after hadronizing if the top mass is greater/less than |
| 604 | 130 GeV. This can be changed in subroutine HWDTOP. All higher (>3) |
| 605 | generations now decay before hadronization. Note that the new state- |
| 606 | ment CALL HWDHQK must appear in the main program between the calls |
| 607 | to HWBGEN and HWCFOR to carry out any decays before hadronization. |
| 608 | |
| 609 | * Bugs in the subroutine HWHDOA for O(alpha_s) jet production in DIS |
| 610 | have been corrected by J. Chyla, who has also extended this process |
| 611 | into the photoproduction region. If Q2MIN.LT.2D-6 (the new default), |
| 612 | the kinematic lower limit on Q**2 is computed and used. New options |
| 613 | IPROC=9250 to 9277 use various approximations to the neutral-current |
| 614 | matrix element, as specified in the Table below. |
| 615 | |
| 616 | * The photoproduction processes have also been extended from the |
| 617 | original heavy quark production program, to include all quark pair |
| 618 | production (IPROC=9100-9106) and QCD Compton (IPROC=9110-9122), as |
| 619 | well as the sum of the two (IPROC=9130). The possible flavours for |
| 620 | the 9100,9110 and 9130 processes are limited by the input parameters |
| 621 | IFLMIN and IFLMAX (defaults are 1 and 3, i.e. only u,d,s flavours). |
| 622 | The corresponding Charged Current processes are now provided via the |
| 623 | IPROC=9140-9144 codes. |
| 624 | |
| 625 | * All the DIS processes IPROC=9000-9599 are now available in e+e- as |
| 626 | well as lepton-hadron collisions. The program generates a photon |
| 627 | from the second beam (only) in Weizsacker-Williams approximation and |
| 628 | uses Drees-Grassie structure functions for DIS on the photon. |
| 629 | |
| 630 | * Pointlike photon-hadron scattering to produce QCD jets is available |
| 631 | as IPROC=5000. This is suitable for fixed-target photoproduction, |
| 632 | provided events are generated in a frame in which the target has |
| 633 | high momentum, and then boosted back to the lab. IPROC=5000+IQ gen- |
| 634 | erates only those processes involving quark flavour IQ, using exact |
| 635 | kinematics and light-cone momentum fraction. In both cases, after |
| 636 | event generation the hard subprocess code IHPRO is set to 51,52 or |
| 637 | 53 for photon+q->g+q, photon+qbar->g+qbar, or photon+g->q+qbar. |
| 638 | |
| 639 | * The default limits on Q**2 in DIS processes (Q2MIN,Q2MAX) have been |
| 640 | set very small/large (0.0, 1.D10) and are reset to the kinematic |
| 641 | limits unless changed by the user. This means the default Q2MIN is |
| 642 | not suitable for simple NC DIS (IPROC=9000 etc), but is appropriate |
| 643 | for jet and heavy quark photoproduction. |
| 644 | |
| 645 | * A new parameter NMXJET, the maximum number of outgoing partons in |
| 646 | a hard subprocess (default 200) has been introduced in the common |
| 647 | block file HERWIG56.INC. |
| 648 | |
| 649 | * For technical reasons, some HERWIG status codes ISTHEP between 153 |
| 650 | and 165 have changed their meanings. See the Table in sect.10 below. |
| 651 | |
| 652 | * Bugs in the hadronization of diquark-antidiquark clusters have been |
| 653 | fixed. Any such clusters with masses below threshold for decay into |
| 654 | baryon-antibaryon are shifted to the threshold via a transfer of 4- |
| 655 | momentum to a neighbouring cluster. |
| 656 | |
| 657 | * A bug in the default pion structure function (no gluons) is fixed. |
| 658 | |
| 659 | In version 5.7: |
| 660 | |
| 661 | - ELECTRO-WEAK COUPLINGS: New arrays QFCH(16), VFCH(16,2), AFCH(16,2) |
| 662 | and VCKM(3,3) have been set up for couplings and CKM matrix. See the |
| 663 | documentation file or HWIGIN for conventions. Note that universality |
| 664 | is not assumed, so lepton axial couplings may differ for example; this |
| 665 | is primarily to cover Z' possibilities, see below. The variable |
| 666 | SCABI=sin^2 theta_Cabibbo is however also retained for the present. |
| 667 | |
| 668 | - A Z' has been introduced with PDG code 32, HERWIG identifier 202, |
| 669 | default mass 500 GeV, width GAMZP (default 5 GeV) and name 'Z0PR'. |
| 670 | It is invoked by setting ZPRIME=.TRUE. (default .FALSE.). |
| 671 | |
| 672 | - POLARISATION: incoming lepton and antilepton beam polarisations |
| 673 | are now specified by setting two new vectors EPOLN(3) and PPOLN(3): |
| 674 | component 3 is longitudinal and 1,2 transverse. Transverse only occurs |
| 675 | in e+e- routines; recall that two transverse 'measurements' are needed |
| 676 | to see an effect so it should not arise elsewhere. Note that in DIS |
| 677 | processes you have to set either EPOLN if it is a lepton or (exclusive) |
| 678 | PPOLN if an antilepton. |
| 679 | |
| 680 | Polarisation effects are now included in e+e- 2/3 jet production |
| 681 | and Bjorken process, together with DIS processes apart from J/psi |
| 682 | production. |
| 683 | |
| 684 | - NEW SUBPROCESSES: |
| 685 | 2200 QCD direct photon pair production (inc. g+g->gamma+gamma) |
| 686 | 5100+IQ Point-like photon/QCD heavy flavour pair production |
| 687 | 5200+IQ Point-like photon/QCD heavy flavour single excitation |
| 688 | The latter two replace 5000+IQ, while 5000 remains as before (ie |
| 689 | a sum over all processes and flavours with simplified kinematics) |
| 690 | |
| 691 | - The kinematic reconstruction of DIS processes can now take place in |
| 692 | the Breit frame, if BREIT=.TRUE. (the default value). Previous versions |
| 693 | used the lab frame. Although the reconstruction is fully invariant under |
| 694 | Lorentz boosts along the incoming hadron's direction, it is not under |
| 695 | transverse boosts, so there should be some difference between the two |
| 696 | frames. The boost is not performed for very small Q^2 (<10^-4) to avoid |
| 697 | numerical instabilities, but the two frames are in any case equivalent |
| 698 | for such small Q^2. |
| 699 | |
| 700 | - A new parameter PRSOF to produce an underlying event in only a fraction |
| 701 | PRSOF of events (default=1.0). IPROC=19000 etc are thus equivalent to |
| 702 | PRSOF=0. |
| 703 | |
| 704 | - Non-diffractive hadronic minimum bias events (IPROC=8000) can now be |
| 705 | generated for a wider variety of beams (P,PBAR,PI+/-,K+/-,E+/-,MU+/-,GAMA |
| 706 | on target P; also P and PBAR or leptons on target N). The event weight |
| 707 | (previously set to 1.0 for this process) is the estimated cross section |
| 708 | based on the parametrizations of Donnachie and Landshoff, CERN-TH.6635/92. |
| 709 | The non-diffractive cross section is assumed to be 70% of the total. |
| 710 | For lepton beams a photon is first generated using the effective photon |
| 711 | approximation (see below) and then the on-shell photon cross section |
| 712 | is used. |
| 713 | |
| 714 | - A bug has been fixed in HWBRAN and HWSBRN (present in versions 5.1 to |
| 715 | 5.6) that led to too much transverse momentum being developed by the |
| 716 | parton showers in hadron-hadron collisions. All radiation with pt |
| 717 | greater than the hard process scale is now vetoed. In the case of |
| 718 | initial-state radiation, this affects all events, while for final-state |
| 719 | radiation it only affects those in which the two jets have a rapidity |
| 720 | difference of more than about 3.4. |
| 721 | |
| 722 | - When SUDORD=2, no veto is needed for gluon splitting to quarks. This |
| 723 | means that no vetoes are needed for final state showering, except for |
| 724 | the previously-mentioned transverse momentum cut. The removal of |
| 725 | vetoes allows preselection of the flavours that a jet will contain, |
| 726 | giving a huge increase in the efficiency of rare process simulation. A |
| 727 | package is already available to simulate heavy flavour production |
| 728 | inside jets, and the equivalent for photons should soon be available. |
| 729 | |
| 730 | - Parameter BTCLM is now available to users to adjust the mass parameter |
| 731 | in remnant formation. Its default value, 1.0, is identical to previous |
| 732 | versions. |
| 733 | |
| 734 | - There is a new switch CLDIR for cluster decays. CLDIR=0 is the same as |
| 735 | previous versions, while CLDIR=1 (the default) means that a cluster that |
| 736 | contains a `perturbative' quark, ie one coming from the perturbative |
| 737 | stage of the event (the hard process or perturbative gluon splitting) |
| 738 | `remembers' its direction: when the cluster decays, the hadron carrying |
| 739 | its flavour continues in the same direction (in the cluster c.m. frame) |
| 740 | as the quark. This considerably hardens the spectrum of heavy hadrons, |
| 741 | particularly of c- and b-flavoured hadrons. It also introduces a tendency |
| 742 | for baryon-antibaryon pairs preferentially to align themselves with the |
| 743 | event axis (the `TPC/2gamma string effect'). |
| 744 | |
| 745 | - The functionality of the routine HWUINE has now been split between it |
| 746 | and a new routine, HWUFNE. A call to the latter MUST be inserted into |
| 747 | the users main program, between the calls to HWMEVT and HWANAL. A |
| 748 | check is built in to version 5.7 to prevent execution if this change |
| 749 | is not made. See the documentation file for an example main program. |
| 750 | We should also take this opportunity to remind users that the analysis |
| 751 | routine HWANAL should begin with the line |
| 752 | IF (IERROR.NE.0) RETURN |
| 753 | since if an event is cancelled, each of the routines is still called |
| 754 | in turn until reaching the end of the main loop. |
| 755 | |
| 756 | - If the new flag USECMF is .TRUE. (the default), events are boosted to |
| 757 | their centre-of-mass frame before processing if necessary, and boosted |
| 758 | back afterwards. This second boost is performed by the new routine |
| 759 | HWUFNE, so it is essential that this is inserted in the correct place, |
| 760 | as described above. |
| 761 | |
| 762 | - In hadronic processes with lepton beams (eg photoproduction in ep), |
| 763 | the lepton->lepton+photon vertex now uses the full tranverse-momentum- |
| 764 | dependent splitting function, with exact light-cone kinematics (i.e. |
| 765 | the Equivalent Photon instead of the Weizsacker-Williams approximation). |
| 766 | This means that the photon-hadron collision has a transverse momentum |
| 767 | in the lepton-hadron frame, and must be boosted to a frame where it |
| 768 | has no transverse momentum. Thus the cmf boost described above is |
| 769 | always used in these processes, regardless of the value of USECMF. |
| 770 | The correct lower energy cut-off appropriate to the hadronic process |
| 771 | is applied to the photon, rather than the fixed cut of 5 GeV that |
| 772 | was used in previous versions. The Q**2 of the photon is generated |
| 773 | within the kinematically allowed limits, or the user-defined limits |
| 774 | Q2WWMN and Q2WWMX (defaults 0 and 4) whichever is more restrictive. |
| 775 | The momentum fraction is generated within the kinematic limits or |
| 776 | between YBMIN and YBMAX (defaults 0 and 1). |
| 777 | |
| 778 | - Point-like photon processes (IPROC=5***) are now also available with |
| 779 | lepton beams, using the Equivalent Photon Approximation. |
| 780 | |
| 781 | - Several minor improvements have been made to the O(as) processes in |
| 782 | DIS (IPROC=91**): |
| 783 | - A sign error has been corrected that led to the incorrect sign for |
| 784 | the lepton-jet azimuthal correlation in QCD Compton processes. |
| 785 | - An additional cut on the phase-space generation has been provided: |
| 786 | the Bjorken-y variable (=Q^2/xs) is limited to range [YBMIN,YBMAX]. |
| 787 | - BGSHAT=.FALSE. is now the default. |
| 788 | - J/Psi production (IPROC=9107) now uses the EPA instead of the WWA, |
| 789 | with the same phase-space cuts as hadronic processes with lepton |
| 790 | beams, see above. |
| 791 | |
| 792 | - Many bugs have been fixed in the other O(as) process routines, HWHDOA |
| 793 | and HWHDOM, ie for IPROC=92**. However, this process is no longer |
| 794 | supported, and is only retained for comparative purposes. It will be |
| 795 | withdrawn completely at the next version release. |
| 796 | |
| 797 | - An interface is now provided to Mark Gibbs' HERBVI package for baryon- |
| 798 | number violation, and other multi-W production processes, IPROC=7***. |
| 799 | |
| 800 | - Minor bug fixes in HWHDIS, HWHEGW and HWHIGW and minor improvements in |
| 801 | HWHHVY, HWHPHO, HWHQCD and HWHWEX hard process routines. |
| 802 | |
| 803 | - New fictional e+e- processes: e+e- -> gluon+gluon(+gluon), IPROC=107 |
| 804 | & 127, treated just like e+e- -> quark+antiquark, summed over light |
| 805 | quark flavours, for direct comparisons between quark and gluon jets. |
| 806 | |
| 807 | - New logical variable PRNDEC (default=.TRUE. unless NMXHEP>9999) causes |
| 808 | track numbers in event listings to be printed in hexadecimal if.FALSE. |
| 809 | This is necessary for very large events such as those generated by the |
| 810 | HERBVI package (see above). |
| 811 | |
| 812 | - PDFLIB structure functions can now be used for the photon as well as |
| 813 | nucleons. The new variable MODPHO acts just like MODPDF. PDFLIB calls |
| 814 | have also been updated to allow for structure function sets with |
| 815 | flavour-asymmetric sea contributions. |
| 816 | |
| 817 | - A logical inconsistency has been fixed in the decays of clusters to |
| 818 | eta or eta' - previously all mixing was neglected, leading to double- |
| 819 | counting and a significant over-estimate of the number of each. The |
| 820 | new variable ETAMIX gives the eta_8/eta_0 mixing angle in degrees |
| 821 | (default = -20). Rates are not very sensitive to its exact value, as |
| 822 | the eta'/eta suppression is dominated by mass effects in the cluster |
| 823 | model. |
| 824 | |
| 825 | - The maximum weight is now always printed in full precision (needed |
| 826 | to be sure of generating the same events in repeated runs). |
| 827 | |
| 828 | - New constants: GEV2NB=389385 |
| 829 | ALPHEM(1)=1./137(.03599) for Q^2=0. |
| 830 | ALPHEM(2)=1./128 for Q^2~M_W^2 |
| 831 | are introduced in various cross section formulae, and G_Fermi is |
| 832 | eliminated. |
| 833 | |
| 834 | - The default top quark mass was increased to 150 GeV. |
| 835 | |
| 836 | In version 5.8 |
| 837 | |
| 838 | * A hard matrix element correction has been introduced in DIS (IPROC = |
| 839 | 90**). This is switched on and off by the logical variable HARDME |
| 840 | (default = .TRUE.). The method is essentially identical to the e+e- |
| 841 | correction, generating first order matrix-element events in a |
| 842 | phase-space region complementary to that of the parton shower. The |
| 843 | e+e- correction is also now controlled by HARDME for consistency. |
| 844 | |
| 845 | * Soft matrix element corrections have been introduced in DIS and e+e- |
| 846 | processes. These correct the distribution of emissions within the |
| 847 | parton shower phase-space. It is similar to the method used in |
| 848 | JETSET, except that the HARDEST emission is matched to the leading |
| 849 | order matrix element, not the first as in JETSET. This ensures that |
| 850 | the correction enters into the form factor, and not just the real |
| 851 | emission probability. |
| 852 | |
| 853 | * In the backward evolution of initial-state radiation for photons the |
| 854 | anomalous branching q-qbar <-- gamma has been introduced. |
| 855 | |
| 856 | * The treatment of forced branching of gluons and sea (anti-)quarks in |
| 857 | backward evolution has been improved, by allowing it to occur at a |
| 858 | random scale between the space-like cutoff QSPAC and the infrared |
| 859 | cutoff, instead of exactly at QSPAC as before. |
| 860 | A new option ISPAC=2 allows the freezing of structure functions at |
| 861 | the scale QSPAC, while evolution continues to the infrared cutoff. |
| 862 | The default, ISPAC=0 is equivalent to previous versions, in which |
| 863 | perturbative evolution stops at QSPAC. |
| 864 | |
| 865 | * It is now possible to completely switch off initial-state radiation, |
| 866 | by setting NOSPAC =.TRUE. Only the forced splitting of non-valence |
| 867 | partons is generated. The default is (of course) NOSPAC =.FALSE. |
| 868 | |
| 869 | * An option to damp the parton distributions of off mass-shell photons |
| 870 | relative on-shell photons, according to the scheme defined in Drees |
| 871 | and Godbole MAD/PH/819 has been introduced. The adjustable parameter |
| 872 | PHOMAS defines the crossover from the non-suppressed to suppressed |
| 873 | regimes. Recommended values lie in the range QCDLAM to 1 GeV. The |
| 874 | default value PHOMAS=0. corresponds to no suppression as in previous |
| 875 | versions. |
| 876 | |
| 877 | * The interface to PDFLIB version 4 has been slightly changed. Instead |
| 878 | of indicating a PDF set by a unique number, an `author group' string |
| 879 | and set number are required. PDFLIB version 3 can still be used from |
| 880 | HERWIG, simply by setting the author group to 'MODE'. It is also now |
| 881 | possible to independently set the PDF set for each of the two beams. |
| 882 | For example, if you previously used MRS D- for the proton and Gordon |
| 883 | -Storrow set 1 for the photon, by setting |
| 884 | MODPDF=47 |
| 885 | MODPHO=231 |
| 886 | You should now set |
| 887 | AUTPDF(2)='MRS' |
| 888 | MODPDF(2)=28 |
| 889 | AUTPDF(1)='GS' |
| 890 | MODPDF(1)=2 |
| 891 | Alternatively, if you are still using PDFLIB version 3, you can set |
| 892 | AUTPDF(2)='MODE' |
| 893 | MODPDF(2)=47 |
| 894 | AUTPDF(1)='MODE' |
| 895 | MODPDF(1)=231 |
| 896 | |
| 897 | * In the CLDIR=1 option for cluster decays a new parameter CLSMR |
| 898 | (default = 0.) allows a Gaussian smearing of the direction of the |
| 899 | perturbative quark's momentum. The smearing is actually exponential |
| 900 | in 1-cos(theta) with mean CLSMR. Thus increasing CLSMR decorrelates |
| 901 | the cluster decay from the initial quark direction. |
| 902 | |
| 903 | * New subprocess have been added: |
| 904 | |
| 905 | - The direct, higher twist, production of light (u,d,s) L=0 mesons |
| 906 | by point-like photons is now available: IPROC = 5500 all Spin =0,1 |
| 907 | mesons, = 5510 only S=0 mesons; = 5520 only S=1 mesons. The vector |
| 908 | mesons are produced with transverse or longitudinal polarisation |
| 909 | |
| 910 | and decayed accordingly. |
| 911 | |
| 912 | - High transverse momentum, scalar Higgs production, in association |
| 913 | with a jet, is now available as IPROC =2300. Only the top quark is |
| 914 | included in the loops with IAPHIG controlling the approx. used: =0 |
| 915 | zero top mass limit; = 1 exact result; = 2 infinite top mass limit |
| 916 | (default 1). Note the routines: HWHGJ1, HWHGJA, HWHGJB/C/D, HWUCI2 |
| 917 | and HWULI2 use (non-standard FORTRAN-77) DOUBLE COMPLEX variables |
| 918 | which may not be accepted by some compilers. Users can change to |
| 919 | COMPLEX variables, however this involves a risk of rounding errors |
| 920 | spoiling numerical cancellations. |
| 921 | |
| 922 | - DIS with neutrino beams is now available in processes IPROC= 90**. |
| 923 | |
| 924 | * The DIS O(alpha_s) jet production processes, IPROC = 92**, have been |
| 925 | withdrawn and are no longer supported. |
| 926 | |
| 927 | * A running electromagnetic coupling has been introduced, HWUAEM(Q2). |
| 928 | ALPHEM (now a single variable) sets the Thomson limit (Q2=0) value, |
| 929 | default = 0.0072993 (1/137.0). |
| 930 | |
| 931 | * Two new particles have been created: 'REMG', IDHW=71, IDHEP=9998 and |
| 932 | 'REMN', IDHW=72, IDHEP=9999 are remnant photons and nucleons |
| 933 | respectively. They are identical to photons & nucleons, except that |
| 934 | gluons are labelled as valence partons and, for the nucleon, valence |
| 935 | quark distributions are set to zero. They are used internally by the |
| 936 | JIMMY generator for multiple interactions, and are not intended for |
| 937 | general use. |
| 938 | |
| 939 | * An error in setting the scale EMCMF (now called EMSCA) for QCD |
| 940 | decays of colour neutral particles, preventing parton showers, has |
| 941 | been corrected. |
| 942 | |
| 943 | * Minor bugs have been corrected in: phi decays to neutral kaons; the |
| 944 | weights for photo-production processes; the value of EVWGT in di-jet |
| 945 | production by point-like photons. |
| 946 | |
| 947 | * The transverse momentum cutoff for final-state photon emission from |
| 948 | quarks, VPCUT, now defaults to 0.4 GeV. Previous versions defaulted |
| 949 | to SQRT(S), switching off such emission. |
| 950 | |
| 951 | * The default top quark mass has been increased to 170 GeV/c^2 |
| 952 | |
| 953 | |
| 954 | ------------------------------------------------------------------------ |
| 955 | |
| 956 | ****** 3. FEATURES NOT YET INCLUDED ****** |
| 957 | |
| 958 | Note that the following features are NOT yet included in the program: |
| 959 | polarization of produced heavy quarks and leptons; treatment of |
| 960 | coherence in the small-x region of incoming jets (see S. Catani, |
| 961 | F. Fiorani and G. Marchesini, Nucl.Phys. B336(1990)18); multiple |
| 962 | parton interactions and parton shadowing; diffractive processes; |
| 963 | W/Z bosons within parton showers. |
| 964 | |
| 965 | ------------------------------------------------------------------------ |
| 966 | |
| 967 | ****** 4. PROGRAM STRUCTURE ****** |
| 968 | |
| 969 | The main program HWIGPR has the following form: |
| 970 | |
| 971 | PROGRAM HWIGPR |
| 972 | C---COMMON BLOCKS ARE INCLUDED AS FILE HERWIG59.INC |
| 973 | INCLUDE 'HERWIG59.INC' |
| 974 | INTEGER N |
| 975 | C---MAX NUMBER OF EVENTS THIS RUN |
| 976 | MAXEV=100 |
| 977 | C---BEAM PARTICLES |
| 978 | PART1='PBAR' |
| 979 | PART2='P' |
| 980 | C---BEAM MOMENTA |
| 981 | PBEAM1=900. |
| 982 | PBEAM2=900. |
| 983 | C---PROCESS |
| 984 | IPROC=1500 |
| 985 | C---INITIALISE OTHER COMMON BLOCKS |
| 986 | CALL HWIGIN |
| 987 | C---USER CAN RESET PARAMETERS AT |
| 988 | C THIS POINT, OTHERWISE DEFAULT |
| 989 | C VALUES IN HWIGIN WILL BE USED. |
| 990 | PTMIN=100. |
| 991 | C---COMPUTE PARAMETER-DEPENDENT CONSTANTS |
| 992 | CALL HWUINC |
| 993 | C---CALL HWUSTA TO MAKE ANY PARTICLE STABLE |
| 994 | CALL HWUSTA('PI0 ') |
| 995 | C---USER'S INITIAL CALCULATIONS |
| 996 | CALL HWABEG |
| 997 | C---INITIALISE ELEMENTARY PROCESS |
| 998 | CALL HWEINI |
| 999 | C---LOOP OVER EVENTS |
| 1000 | DO 100 N=1,MAXEV |
| 1001 | C---INITIALISE EVENT |
| 1002 | CALL HWUINE |
| 1003 | C---GENERATE HARD SUBPROCESS |
| 1004 | CALL HWEPRO |
| 1005 | C---GENERATE PARTON CASCADES |
| 1006 | CALL HWBGEN |
| 1007 | C---DO HEAVY QUARK DECAYS |
| 1008 | CALL HWDHQK |
| 1009 | C---DO CLUSTER FORMATION |
| 1010 | CALL HWCFOR |
| 1011 | C---DO CLUSTER DECAYS |
| 1012 | CALL HWCDEC |
| 1013 | C---DO UNSTABLE PARTICLE DECAYS |
| 1014 | CALL HWDHAD |
| 1015 | C---DO HEAVY FLAVOUR HADRON DECAYS |
| 1016 | CALL HWDHVY |
| 1017 | C---ADD SOFT UNDERLYING EVENT IF NEEDED |
| 1018 | CALL HWMEVT |
| 1019 | C---FINISH EVENT |
| 1020 | CALL HWUFNE |
| 1021 | C---USER'S EVENT ANALYSIS |
| 1022 | CALL HWANAL |
| 1023 | 100 CONTINUE |
| 1024 | C---TERMINATE ELEMENTARY PROCESS |
| 1025 | CALL HWEFIN |
| 1026 | C---USER'S TERMINAL CALCULATIONS |
| 1027 | CALL HWAEND |
| 1028 | STOP |
| 1029 | END |
| 1030 | |
| 1031 | Various phases of the simulation can be suppressed by deleting the |
| 1032 | corresponding subroutine calls, or different subroutines may be |
| 1033 | substituted. For example, in studies at the parton level everything |
| 1034 | from CALL HWDHQK to CALL HWMEVT can be omitted. |
| 1035 | |
| 1036 | The following is a full list of subroutines and functions, which are |
| 1037 | classified according to their initial letters, except when standard- |
| 1038 | ization agreements take precedence. |
| 1039 | |
| 1040 | +--------+---------------------------------------------+ |
| 1041 | | Name | Description | |
| 1042 | +--------+---------------------------------------------+ |
| 1043 | | Main program and initialization | |
| 1044 | +--------+---------------------------------------------+ |
| 1045 | | HWIGPR | Main program | |
| 1046 | | HWIGIN | Default initializations | |
| 1047 | +--------+---------------------------------------------+ |
| 1048 | | Reading/writing/altering decay modes | |
| 1049 | +--------+---------------------------------------------+ |
| 1050 | | HWIODK | Inputs/outputs formatted decay tables | |
| 1051 | | HWMODK | Modifies or adds an individual decay mode | |
| 1052 | +--------+---------------------------------------------+ |
| 1053 | | User-provided analysis routines | |
| 1054 | +--------+---------------------------------------------+ |
| 1055 | | HWABEG | Initializes user's analysis | |
| 1056 | | HWAEND | Terminates user's analysis | |
| 1057 | | HWANAL | Performs user's analysis on event | |
| 1058 | +--------+---------------------------------------------+ |
| 1059 | | Parton branching with interfering gluons | |
| 1060 | +--------+---------------------------------------------+ |
| 1061 | | HWBAZF | Computes azimuthal correlation functions | |
| 1062 | | HWBCON | Makes colour connections between jets | |
| 1063 | | HWBDED | Correction to the `dead zone' in e+e- | |
| 1064 | | HWBDIS | Correction to the `dead zone' in DIS | |
| 1065 | | HWBFIN | Transfers external lines of jet to /HEPEVT/ | |
| 1066 | | HWBGEN | Finds unevolved partons and generates jets | |
| 1067 | | HWBJCO | Combines jets with correct kinematics | |
| 1068 | | HWBMAS | Computes masses and trans. momenta in jet | |
| 1069 | | HWBRAN | Generates a timelike parton branching | |
| 1070 | | HWBSPA | Computes momenta in spacelike jet | |
| 1071 | | HWBSPN | Computes spin density/decay matrices | |
| 1072 | | HWBSU1 | First term in quark Sudakov form factor | |
| 1073 | | HWBSU2 | Second term in quark Sudakov form factor | |
| 1074 | | HWBSUD | Computes (or reads) Sudakov form factors | |
| 1075 | | HWBSUG | Integrand in gluon Sudakov form factor | |
| 1076 | | HWBSUL | Logarithmic part of Sudakov form factor | |
| 1077 | | HWBTIM | Computes momenta in timelike jet | |
| 1078 | | HWBVMC | Virtual mass cutoff for parton type ID | |
| 1079 | +--------+---------------------------------------------+ |
| 1080 | | Cluster hadronization model | |
| 1081 | +--------+---------------------------------------------+ |
| 1082 | | HWCCUT | Cuts a massive cluster in two | |
| 1083 | | HWCDEC | Decays clusters into primary hadrons | |
| 1084 | | HWCFLA | Sets up flavours for HWCHAD | |
| 1085 | | HWCFOR | Forms clusters | |
| 1086 | | HWCGSP | Splits gluons | |
| 1087 | | HWCHAD | Decays a cluster into one or two hadrons | |
| 1088 | +--------+---------------------------------------------+ |
| 1089 | | Particle and heavy quark decays | |
| 1090 | +--------+---------------------------------------------+ |
| 1091 | | HWDBOS | Finds and decays W and Z bosons | |
| 1092 | | HWDBOZ | Chooses decay mode of W and Z bosons | |
| 1093 | | HWDCLE | Interface to CLEO package for B decays | |
| 1094 | | HWDCHK | Checks given decay mode is self-consistent | |
| 1095 | | HWDFOR | Generates a four-body decay | |
| 1096 | | HWDFIV | Generates a five-body decay | |
| 1097 | | HWDEUR | Interface to EURODEC package for B decays | |
| 1098 | | HWDHAD | Generates decays of unstable hadrons | |
| 1099 | | HWDHGC | Higgs -> gamma gamma decay | |
| 1100 | | HWDHGF | Higgs -> W+ W- decay | |
| 1101 | | HWDHIG | Finds and decays Higgs bosons | |
| 1102 | | HWDHQK | Finds and decays heavy quarks | |
| 1103 | | HWDHVY | Finds and decays heavy flavour hadrons | |
| 1104 | | HWDIDP | Chooses a parton for HWDHVY | |
| 1105 | | HWDPWT | Phase space decay weight | |
| 1106 | | HWDTHR | Generates a three-body decay | |
| 1107 | | HWDTOP | Decides whether to decay top quark | |
| 1108 | | HWDTWO | Generates a two-body decay | |
| 1109 | | HWDWWT | Weak (V-A) decay weight | |
| 1110 | | HWDXLM | Tests if decay vertex lies in given volume | |
| 1111 | +--------+---------------------------------------------+ |
| 1112 | | Elementary subprocess generation | |
| 1113 | +--------+---------------------------------------------+ |
| 1114 | | HWEFIN | Final calculations on elementary subprocess | |
| 1115 | | HWEGAM | Generates Weizsacker-Williams photon | |
| 1116 | | HWEINI | Initializes elementary subprocess | |
| 1117 | | HWEISR | Generates a photon fron initial e or mu | |
| 1118 | | HWEONE | Sets up a 2->1 hard subprocess | |
| 1119 | | HWEPRO | Generates elementary subprocess | |
| 1120 | | HWETWO | Sets up a 2->2 hard subprocess | |
| 1121 | +--------+---------------------------------------------+ |
| 1122 | | Individual hard subprocesses | |
| 1123 | +--------+---------------------------------------------+ |
| 1124 | | HWHBGF | Hard subprocess: boson-gluon fusion (BGF) | |
| 1125 | | HWHBKI | Computes kinematics for BGF | |
| 1126 | | HWHBRN | Returns a phase-space point for BGF | |
| 1127 | | HWHBSG | Computes cross section for BGF | |
| 1128 | | HWHDIS | Hard subprocess: deep inelastic lepton quark| |
| 1129 | | HWHDYP | Hard subprocess: Drell-Yan Z0/photon prodn | |
| 1130 | | HWHEGG | Hard subprocess: two-photon processes in ee | |
| 1131 | | HWHEGW | Hard subprocess: photon-W processes in e+e- | |
| 1132 | | HWHEGX | Calculates cross section for HWHEGW | |
| 1133 | | HWHEPA | Hard subprocess: e+e- -> f fbar | |
| 1134 | | HWHEPG | Hard subprocess: e+e- -> q qbar gluon | |
| 1135 | | HWHEW0 | e+e- -> W W / Z Z subroutine | |
| 1136 | | HWHEW1 | e+e- -> W W / Z Z subroutine | |
| 1137 | | HWHEW2 | e+e- -> W W / Z Z subroutine | |
| 1138 | | HWHEW3 | e+e- -> W W subroutine | |
| 1139 | | HWHEW4 | e+e- -> W W / Z Z subroutine | |
| 1140 | | HWHEW5 | e+e- -> Z Z subroutine | |
| 1141 | | HWHEWW | Hard subprocess: e+e- -> W W / Z Z | |
| 1142 | | HWHHVY | Hard subprocess: heavy quark production | |
| 1143 | | HWHIG1 | Matrix elements for Higgs + jet production | |
| 1144 | | HWHIGA | Amplitudes squared for Higgs + jet | |
| 1145 | | HWHIGB | Loop integrals for Higgs + jet | |
| 1146 | | HWHIGJ | QCD Higgs + jet production | |
| 1147 | | HWHIGM | Choose Higgs mass for production routines | |
| 1148 | | HWHIGS | Hard subprocess: gg/qqbar -> Higgs | |
| 1149 | | HWHIGT | Computes gg -> Higgs cross section | |
| 1150 | | HWHIGW | Hard subprocess: WW / ZZ -> Higgs | |
| 1151 | | HWHIGY | Computes ee -> Z -> ZH cross section | |
| 1152 | | HWHIGZ | Hard subprocess: ee -> Z -> ZH | |
| 1153 | | HWHPH2 | Hard subprocess: direct photon pairs | |
| 1154 | | HWHPHO | Hard subprocess: direct photon production | |
| 1155 | | HWHPPB | Box contribution to gg->photon photon | |
| 1156 | | HWHPPE | Pointlike photon-parton (fixed flavour) | |
| 1157 | | HWHPPH | Pointlike photon-parton (fixed pair flavour)| |
| 1158 | | HWHPPM | Pointlike photon-parton direct light meson | |
| 1159 | | HWHPPT | Pointlike photon-parton (all flavours) | |
| 1160 | | HWHQPS | Pointlike photon-quark (Compton) scattering | |
| 1161 | | HWHQCD | Hard subprocess: QCD 2->2 | |
| 1162 | | HWHQCP | Identifies QCD 2->2 hard subprocess | |
| 1163 | | HWHREM | Treats hard scattering remnants | |
| 1164 | | HWHSCT | Process extra hard scatterings | |
| 1165 | | HWHSNG | Colour singlet parton scattering | |
| 1166 | | HWHSNM | Colour singlet parton scattering ME | |
| 1167 | | HWHV1J | Hard subprocess W/Z + jet production | |
| 1168 | | HWHWEX | Top production by W exchange | |
| 1169 | | HWHWPR | Hard subprocess: W production | |
| 1170 | +--------+---------------------------------------------+ |
| 1171 | | Soft minimum-bias or underlying event | |
| 1172 | +--------+---------------------------------------------+ |
| 1173 | | HWMEVT | Generates min bias or soft underlying event | |
| 1174 | | HWMLPS | Generates longitudinal phase space | |
| 1175 | | HWMNBI | Computes negative binomial probability | |
| 1176 | | HWMULT | Chooses min bias charged multiplicity | |
| 1177 | | HWMWGT | Calculates weight for minimum bias events | |
| 1178 | +--------+---------------------------------------------+ |
| 1179 | | Random number generators | |
| 1180 | +--------+---------------------------------------------+ |
| 1181 | | HWRAZM | Randomly rotated azimuth | |
| 1182 | | HWREXP | Random number: exponential distribution | |
| 1183 | | HWREXQ | Random number: exp. dist. with cutoff | |
| 1184 | | HWREXT | Random number: exponential transverse mass | |
| 1185 | | HWRGAU | Random number: Gaussian | |
| 1186 | | HWRGEN | Random number generator (l'Ecuyer method) | |
| 1187 | | HWRINT | Random integer | |
| 1188 | | HWRLOG | Random logical | |
| 1189 | | HWRPIP | Random primary interaction point | |
| 1190 | | HWRPOW | Random number: power distribution | |
| 1191 | | HWRUNG | Random number: uniform + Gaussian tails | |
| 1192 | | HWRUNI | Random number: uniform | |
| 1193 | +--------+---------------------------------------------+ |
| 1194 | | Spacelike branching of incoming partons | |
| 1195 | +--------+---------------------------------------------+ |
| 1196 | | HWSBRN | Generates spacelike parton branching | |
| 1197 | | HWSDGG | Drees-Grassie photon str. function (gluon) | |
| 1198 | | HWSDGQ | Drees-Grassie photon str. function (quarks) | |
| 1199 | | HWSFBR | Chooses a spacelike branching | |
| 1200 | | HWSFUN | Hadron structure functions | |
| 1201 | | HWSGAM | Gamma function (for structure functions) | |
| 1202 | | HWSGEN | Generates x values for spacelike partons | |
| 1203 | | HWSGQQ | Inserts g->q qbar part of gluon form factor | |
| 1204 | | HWSSPC | Replaces spacelike partons by spectators | |
| 1205 | | HWSSUD | Sudakov form factor/structure function | |
| 1206 | | HWSTAB | Interpolates in function table (for HWSSUD) | |
| 1207 | | HWSVAL | Checks for valence parton | |
| 1208 | +--------+---------------------------------------------+ |
| 1209 | | Miscellaneous utilities | |
| 1210 | +--------+---------------------------------------------+ |
| 1211 | | HWUAEM | Running electromagnetic coupling constant | |
| 1212 | | HWUAER | Real part of photon self-energy | |
| 1213 | | HWUALF | Two-loop QCD running coupling constant | |
| 1214 | | HWUANT | Finds a particle's antiparticle | |
| 1215 | | HWUBPR | Prints branching data for last parton shower| |
| 1216 | | HWUBST | Boost event record to/from hadron-hadron cmf| |
| 1217 | | HWUCFF | Coefficients for e+e- and DIS cross sections| |
| 1218 | | HWUCI2 | Logarithmic integral Ci_2 | |
| 1219 | | HWUDAT | Block data: particle properties | |
| 1220 | | HWUDKL | Generates decay vertex of unstable particle | |
| 1221 | | HWUDKS | Converts decay modes into internal format | |
| 1222 | | HWUDPR | Prints particle properties and decay modes | |
| 1223 | | HWUECM | Centre-of-mass energy | |
| 1224 | | HWUEDT | Insert or delete entries in the event record| |
| 1225 | | HWUEEC | Computes coefficients for e+e- cross section| |
| 1226 | | HWUEPR | Prints event data | |
| 1227 | | HWUEMV | Moves entries within the event record | |
| 1228 | | HWUFNE | Finishes an event | |
| 1229 | | HWUGAU | Adaptive Gaussian integration | |
| 1230 | | HWUIDT | Translates particle identity codes | |
| 1231 | | HWUINC | Initial parameter-dependent calculations | |
| 1232 | | HWUINE | Initializes an event | |
| 1233 | | HWULB4 | Boost: rest frame -> lab, no masses assumed | |
| 1234 | | HWULDO | Lorentz 4-vector dot product | |
| 1235 | | HWULF4 | Boost: lab frame -> rest, no masses assumed | |
| 1236 | | HWULI2 | Logarithmic integral Li_2 (Spence function) | |
| 1237 | | HWULOB | Lorentz transformation: rest frame -> lab | |
| 1238 | | HWULOF | Lorentz transformation: lab -> rest frame | |
| 1239 | | HWULOR | Multiplies by Lorentz matrix | |
| 1240 | | HWUMAS | Puts mass in 5th component of vector | |
| 1241 | | HWUPCM | Centre-of-mass momentum | |
| 1242 | | HWURAP | Rapidity | |
| 1243 | | HWURES | Computes/prints resonance data | |
| 1244 | | HWUROB | Rotation by inverse of matrix R | |
| 1245 | | HWUROF | Rotation by matrix R | |
| 1246 | | HWUROT | Computes rotation R from vector to z-axis | |
| 1247 | | HWUSOR | Sorts an array in ascending order | |
| 1248 | | HWUSQR | Square root with sign retention | |
| 1249 | | HWUSTA | Makes a particle type stable | |
| 1250 | | HWUTAB | Interpolates in a table | |
| 1251 | | HWUTIM | Checks time remaining (N.B. VAX Fortran) | |
| 1252 | +--------+---------------------------------------------+ |
| 1253 | | Vector manipulation | |
| 1254 | +--------+---------------------------------------------+ |
| 1255 | | HWVDIF | Vector difference | |
| 1256 | | HWVDOT | Vector dot product | |
| 1257 | | HWVEQU | Vector equality | |
| 1258 | | HWVSCA | Vector times scalar | |
| 1259 | | HWVSUM | Vector sum | |
| 1260 | | HWVZRO | Vector zero | |
| 1261 | +--------+---------------------------------------------+ |
| 1262 | | Warning messages and error handling | |
| 1263 | +--------+---------------------------------------------+ |
| 1264 | | HWWARN | Issues warnings and deals with errors | |
| 1265 | +--------+---------------------------------------------+ |
| 1266 | |
| 1267 | N.B. Dummy versions of the external routines |
| 1268 | |
| 1269 | PDFSET STRUCTM |
| 1270 | EUDINI FRAGMT IEUPDG IPDGEU |
| 1271 | DECADD QQINIT QQLMAT |
| 1272 | HVCBVI HVHBVI |
| 1273 | |
| 1274 | should be deleted if the structure function library, EURODEC B decay |
| 1275 | package, CLEO B decay package, or HERBVI (respectively) is linked. |
| 1276 | ------------------------------------------------------------------------ |
| 1277 | |
| 1278 | ****** 5. BEAMS AND PROCESSES ****** |
| 1279 | |
| 1280 | As indicated above, a number of variables must be set in the main |
| 1281 | program to specify what is to be simulated: |
| 1282 | |
| 1283 | |
| 1284 | +----------+----------------------------------+-----------+ |
| 1285 | | Name | Description | Default | |
| 1286 | +----------+----------------------------------+-----------+ |
| 1287 | | PART1 | Type of particle in beam 1 | 'PBAR '| |
| 1288 | | PART2 | Type of particle in beam 2 | 'P '| |
| 1289 | | PBEAM1 | Momentum of beam 1 | 900. | |
| 1290 | | PBEAM2 | Momentum of beam 2 | 900. | |
| 1291 | | IPROC | Type of process to generate | 1500 | |
| 1292 | | MAXEV | Number of events to generate | 100 | |
| 1293 | +----------+----------------------------------+-----------+ |
| 1294 | |
| 1295 | |
| 1296 | The beam particle types PART1,PART2 supported at present are: |
| 1297 | |
| 1298 | |
| 1299 | +---------------------------------------------+ |
| 1300 | | 'E+ ','E- ','MU+ ','MU- ' | |
| 1301 | | 'NUE ','NUEB ','NUMU ','NMUB ' | |
| 1302 | | 'NTAU ','NTAB ','GAMA ' | |
| 1303 | | 'P ','PBAR ','N ','NBAR ' | |
| 1304 | | 'PI+ ','PI- ' | |
| 1305 | +---------------------------------------------+ |
| 1306 | |
| 1307 | In addition, beams 'K+ ' and 'K- ' are supported for |
| 1308 | minimum bias non-diffractive soft hadronic events (IPROC=8000) only. |
| 1309 | |
| 1310 | The currently available processes IPROC are tabulated below. |
| 1311 | |
| 1312 | +---------+--------------------------------------------------------+ |
| 1313 | | IPROC | Process | |
| 1314 | +---------+--------------------------------------------------------+ |
| 1315 | | 100 | e+ e- -> q qbar (gluon) (all flavours) | |
| 1316 | | 100+IQ | e+ e- -> q qbar (gluon) (IQ=1--6 for q=d,u,s,c,b,t) | |
| 1317 | | 107 | e+ e- -> gluon gluon (gluon) fictitious process | |
| 1318 | | 110 | e+ e- -> q qbar gluon (all flavours) | |
| 1319 | | 110+IQ | e+ e- -> q qbar gluon (IQ as above) | |
| 1320 | | 120 | e+ e- -> q qbar (all flavours)| without correction to | |
| 1321 | | 120+IQ | e+ e- -> q qbar (IQ as above) | hard gluon branching | |
| 1322 | | 127 | e+ e- -> gluon gluon | | |
| 1323 | | 150+IL | e+ e- -> l lbar (IL=2,3 for l=mu,tau) | |
| 1324 | +---------+--------------------------------------------------------+ |
| 1325 | | 200 | e+ e- -> W+ W- (see sect. 18 on control of W/Z decays)| |
| 1326 | | 250 | e+ e- -> Z0 Z0 (see sect. 18 on control of W/Z decays)| |
| 1327 | +---------+--------------------------------------------------------+ |
| 1328 | | 300 | e+ e- -> Z H -> Z q qbar (all flavours) | |
| 1329 | | 300+IQ | e+ e- -> Z H -> Z q qbar (IQ as above) | |
| 1330 | | 306+IL | e+ e- -> Z H -> Z l lbar (IL=1,2,3 for l=e,mu,tau) | |
| 1331 | | 310,11 | e+ e- -> Z H -> Z W W, Z Z Z | |
| 1332 | | 312 | e+ e- -> Z H -> Z gamma gamma | |
| 1333 | | 399 | e+ e- -> Z H -> Z anything | |
| 1334 | +---------+--------------------------------------------------------+ |
| 1335 | | 400+ID | e+ e- -> nu nu H + e e H (ID as in IPROC=300+ID) | |
| 1336 | +---------+--------------------------------------------------------+ |
| 1337 | | 500+ID | e+ e- -> gamma gamma -> qqbar/llbar/WW (ID=0-10 as in | |
| 1338 | | | IPROC=300+ID) | |
| 1339 | | 550+ID | e+ e- -> gamma W -> qq'bar/ll'bar (ID=0-9) | |
| 1340 | +---------+--------------------------------------------------------+ |
| 1341 | | 1300 | q qbar -> Z0/gamma -> q qbar (all flavours) | |
| 1342 | | 1300+IQ | q qbar -> Z0/gamma -> q qbar (IQ as above) | |
| 1343 | | 1350 | q qbar -> Z0/gamma -> l lbar (all lepton species) | |
| 1344 | | 1350+IL | q qbar -> Z0/gamma -> l lbar (IL=1-6 for e,enu,mu,etc) | |
| 1345 | | 1399 | q qbar -> Z0/gamma -> anything | |
| 1346 | +---------+--------------------------------------------------------+ |
| 1347 | | 1400 | q qbar -> W+/- -> q' qbar'' (all flavours) | |
| 1348 | | 1400+IQ | q qbar -> W+/- -> q' qbar'' (q' or q'' as above) | |
| 1349 | | 1450 | q qbar -> W+/- -> l nul (all lepton species) | |
| 1350 | | 1450+IL | q qbar -> W+/- -> l nul (IL=1-3 as above) | |
| 1351 | | 1499 | q qbar -> W+/- -> anything | |
| 1352 | +---------+--------------------------------------------------------+ |
| 1353 | | 1500 | QCD 2 -> 2 hard parton scattering | |
| 1354 | | | After generation, IHPRO is subprocess (see list) | |
| 1355 | +---------+--------------------------------------------------------+ |
| 1356 | | 1600+ID | q qbar/g g -> Higgs (ID as in IPROC=300+ID) | |
| 1357 | +---------+--------------------------------------------------------+ |
| 1358 | | 1700+IQ | QCD heavy quark production (IQ as above) | |
| 1359 | | | After generation, IHPRO is subprocess (see list) | |
| 1360 | +---------+--------------------------------------------------------+ |
| 1361 | | 1800 | QCD direct photon + jet production | |
| 1362 | | | After generation, IHPRO is subprocess (see list) | |
| 1363 | +---------+--------------------------------------------------------+ |
| 1364 | | 1900+ID | q qbar -> q' qbar' H (ID as in IPROC=300+ID) | |
| 1365 | +---------+--------------------------------------------------------+ |
| 1366 | | 2000 | t production via W exchange (sum of 2001-2008) | |
| 1367 | | 2001,2 | ubar bbar -> dbar tbar, d bbar -> u tbar | |
| 1368 | | 2003,4 | dbar bbar -> ubar tbar, u b -> d t | |
| 1369 | | 2005,6 | cbar bbar -> sbar tbar, s bbar -> c tbar | |
| 1370 | | 2007,8 | sbar b -> cbar t , c b -> s t | |
| 1371 | +---------+--------------------------------------------------------+ |
| 1372 | | 2100 | Vector boson + jet production. | |
| 1373 | | 2110,20 | Compton only (g q -> V q), annih. only (q qbar -> V g) | |
| 1374 | +---------+--------------------------------------------------------+ |
| 1375 | | 2200 | QCD direct photon pair production (see list for IHPRO) | |
| 1376 | +---------+--------------------------------------------------------+ |
| 1377 | | 2300 | QCD Higgs plus jet production (see list for IHPRO) | |
| 1378 | +---------+--------------------------------------------------------+ |
| 1379 | | 2400 | Mueller-Tang colour singlet exchange | |
| 1380 | | 2450 | Quark scattering via photon exchange | |
| 1381 | +---------+--------------------------------------------------------+ |
| 1382 | | 5000 | Pointlike photon-hadron jet production (all flavours) | |
| 1383 | | 5100+IQ | Pointlike photon heavy flavour IQ pair production | |
| 1384 | | 5200+IQ | Pointlike photon heavy flavour IQ single excitation | |
| 1385 | | | After generation, IHPRO is subprocess (see list) | |
| 1386 | | 5300 | Quark photon Compton scattering | |
| 1387 | | 5500 | Pointlike photon production of light (u,d,s) L=0 mesons| |
| 1388 | | 5510,20 | S=0 mesons only, S=1 mesons only (see list for IHPRO) | |
| 1389 | +---------+--------------------------------------------------------+ |
| 1390 | | 7000 - | Baryon-number violating and other multi-W processes | |
| 1391 | | 7999 | generated by HERBVI package | |
| 1392 | +---------+--------------------------------------------------------+ |
| 1393 | | 8000 | Minimum bias non-diffractive soft hadron-hadron event | |
| 1394 | +---------+--------------------------------------------------------+ |
| 1395 | | 9000 | Deep inelastic lepton scattering (all neutral current) | |
| 1396 | | 9000+IQ | Deep inelastic lepton scattering (NC on flavour IQ) | |
| 1397 | | 9010 | Deep inelastic lepton scattering (all charged current) | |
| 1398 | | 9010+IQ | Deep inelastic lepton scattering (CC on flavour IQ) | |
| 1399 | +---------+--------------------------------------------------------+ |
| 1400 | | 9100 | Boson-gluon fusion in NC DIS, all flavours | |
| 1401 | | 9100+IQ | Boson-gluon fusion in NC DIS, IQ=1-6 as above | |
| 1402 | | 9107 | J/Psi + gluon production by boson-gluon fusion | |
| 1403 | | 9110 | QCD Compton process in NC DIS, all flavours | |
| 1404 | | 9110+IP | QCD Compton process in NC DIS, IP=1-12, d-t, dbar-tbar | |
| 1405 | | 9130 | All O(alpha-s) NC processes: 9100+9110 | |
| 1406 | | 9140+IP | CC proc, IP:1 = s cbar,2 = b cbar,3 = s tbar,4 = b tbar| |
| 1407 | +---------+--------------------------------------------------------+ |
| 1408 | | 92** | Withdrawn: use 91** instead | |
| 1409 | +---------+--------------------------------------------------------+ |
| 1410 | | 9500+ID | W W fusion -> Higgs in e p (ID as in IPROC=300+ID) | |
| 1411 | +---------+--------------------------------------------------------+ |
| 1412 | |10000+IP | as IPROC=IP but with soft underlying event (hadron | |
| 1413 | | | remnant fragmentation in lepton-hadron) suppressed | |
| 1414 | +---------+--------------------------------------------------------+ |
| 1415 | |
| 1416 | The extent to which quark mass effects are included in the hard |
| 1417 | process cross section is different in different processes. In many |
| 1418 | processes, they are always treated as massless: IPROC=1300, 1800, |
| 1419 | 1900, 2100, 2300, 2400, 5300, 9000. In two processes they are all |
| 1420 | treated as massless except the top quark, for which the mass is |
| 1421 | correctly incorporated: 1400, 2000. In the case of massless pair |
| 1422 | production, only quark flavours that are kinematically allowed are |
| 1423 | produced. In all cases the event kinematics incorporate the quark |
| 1424 | mass, even when it is not used to calculate the cross section. |
| 1425 | |
| 1426 | In two processes, quarks are always treated as massive: 500, 9100. |
| 1427 | |
| 1428 | Finally, in several processes, the behaviour is different depending |
| 1429 | on whether a specific quark flavour is requested, in which case its |
| 1430 | mass is included, or not, in which case all quarks are treated as |
| 1431 | massless. These are: IPROC=100, 110, 120, QCD 2->2 scattering |
| 1432 | (1500 vs 1700+IQ), jets in direct photoproduction (5000 vs 5100+IQ |
| 1433 | and 5200+IQ). |
| 1434 | |
| 1435 | These differences can cause inconsistencies between different ways |
| 1436 | of generating the same process. The most noticeable example is in |
| 1437 | direct photoproduction, where one can use process 9130, which uses |
| 1438 | the exact 2->3 matrix element e+g --> e+q+qbar, or process 5000, |
| 1439 | which uses the Weizsacker-Williams spectrum for e --> e+gamma and |
| 1440 | the 2->2 matrix element for gamma+g --> q+qbar. For typical HERA |
| 1441 | kinematics, the W-W approximation is valid to a few per cent, but |
| 1442 | the difference between the two processes is much larger, about 20% |
| 1443 | for PTMIN=2 GeV. This is entirely due to the difference in quark |
| 1444 | mass treatments, as can be checked by comparing process 9130 with |
| 1445 | processes 5100+IQ and 5200+IQ summed over IQ |
| 1446 | ------------------------------------------------------------------------ |
| 1447 | |
| 1448 | ****** 6. INPUT PARAMETERS ****** |
| 1449 | |
| 1450 | The quantities that may be regarded as adjustable parameters are |
| 1451 | |
| 1452 | +----------+----------------------------------+-------+ |
| 1453 | | Name | Description |Default| |
| 1454 | +----------+----------------------------------+-------+ |
| 1455 | | QCDLAM | QCD Lambda (see below) | 0.18 | |
| 1456 | +----------+----------------------------------+-------+ |
| 1457 | | RMASS(1) | Down quark mass | 0.32 | |
| 1458 | | RMASS(2) | Up quark mass | 0.32 | |
| 1459 | | RMASS(3) | Strange quark mass | 0.50 | |
| 1460 | | RMASS(4) | Charmed quark mass | 1.55 | |
| 1461 | | RMASS(5) | Bottom quark mass | 4.95 | |
| 1462 | | RMASS(6) | Top quark mass | 170. | |
| 1463 | +----------+----------------------------------+-------+ |
| 1464 | | RMASS(13)| Gluon effective mass | 0.75 | |
| 1465 | +----------+----------------------------------+-------+ |
| 1466 | | VQCUT | Quark virtuality cutoff (added to| 0.48 | |
| 1467 | | | quark masses in parton showers) | | |
| 1468 | | VGCUT | Gluon virtuality cutoff (added to| 0.10 | |
| 1469 | | | effective mass in parton showers)| | |
| 1470 | | VPCUT | Photon virtuality cutoff | 0.40 | |
| 1471 | +----------+----------------------------------+-------+ |
| 1472 | | CLMAX | Maximum cluster mass parameter | 3.35 | |
| 1473 | | CLPOW | Power in maximum cluster mass | 2.00 | |
| 1474 | | PSPLT | Split cluster spectrum parameter | 1.00 | |
| 1475 | +----------+----------------------------------+-------+ |
| 1476 | | QDIQK | Maximum scale for gluon->diquarks| 0.00 | |
| 1477 | | PDIQK | Gluon->diquarks rate parameter | 5.00 | |
| 1478 | +----------+----------------------------------+-------+ |
| 1479 | | QSPAC | Cutoff for spacelike evolution | 2.50 | |
| 1480 | | PTRMS | Intrinsic pt in incoming hadrons | 0.00 | |
| 1481 | +----------+----------------------------------+-------+ |
| 1482 | |
| 1483 | Notes on parameters: |
| 1484 | |
| 1485 | * QCDLAM can be identified at high momentum fractions (x or z) with |
| 1486 | the fundamental QCD scale Lambda-MSbar (5 flavours). However, this |
| 1487 | relation does not necessarily hold in other regions of phase space, |
| 1488 | since higher order corrections are not treated precisely enough to |
| 1489 | remove renormalization scheme ambiguities. See S. Catani, G. March- |
| 1490 | esini and B.R.Webber, Nucl. Phys. B349 (1991) 635. |
| 1491 | |
| 1492 | * RMASS(1,2,3,13) are effective light quark and gluon masses used in |
| 1493 | the hadronization phase of the program. They can be set to zero |
| 1494 | provided the parton shower cutoffs VQCUT and VGCUT are large enough |
| 1495 | to prevent divergences (see below). |
| 1496 | |
| 1497 | * For cluster hadronization, it must be possible to split gluons into |
| 1498 | q-qbar, i.e. RMASS(13) must be at least twice the lightest quark |
| 1499 | mass. Similarly it may be impossible for heavy flavoured clusters |
| 1500 | to decay if RMASS(4,5) are too low. |
| 1501 | |
| 1502 | * VQCUT and VGCUT are needed if the quark and gluon effective masses |
| 1503 | become small. The condition to avoid divergences in parton showers |
| 1504 | is |
| 1505 | 1/Q(i) + 1/Q(j) < 1/QCDL3 for either i or j or both gluons, |
| 1506 | where Q(i)=RMASS(i)+VQCUT for quarks, RMASS(13)+VGCUT for gluons, |
| 1507 | and QCDL3 is the equivalent 3-flavour Lambda computed from QCDLAM. |
| 1508 | In the notation of the above reference by S. Catani et al., QCDL3 |
| 1509 | is the 3-flavour equivalent of QCDL5 where |
| 1510 | QCDL5 = QCDLAM*exp(K/(4*pi*beta))/sqrt(2)=1.109*QCDLAM |
| 1511 | |
| 1512 | * VPCUT is the analogous quantity for photon emission. It defaults to |
| 1513 | SQRT(S) corresponding to no emission. Results after experimental |
| 1514 | cuts are insensitive to its exact value in the range 0.1 to 1.0 GeV |
| 1515 | |
| 1516 | * CLMAX and CLPOW determine the maximum allowed mass of a cluster |
| 1517 | made from quarks i and j as follows |
| 1518 | Mass**CLPOW < CLMAX**CLPOW + (RMASS(i)+RMASS(j))**CLPOW |
| 1519 | Since the cluster mass spectrum falls rapidly at high mass, results |
| 1520 | become insensitive to CLMAX and CLPOW at large values of CLMAX. |
| 1521 | Smaller values OF CLPOW will increase the yield of heavier clusters |
| 1522 | (and hence of baryons) for heavy quarks, without affecting light |
| 1523 | quarks much. For example, the default value gives no b-baryons |
| 1524 | whereas CLPOW=1.0 makes b-baryons/b-hadrons about 1/4. |
| 1525 | |
| 1526 | * PSPLT determines the mass distribution in the cluster splitting |
| 1527 | CL1 -> CL2 + CL3 when CL1 is above the maximum allowed mass. The |
| 1528 | masses of CL2 and CL3 are generated uniformly in Mass**PSPLT. Since |
| 1529 | the number of split clusters is small, dependence on PSPLT is weak. |
| 1530 | |
| 1531 | * QDIQK greater than twice the lightest diquark mass enables gluons |
| 1532 | to split non-perturbatively into diquarks as well as quarks. The |
| 1533 | probability of this is PDIQK*dQ/Q for scales Q below QDIQK. The |
| 1534 | diquark masses are taken to be the sum of constituent quark masses. |
| 1535 | Thus the default value QDIQK=0 suppresses gluon->diquark splitting. |
| 1536 | |
| 1537 | * QSPAC is the scale below which the structure functions of incoming |
| 1538 | hadrons are frozen and non-valence constituent partons are forced |
| 1539 | to evolve to valence partons, if ISPAC=0. For ISPAC=2, structure |
| 1540 | functions are frozen at scale QSPAC, but evolution continues down |
| 1541 | to the infrared cutoff. |
| 1542 | |
| 1543 | * PTRMS is the width of the (Gaussian) intrinsic transverse momentum |
| 1544 | distribution of valence partons in incoming hadrons at scale QSPAC. |
| 1545 | (N.B. Neither QSPAC nor PTRMS affect lepton-lepton collisions.) |
| 1546 | |
| 1547 | In practice, the parameters that have been found most effective in |
| 1548 | fitting data are QCDLAM, the gluon effective mass RMASS(13), and the |
| 1549 | cluster mass parameter CLMAX. |
| 1550 | |
| 1551 | The default parameter values have been found to give good agreement |
| 1552 | with event shape distributions at LEP (OPAL preprint CERN-EP/90-48). |
| 1553 | |
| 1554 | A number of further parameters are needed to control the program and |
| 1555 | to turn various options on or off: |
| 1556 | |
| 1557 | +----------+----------------------------------+-------+ |
| 1558 | | Name | Description |Default| |
| 1559 | +----------+----------------------------------+-------+ |
| 1560 | | IPRINT | Printout option | 1 | |
| 1561 | | MAXPR | Number of events to print out | 1 | |
| 1562 | | PRVTX | Include vertex info in print out | .TRUE.| |
| 1563 | | MAXER | Max number of errors | 10 | |
| 1564 | | LWEVT | Unit for writing output events | 0 | |
| 1565 | | LRSUD | Unit for reading Sudakov table | 0 | |
| 1566 | | LWSUD | Unit for writing Sudakov table | 77 | |
| 1567 | | SUDORD | Alpha_s order in Sudakov table | 1 | |
| 1568 | +----------+----------------------------------+-------+ |
| 1569 | | NRN(1) | Random number seed 1 | 17673 | |
| 1570 | | NRN(2) | Random number seed 2 | 63565 | |
| 1571 | | WGTMAX | Max weight (0 to search for it) | 0. | |
| 1572 | | NOWGT | Generate unweighted events | .TRUE.| |
| 1573 | +----------+----------------------------------+-------+ |
| 1574 | | AZSOFT | Soft gluon azimuthal correlations| .TRUE.| |
| 1575 | | AZSPIN | Gluon spin azimuthal correlations| .TRUE.| |
| 1576 | +----------+----------------------------------+-------+ |
| 1577 | | NCOLO | Number of colours | 3 | |
| 1578 | | NFLAV | Number of (producible) flavours | 6 | |
| 1579 | +----------+----------------------------------+-------+ |
| 1580 | | MODPDF(I)| PDFLIB structure function set and| -1 | |
| 1581 | | AUTPDF(I)| author group for beam I(=1,2) | 'MRS' | |
| 1582 | | | (if MODPDF()<0 do not use PDFLIB)| | |
| 1583 | | NSTRU | Input structure function set | 5 | |
| 1584 | | | (1,2=Duke-Owens1,2 3,4=EHLQ1,2 | | |
| 1585 | | | 5=Owens1.1) | | |
| 1586 | +----------+----------------------------------+-------+ |
| 1587 | | ETAMIX | eta/eta' mixing angle in degrees | -20 | |
| 1588 | | | F0Mix.. |
| 1589 | +----------+----------------------------------+-------+ |
| 1590 | | B1LIM | B cluster -> 1 hadron parameter | 0.0 | |
| 1591 | +----------+----------------------------------+-------+ |
| 1592 | | CLDIR | Decay of perturbative clusters, | 1 | |
| 1593 | | | 0=>isotropic, 1=>along quark dirn| | |
| 1594 | | CLSMR | Width of Gaussian angle smearing | 0.0 | |
| 1595 | +----------+----------------------------------+-------+ |
| 1596 | | CLRECO | Include colour rearrangement |.FALSE | |
| 1597 | | PRECO | Probability for rearrangement | 1./9. | |
| 1598 | | EXAG | Lifetime scaling for weak bosons | 1. | |
| 1599 | +----------+----------------------------------+-------+ |
| 1600 | | PIPSMR | Smear the primary vertex | .TRUE.| |
| 1601 | | MAXDKL | Veto decays outside given volume |.FALSE.| |
| 1602 | +----------+----------------------------------+-------+ |
| 1603 | | HARDME | Use hard and soft matrix-element | .TRUE.| |
| 1604 | | SOFTME | corrections to e+e- and DIS | .TRUE.| |
| 1605 | +----------+----------------------------------+-------+ |
| 1606 | | BDECAY | Controls which B Decay package is| 'HERW'| |
| 1607 | | | used. The allowed values are: | | |
| 1608 | | | 'HERW'; 'EURO'; or 'CLEO'. | | |
| 1609 | | MIXING | Include neutral B meson mixing | .TRUE.| |
| 1610 | | XMIX(2) | Mass difference I=1 B^0_s | 10.0 | |
| 1611 | | | average width 2 B^0_d | 0.70 | |
| 1612 | | YMIX(2) | Width difference I=1 B^0_s | 0.20 | |
| 1613 | | | average width 2 B^0_d | 0.00 | |
| 1614 | +----------+----------------------------------+-------+ |
| 1615 | | EPOLN(3) | Electron and positron beam | 0.0 | |
| 1616 | | | polarizations in DIS and e+e- | 0.0 | |
| 1617 | | | annihilation. First two cmpts are| 0.0 | |
| 1618 | | PPOLN(3) | transverse and only used in e+e-,| 0.0 | |
| 1619 | | | 3rd cmpt is longitudinal, and is | 0.0 | |
| 1620 | | | +/-1 for fully rh/lh polarized | 0.0 | |
| 1621 | +----------+----------------------------------+-------+ |
| 1622 | | BGSHAT | Scale=shat for boson-gluon fusion|.FALSE.| |
| 1623 | +----------+----------------------------------+-------+ |
| 1624 | | BREIT | Use Breit frame for DIS kinematix| .TRUE.| |
| 1625 | +----------+----------------------------------+-------+ |
| 1626 | | USECMF | Use hadron-hadron cmf | .TRUE.| |
| 1627 | +----------+----------------------------------+-------+ |
| 1628 | | NOSPAC | Switch off space-like showers |.FALSE.| |
| 1629 | +----------+----------------------------------+-------+ |
| 1630 | | ISPAC | Changes meaning of QSPAC, | 0 | |
| 1631 | | | see the earlier notes on QSPAC | | |
| 1632 | +----------+----------------------------------+-------+ |
| 1633 | | TMNISR | Min vaule shat/S for photon ISR | 1D-4 | |
| 1634 | | ZMXISR | Max mom fraction for photon ISR | 1-1D-6| |
| 1635 | +----------+----------------------------------+-------+ |
| 1636 | | PTMIN | Min pt in hadronic jet production| 10. | |
| 1637 | | PTMAX | Max pt in hadronic jet production| 1.E8 | |
| 1638 | | PTPOW | 1/pt**PTPOW for jet sampling | 4. | |
| 1639 | | YJMIN | Min jet rapidity |-8. | |
| 1640 | | YJMAX | Max jet rapidity | 8. | |
| 1641 | +----------+----------------------------------+-------+ |
| 1642 | | EMMIN | Min dilepton mass in Drell-Yan | 10. | |
| 1643 | | EMMAX | Max dilepton mass in Drell-Yan | 1.E8 | |
| 1644 | | EMPOW | 1/m**EMPOW for Drell-Yan sampling| 4. | |
| 1645 | +----------+----------------------------------+-------+ |
| 1646 | | Q2MIN | Min Q**2 in deep inelastic | 0.0 | |
| 1647 | | Q2MAX | Max Q**2 in deep inelastic | 1.E10 | |
| 1648 | | Q2POW | (1/Q**2)**Q2POW for sampling | 2.5 | |
| 1649 | +----------+----------------------------------+-------+ |
| 1650 | | Q2WWMN | Min Q**2 in Equiv Photon Approx | 0.0 | |
| 1651 | | Q2WWMX | Max Q**2 in Equiv Photon Approx | 4.0 | |
| 1652 | +----------+----------------------------------+-------+ |
| 1653 | | YWWMIN | Min energy of gamma in WW approx | 1.0 | |
| 1654 | | YWWMAX | Max energy of gamma in WW approx | 0.0 | |
| 1655 | +----------+----------------------------------+-------+ |
| 1656 | | PHOMAS | Damp structure functions for off-| 0.0 | |
| 1657 | | | shell photons (0 for no damping) | | |
| 1658 | +----------+----------------------------------+-------+ |
| 1659 | | YBMIN | Min and Max Bjorken-y in DIS and | 0.0 | |
| 1660 | | YBMAX | Equivalent Photon Approx | 1.0 | |
| 1661 | +----------+----------------------------------+-------+ |
| 1662 | | ZJMAX | Max Z in J/psi production | 0.9 | |
| 1663 | +----------+----------------------------------+-------+ |
| 1664 | | THMAX | Max thrust in 3 parton production| 0.9 | |
| 1665 | | | (equal to 1-Y_cut in JADE scheme)| | |
| 1666 | +----------+----------------------------------+-------+ |
| 1667 | |
| 1668 | Printout options are: |
| 1669 | |
| 1670 | IPRINT = 0 Print program title only |
| 1671 | 1 Print selected input parameters |
| 1672 | 2 1 + table of particle codes and properties |
| 1673 | 3 2 + tables of Sudakov form factors |
| 1674 | |
| 1675 | PRVTX = .T. To include the production vertex information in |
| 1676 | the event print out, requires wide screen format. |
| 1677 | |
| 1678 | See sect. 8 on form factors for details of LRSUD, LWSUD and SUDORD. |
| 1679 | |
| 1680 | If BGSHAT is false, the scale used for heavy quark production via |
| 1681 | boson-gluon fusion in lepton-hadron collisions will be |
| 1682 | 2*shat*that*uhat/(shat**2+that**2+uhat**2) |
| 1683 | |
| 1684 | If BREIT is true, the kinematic reconstruction of deep inelastic |
| 1685 | events takes place in the Breit frame (ie. the frame where the |
| 1686 | exchanged boson is purely space-like, and collinear with the |
| 1687 | incoming hadron). In fact the reconstruction procedure is |
| 1688 | invariant under longitudinal boosts, so any frame in which the |
| 1689 | boson and hadron are collinear would be equivalent, and it is only |
| 1690 | the transverse part of the boost that has an effect. |
| 1691 | The BREIT frame option becomes very inaccurate for very small Q^2. |
| 1692 | It is therefore only used if Q**2 > 1E-4 (the lab and Breit frames |
| 1693 | are anyway equivalent for such small Q**2). |
| 1694 | If BREIT is false, reconstruction takes place in the lab frame. |
| 1695 | |
| 1696 | If USECMF is true, the entire event record is boost to the hadron- |
| 1697 | hadron cmf before event processing, and boosted back afterwards. |
| 1698 | This means that fixed-target simulation can be done in the lab |
| 1699 | frame, ie with PBEAM2=0. |
| 1700 | For hadronic processes with lepton beams, this boosting is always |
| 1701 | done, regardless of the value of USECMF. |
| 1702 | |
| 1703 | The interface to the PDFLIB structure function package is |
| 1704 | compatible with PDFLIB versions 3 and 4. For version 4, AUTPDF() |
| 1705 | should be set to the author group as listed in the PDFLIB manual, |
| 1706 | eg 'MRS', and MODPDF() to the set number in the new convention. |
| 1707 | For version 3, AUTPDF() should be set to 'MODE', and MODPDF() to |
| 1708 | the set number in the old convention. |
| 1709 | |
| 1710 | The `hard' matrix-element correction adds e+e- and DIS events in |
| 1711 | regions of phase-space that cannot be filled by the usual parton |
| 1712 | shower. The `soft' matrix-element correction moves emissions |
| 1713 | around within the shower phase-space, essentially by matching |
| 1714 | the HARDEST emission (which is not necessarily the first) to the |
| 1715 | first-order matrix-element. |
| 1716 | |
| 1717 | The quantities from PTMIN onwards control the region of phase |
| 1718 | space in which events are generated and the importance sampling |
| 1719 | inside those regions. See section 11 on event weights for further |
| 1720 | details on these quantities and the use of WGTMAX and NOWGT. |
| 1721 | |
| 1722 | If hadronic processes with lepton beams are requested, the photon |
| 1723 | emission vertex includes the full transverse-momentum-dependent |
| 1724 | kinematics (the Equivalent Photon Approximation). The variables |
| 1725 | Q2WWMN and Q2WWMX set the minimum and maximum virtualities |
| 1726 | generated respectively. For normal simulation, Q2WWMN should be 0, |
| 1727 | and Q2WWMX should be the largest Q**2 through which the lepton can |
| 1728 | be scattered without being detected. The variables YBMIN and |
| 1729 | YBMAX control the range of lightcone momentum fraction generated. |
| 1730 | |
| 1731 | In addition there are options to give different weights to the |
| 1732 | various flavours of quarks and diquarks, and to resonances of |
| 1733 | different spins. So far, these options have not been used. See |
| 1734 | the comments in the initialization routine HWIGIN for details. |
| 1735 | |
| 1736 | ------------------------------------------------------------------------ |
| 1737 | |
| 1738 | ****** 7. COMMON BLOCK FILE ****** |
| 1739 | |
| 1740 | C ****COMMON BLOCK FILE FOR HERWIG VERSION 5.9**** |
| 1741 | C |
| 1742 | C ALTERATIONS: See 5.8 for list of previous revisions |
| 1743 | C Layout completely overhauled |
| 1744 | C |
| 1745 | C The following variables have been removed: |
| 1746 | C FBTM,FTOP,FHVY,VECWT,TENWT,SWT,RESWT |
| 1747 | C MADDR,MODES,MODEF,IDPRO |
| 1748 | C The following COMMON BLOCK has been removed |
| 1749 | C /HWUFHV/ - BDECAY moved to /HWPRCH/ |
| 1750 | C The following COMMON BLOCKs have been added |
| 1751 | C /HWBMCH/ -contains PART1, PART2 from /HWBEAM/ |
| 1752 | C /HWPRCH/ -contains AUTPDF from /HWPARM/ & BDECAY |
| 1753 | C /HWPROP/ -contains many variables from /HWUPDT/ |
| 1754 | C /HWDIST/ -contains variables for mixing and vertices |
| 1755 | C /HWQDKS/ -contains heavy flavour decay information |
| 1756 | C The following variables have been changed to CHARACTER*8: |
| 1757 | C PART1,PART2,RNAME |
| 1758 | C The following parameters have been added: |
| 1759 | C NMXCDK,NMXDKS,NMXMOD,NMXQDK,NMXRES |
| 1760 | C The following variables have been added: |
| 1761 | C CSPEED,F0MIX,F1MIX,F2MIX,H1MIX, |
| 1762 | C PHIMIX,IOPREM,PRVTX see HWPRAM |
| 1763 | C ANOMSC,ISLENT see HWBRCH |
| 1764 | C GAMWT see HWEVNT |
| 1765 | C ASFIXD,OMEGA0,TMNISR,WHMIN,YWWMAX, |
| 1766 | C YWWMIN,ZMXISR,COLISR see HWHARD |
| 1767 | C IFLAV,RLTIM,RSPIN,VTOCDK,VTORDK see HWPROP |
| 1768 | C DKLTM,IDK,IDKPRD,LNEXT,LSTRT, |
| 1769 | C NDKYS,NME,NMODES,NPRODS, |
| 1770 | C DKPSET,RSTAB see HWUPDT |
| 1771 | C REPWT,SNGWT see HWUWTS |
| 1772 | C CLDKWT,CTHRPW,PRECO,NCLDK,CLRECO see HWUCLU |
| 1773 | C EXAG,GEV2MM,HBAR,PLTCUT,VMIN2, |
| 1774 | C VTXPIP,XMIX,XMRCT,YMIX,YMRCT, |
| 1775 | C IOPDKL,MAXDKL,MIXING,PIPSMR see HWDIST |
| 1776 | C VTXQDK,IMQDK,LOCQ,NQDK see HWQDKS |
| 1777 | C |
| 1778 | C |
| 1779 | IMPLICIT NONE |
| 1780 | DOUBLE PRECISION ZERO,ONE,TWO,THREE,FOUR,HALF |
| 1781 | PARAMETER (ZERO =0.D0, ONE =1.D0, TWO =2.D0, |
| 1782 | & THREE=3.D0, FOUR=4.D0, HALF=0.5D0) |
| 1783 | C |
| 1784 | DOUBLE PRECISION |
| 1785 | & ACCUR,AFCH,ALPFAC,ALPHEM,ANOMSC,ASFIXD,AVWGT,B1LIM,BETAF,BRFRAC, |
| 1786 | & BRHIG,BTCLM,CAFAC,CFFAC,CLDKWT,CLMAX,CLPOW,CLQ,CLSMR,CMMOM,COSS, |
| 1787 | & COSTH,CSPEED,CTHRPW,CTMAX,DECPAR,DECWT,DISF,DKLTM,EBEAM1,EBEAM2, |
| 1788 | & EMLST,EMMAX,EMMIN,EMPOW,EMSCA,ENHANC,ENSOF,EPOLN,ETAMIX,EVWGT, |
| 1789 | & EXAG,F0MIX,F1MIX,F2MIX,GAMH,GAMMAX,GAMW,GAMWT,GAMZ,GAMZP,GCOEF, |
| 1790 | & GEV2NB,GEV2MM,GPOLN,H1MIX,HBAR,HARDST,OMEGA0,PBEAM1,PBEAM2,PDIQK, |
| 1791 | & PGSMX,PGSPL,PHEP,PHIMIX,PHIPAR,PHOMAS,PIFAC,PLTCUT,PPAR,PPOLN, |
| 1792 | & PRECO,PRSOF,PSPLT,PTINT,PTMAX,PTMIN,PTPOW,PTRMS,PXRMS,PWT,Q2MAX, |
| 1793 | & Q2MIN,Q2POW,Q2WWMN,Q2WWMX,QCDL3,QCDL5,QCDLAM,QDIQK,QEV,QFCH,QG, |
| 1794 | & QLIM,QSPAC,QV,QWT,REPWT,RESN,RHOHEP,RHOPAR,RLTIM,RMASS,RMIN, |
| 1795 | & RSPIN,SCABI,SINS,SNGWT,SWEIN,SWTEF,SUD,THMAX,TLOUT,TMTOP,TMNISR, |
| 1796 | & TQWT,VCKM,VFCH,VGCUT,VHEP,VMIN2,VPAR,VPCUT,VQCUT,VTXPIP,VTXQDK, |
| 1797 | & WBIGST,WGTMAX,WGTSUM,WHMIN,WSQSUM,XFACT,XLMIN,XMIX,XMRCT,XX, |
| 1798 | & XXMIN,YBMAX,YBMIN,YJMAX,YJMIN,YMIX,YMRCT,YWWMAX,YWWMIN,ZBINM, |
| 1799 | & ZJMAX,ZMXISR |
| 1800 | C |
| 1801 | INTEGER |
| 1802 | & CLDIR,IAPHIG,IBRN,IBSH,ICHRG,ICO,IDCMF,IDHEP,IDHW,IDK,IDKPRD,IDN, |
| 1803 | & IDPAR,IDPDG,IERROR,IFLAV,IFLMAX,IFLMIN,IHPRO,IMQDK,INHAD,INTER, |
| 1804 | & IOPDKL,IOPHIG,IOPREM,IPART1,IPART2,IPRINT,IPRO,IPROC,ISLENT, |
| 1805 | & ISPAC,ISTAT,ISTHEP,ISTPAR,JCOPAR,JDAHEP,JDAPAR,JMOHEP,JMOPAR, |
| 1806 | & JNHAD,LNEXT,LOCN,LOCQ,LRSUD,LSTRT,LWEVT,LWSUD,MAPQ,MAXER,MAXEV, |
| 1807 | & MAXFL,MAXPR,MODBOS,MODMAX,MODPDF,NBTRY,NCLDK,NCOLO,NCTRY,NDKYS, |
| 1808 | & NDTRY,NETRY,NEVHEP,NEVPAR,NFLAV,NGSPL,NHEP,NME,NMODES,NMXCDK, |
| 1809 | & NMXDKS,NMXHEP,NMXJET,NMXMOD,NMXPAR,NMXQDK,NMXRES,NMXSUD,NPAR, |
| 1810 | & NPRODS,NQDK,NQEV,NRES,NRN,NSPAC,NSTRU,NSTRY,NSUD,NUMER,NUMERU, |
| 1811 | & NWGTS,NZBIN,SUDORD |
| 1812 | C |
| 1813 | LOGICAL |
| 1814 | & AZSOFT,AZSPIN,BGSHAT,BREIT,CLRECO,COLISR,DKPSET,FROST,FSTEVT, |
| 1815 | & FSTWGT,GENEV,GENSOF,HARDME,HVFCEN,MAXDKL,MIXING,NOSPAC,NOWGT, |
| 1816 | & PRNDEC,PIPSMR,PRVTX,RSTAB,SOFTME,TMPAR,TPOL,USECMF,VTOCDK,VTORDK, |
| 1817 | & ZPRIME |
| 1818 | C |
| 1819 | CHARACTER*4 |
| 1820 | & BDECAY |
| 1821 | CHARACTER*8 |
| 1822 | & PART1,PART2,RNAME |
| 1823 | CHARACTER*20 |
| 1824 | & AUTPDF |
| 1825 | C |
| 1826 | C New standard event common |
| 1827 | PARAMETER (NMXHEP=2000) |
| 1828 | COMMON/HEPEVT/NEVHEP,NHEP,ISTHEP(NMXHEP),IDHEP(NMXHEP), |
| 1829 | & JMOHEP(2,NMXHEP),JDAHEP(2,NMXHEP),PHEP(5,NMXHEP),VHEP(4,NMXHEP) |
| 1830 | C |
| 1831 | C Beams, process and number of events |
| 1832 | COMMON/HWBEAM/IPART1,IPART2 |
| 1833 | COMMON/HWBMCH/PART1,PART2 |
| 1834 | COMMON/HWPROC/EBEAM1,EBEAM2,PBEAM1,PBEAM2,IPROC,MAXEV |
| 1835 | C |
| 1836 | C Basic parameters (and quantities derived from them) |
| 1837 | COMMON/HWPRAM/AFCH(16,2),ALPHEM,B1LIM,BETAF,BTCLM,CAFAC,CFFAC, |
| 1838 | & CLMAX,CLPOW,CLSMR,CSPEED,ENSOF,ETAMIX,F0MIX,F1MIX,F2MIX,GAMH, |
| 1839 | & GAMW,GAMZ,GAMZP,GEV2NB,H1MIX,PDIQK,PGSMX,PGSPL(4),PHIMIX,PIFAC, |
| 1840 | & PRSOF,PSPLT,PTRMS,PXRMS,QCDL3,QCDL5,QCDLAM,QDIQK,QFCH(16),QG, |
| 1841 | & QSPAC,QV,SCABI,SWEIN,TMTOP,VFCH(16,2),VCKM(3,3),VGCUT,VQCUT, |
| 1842 | & VPCUT,ZBINM,IOPREM,IPRINT,ISPAC,LRSUD,LWSUD,MODPDF(2),NBTRY, |
| 1843 | & NCOLO,NCTRY,NDTRY,NETRY,NFLAV,NGSPL,NSTRU,NSTRY,NZBIN,AZSOFT, |
| 1844 | & AZSPIN,CLDIR,HARDME,NOSPAC,PRNDEC,PRVTX,SOFTME,ZPRIME |
| 1845 | C |
| 1846 | COMMON/HWPRCH/AUTPDF(2),BDECAY |
| 1847 | C |
| 1848 | C Parton shower common (same format as /HEPEVT/) |
| 1849 | PARAMETER (NMXPAR=500) |
| 1850 | COMMON/HWPART/NEVPAR,NPAR,ISTPAR(NMXPAR),IDPAR(NMXPAR), |
| 1851 | & JMOPAR(2,NMXPAR),JDAPAR(2,NMXPAR),PPAR(5,NMXPAR),VPAR(4,NMXPAR) |
| 1852 | C |
| 1853 | C Parton polarization common |
| 1854 | COMMON/HWPARP/DECPAR(2,NMXPAR),PHIPAR(2,NMXPAR),RHOPAR(2,NMXPAR), |
| 1855 | & TMPAR(NMXPAR) |
| 1856 | C |
| 1857 | C Electroweak boson common |
| 1858 | PARAMETER (MODMAX=5) |
| 1859 | COMMON/HWBOSC/ALPFAC,BRHIG(12),ENHANC(12),GAMMAX,RHOHEP(3,NMXHEP), |
| 1860 | & IOPHIG,MODBOS(MODMAX) |
| 1861 | C |
| 1862 | C Parton colour common |
| 1863 | COMMON/HWPARC/JCOPAR(4,NMXPAR) |
| 1864 | C |
| 1865 | C other HERWIG branching, event and hard subprocess common blocks |
| 1866 | COMMON/HWBRCH/ANOMSC(2,2),HARDST,PTINT(3,2),XFACT,INHAD,JNHAD, |
| 1867 | & NSPAC(7),ISLENT,BREIT,FROST,USECMF |
| 1868 | C |
| 1869 | COMMON/HWEVNT/AVWGT,EVWGT,GAMWT,TLOUT,WBIGST,WGTMAX,WGTSUM,WSQSUM, |
| 1870 | & IDHW(NMXHEP),IERROR,ISTAT,LWEVT,MAXER,MAXPR,NOWGT,NRN(2),NUMER, |
| 1871 | & NUMERU,NWGTS,GENSOF |
| 1872 | C |
| 1873 | COMMON/HWHARD/ASFIXD,CLQ(7,6),COSS,COSTH,CTMAX,DISF(13,2),EMLST, |
| 1874 | & EMMAX,EMMIN,EMPOW,EMSCA,EPOLN(3),GCOEF(7),GPOLN,OMEGA0,PHOMAS, |
| 1875 | & PPOLN(3),PTMAX,PTMIN,PTPOW,Q2MAX,Q2MIN,Q2POW,Q2WWMN,Q2WWMX,QLIM, |
| 1876 | & SINS,THMAX,TMNISR,TQWT,XX(2),XLMIN,XXMIN,YBMAX,YBMIN,YJMAX, |
| 1877 | & YJMIN,YWWMAX,YWWMIN,WHMIN,ZJMAX,ZMXISR,IAPHIG,IBRN(2),IBSH, |
| 1878 | & ICO(10),IDCMF,IDN(10),IFLMAX,IFLMIN,IHPRO,IPRO,MAPQ(6),MAXFL, |
| 1879 | & BGSHAT,COLISR,FSTEVT,FSTWGT,GENEV,HVFCEN,TPOL |
| 1880 | C |
| 1881 | C Arrays for particle properties (NMXRES = max no of particles defined) |
| 1882 | PARAMETER(NMXRES=400) |
| 1883 | COMMON/HWPROP/RLTIM(0:NMXRES),RMASS(0:NMXRES),RSPIN(0:NMXRES), |
| 1884 | & ICHRG(0:NMXRES),IDPDG(0:NMXRES),IFLAV(0:NMXRES),NRES, |
| 1885 | & VTOCDK(0:NMXRES),VTORDK(0:NMXRES) |
| 1886 | C |
| 1887 | COMMON/HWUNAM/RNAME(0:NMXRES) |
| 1888 | C |
| 1889 | C Arrays for particle decays (NMXDKS = max total no of decays, |
| 1890 | C NMXMOD = max no of modes for a particle) |
| 1891 | PARAMETER(NMXDKS=4000,NMXMOD=200) |
| 1892 | COMMON/HWUPDT/BRFRAC(NMXDKS),CMMOM(NMXDKS),DKLTM(NMXRES), |
| 1893 | & IDK(NMXDKS),IDKPRD(5,NMXDKS),LNEXT(NMXDKS),LSTRT(NMXRES),NDKYS, |
| 1894 | & NME(NMXDKS),NMODES(NMXRES),NPRODS(NMXDKS),DKPSET,RSTAB(0:NMXRES) |
| 1895 | C |
| 1896 | C Weights used in cluster decays |
| 1897 | COMMON/HWUWTS/REPWT(0:3,0:4,0:4),SNGWT,DECWT,QWT(3),PWT(12), |
| 1898 | & SWTEF(NMXRES) |
| 1899 | C |
| 1900 | C Parameters for cluster decays (NMXCDK = max total no of cluster |
| 1901 | C decay channels) |
| 1902 | PARAMETER(NMXCDK=4000) |
| 1903 | COMMON/HWUCLU/CLDKWT(NMXCDK),CTHRPW(12,12),PRECO,RESN(12,12), |
| 1904 | & RMIN(12,12),LOCN(12,12),NCLDK(NMXCDK),CLRECO |
| 1905 | C |
| 1906 | C Variables controling mixing and vertex information |
| 1907 | COMMON/HWDIST/EXAG,GEV2MM,HBAR,PLTCUT,VMIN2,VTXPIP(4),XMIX(2), |
| 1908 | & XMRCT(2),YMIX(2),YMRCT(2),IOPDKL,MAXDKL,MIXING,PIPSMR |
| 1909 | C |
| 1910 | C Arrays for temporarily storing heavy-b,c-hadrons decaying partonicaly |
| 1911 | C (NMXBDK = max no such b-hadron decays in an event) |
| 1912 | PARAMETER (NMXQDK=20) |
| 1913 | COMMON/HWQDKS/VTXQDK(4,NMXQDK),IMQDK(NMXQDK),LOCQ(NMXQDK),NQDK |
| 1914 | C |
| 1915 | C Parameters for Sudakov form factors |
| 1916 | C (NMXSUD= max no of entries in lookup table) |
| 1917 | PARAMETER (NMXSUD=1024) |
| 1918 | COMMON/HWUSUD/ACCUR,QEV(NMXSUD,6),SUD(NMXSUD,6),INTER,NQEV,NSUD, |
| 1919 | & SUDORD |
| 1920 | C |
| 1921 | PARAMETER (NMXJET=200) |
| 1922 | ------------------------------------------------------------------------ |
| 1923 | |
| 1924 | ****** 8. FORM FACTOR FILE ****** |
| 1925 | |
| 1926 | HERWIG uses look-up tables of Sudakov form factors for the evolution |
| 1927 | of initial- and final-state parton showers. These can be read from |
| 1928 | an input file rather than being recomputed each time. The reading, |
| 1929 | writing and computing of form factor tables is controlled by integer |
| 1930 | parameters LRSUD and LWSUD: |
| 1931 | |
| 1932 | LRSUD = N>0 Read form factors for this run from unit N |
| 1933 | LRSUD = 0 Compute new form factor tables for this run |
| 1934 | LRSUD < 0 Form factor tables are already loaded |
| 1935 | LWSUD = N>0 Write form factors on unit N for future use |
| 1936 | LWSUD = 0 Do not write new form factor tables |
| 1937 | |
| 1938 | The option LRSUD<0 allows the program to be initialized several times |
| 1939 | in the same run (e.g. to generate various event types) without recom- |
| 1940 | puting or rereading form factors. |
| 1941 | |
| 1942 | N.B. The Sudakov form factors depend on the parameters QCDLAM, VQCUT, |
| 1943 | VGCUT, NCOLO, NFLAV, NAFLA, RMASS(13) and RMASS(i) for i=1,...,NFLAV. |
| 1944 | Consequently form factor tables MUST be recomputed every time any of |
| 1945 | these parameters is changed. From version 5.1 onwards, these |
| 1946 | parameters are written/read with the form factor tables and checks |
| 1947 | are performed to ensure consistency. |
| 1948 | |
| 1949 | The parton showering algorithm uses the two-loop alpha_s, with |
| 1950 | matching at each flavour threshold. However, the Sudakov table can be |
| 1951 | computed with either the one-loop or two-loop form, according to the |
| 1952 | variable SUDORD (= 1 or 2 respectively, DEFAULT=1). If SUDORD=1 the |
| 1953 | two-loop value is recovered using the veto algorithm in the shower, |
| 1954 | whereas if SUDORD=2 no vetoes are used in the final-state evolution. |
| 1955 | This means that the relative weight of any shower configuration can |
| 1956 | be calculated in a closed form, hence that showers can be `forced'. |
| 1957 | |
| 1958 | To next-to-leading order the two possibilities should be identical, |
| 1959 | but they differ at beyond-NLO, so some results may change a little. |
| 1960 | The most noticeable difference is that the form factor table takes a |
| 1961 | factor of about five times longer to compute with SUDORD=2 than 1. |
| 1962 | ------------------------------------------------------------------------ |
| 1963 | |
| 1964 | ****** 9. EVENT DATA ****** |
| 1965 | |
| 1966 | /HEPEVT/ is the standard common block containing current event data: |
| 1967 | |
| 1968 | NEVHEP - event number |
| 1969 | NHEP - number of entries for this event |
| 1970 | ISTHEP(I) - status of entry I (see below) |
| 1971 | IDHEP(I) - identity of entry I (revised Particle Data Group code) |
| 1972 | JMOHEP(1,I) - pointer to first mother of entry I (see below) |
| 1973 | JMOHEP(2,I) - pointer to second mother of entry I (see below) |
| 1974 | JDAHEP(1,I) - pointer to first daughter of entry I (see below) |
| 1975 | JDAHEP(2,I) - pointer to last daughter of entry I (see below) |
| 1976 | PHEP(*,I) - (Px,Py,Pz,E,M) of entry I: M=sign(sqrt(abs(m**2)),m**2) |
| 1977 | VHEP(*,I) - (x,y,z,t) of prod'n vertex of entry I (see section 13) |
| 1978 | |
| 1979 | All momenta are given in the laboratory frame, in which the input |
| 1980 | beam momenta are PBEAM1 and PBEAM2 as specified by the user and point |
| 1981 | along the +z and -z directions respectively. Final state particles |
| 1982 | have ISTHEP(I) = 1. See the next section for a complete list of the |
| 1983 | special status codes used by HERWIG. |
| 1984 | |
| 1985 | The identity codes IDHEP are as those suggested by the LEP II Working |
| 1986 | group i.e. the revised Particle Data Group numbers plus the following |
| 1987 | |
| 1988 | * IDHEP = 91 for clusters, 94 for jets, 0 for others with no PDG code. |
| 1989 | |
| 1990 | (HERWIG also has its own internal identity codes IDHW(I), stored in |
| 1991 | /HWEVNT/. The utility subroutine HWUIDT translates between HERWIG and |
| 1992 | PDG identity codes. See section 20 for further details.) |
| 1993 | |
| 1994 | The mother/daughter pointers are standard, except that JMOHEP(2,I) |
| 1995 | and JDAHEP(2,I) for a PARTON are its COLOUR mother and daughter, |
| 1996 | i.e., the partons to which its colour and anticolour are connected, |
| 1997 | respectively. For this purpose the primary partons from a hard sub- |
| 1998 | process are all regarded as outgoing (see examples in sects. 15, 19 |
| 1999 | and 21). Since quarks have no anticolour, JDAHEP(2,I) is used to |
| 2000 | point to its FLAVOUR partner. Similarly for JMOHEP(2,I) in the case |
| 2001 | of an antiquark. |
| 2002 | |
| 2003 | In addition to entries representing partons, particles, clusters etc, |
| 2004 | /HEPEVT/ contains purely informational entries representing the total |
| 2005 | c.m. momentum, hard and soft subprocess momenta, etc. See section 10 |
| 2006 | for the corresponding status codes. |
| 2007 | |
| 2008 | Information from all stages of event processing is retained in |
| 2009 | /HEPEVT/ so the same particle may appear several times with different |
| 2010 | status codes. For example, an outgoing parton from a hard scattering |
| 2011 | (entered initially with status 113 or 114) will appear after process- |
| 2012 | ing as an on-mass-shell parton before QCD branching (status 123,124), |
| 2013 | an off-mass-shell entry representing the flavour and momentum of the |
| 2014 | outgoing jet (status 143,144), and a jet constituent (157). It might |
| 2015 | also appear again in other contexts, e.g. as a spectator in a heavy |
| 2016 | flavour decay (status 154,160). |
| 2017 | |
| 2018 | Incoming partons (entered with status 111, 112, changed to 121, 122 |
| 2019 | after branching) give rise to spacelike jets (status 141,142, m**2<0, |
| 2020 | indicated by PHEP(5,IHEP)<0) due to the loss of momentum via initial |
| 2021 | state bremsstrahlung. The same applies in principle to incoming |
| 2022 | leptons, but QED radiative corrections are not yet included. |
| 2023 | |
| 2024 | Each parton jet begins with a status 141-144 jet entry giving the |
| 2025 | total flavour and momentum of the jet. The first mother pointer of |
| 2026 | this entry gives the location of the parent hard parton, while the |
| 2027 | second gives that of the subprocess c.m. momentum. If QCD branching |
| 2028 | has occurred, this is followed by a lightlike CONE entry, which |
| 2029 | fixes the angular extent of the jet and its azimuthal orientation |
| 2030 | relative to the parton with which it interferes. The interfering par- |
| 2031 | ton is listed as the second mother of the cone. Next come the actual |
| 2032 | constituents of the jet. If no branching has occurred, there is no |
| 2033 | cone and the single jet constituent is the same as the jet. |
| 2034 | ------------------------------------------------------------------------ |
| 2035 | |
| 2036 | ****** 10. STATUS CODES ****** |
| 2037 | |
| 2038 | A complete list of currently-used HERWIG status codes is given below. |
| 2039 | Many are used only in intermediate stages of event processing. The |
| 2040 | most important for users are probably 1 (final-state particle), 101-3 |
| 2041 | (initial state), 141-4 (jets), and 199 (decayed b- and t-flavoured |
| 2042 | hadrons). |
| 2043 | |
| 2044 | The event status ISTAT in common /HWEVNT/ is roughly ISTHEP-100 where |
| 2045 | ISTHEP is the status of entries being processed. However, ISTAT=100 |
| 2046 | for completed events. |
| 2047 | |
| 2048 | +------+-------------------------------------------+ |
| 2049 | |ISTHEP| Description | |
| 2050 | +------+-------------------------------------------+ |
| 2051 | | 1 | final state particle | |
| 2052 | | 2 | parton before hadronization | |
| 2053 | | 3 | documentation line | |
| 2054 | +------+-------------------------------------------+ |
| 2055 | | 100 | cone limiting jet evolution | |
| 2056 | | 101 | `beam' (beam 1) | |
| 2057 | | 102 | `target' (beam 2) | |
| 2058 | | 103 | overall centre of mass | |
| 2059 | +------+-------------------------------------------+ |
| 2060 | | 110 | unprocessed hard process CoM | |
| 2061 | | 111 | " beam parton | |
| 2062 | | 112 | " target " | |
| 2063 | | 113 | " outgoing " 3 | |
| 2064 | | 114 | " outgoing " 4 | |
| 2065 | | 115 | " spectator " | |
| 2066 | +------+-------------------------------------------+ |
| 2067 | |120-25| as 110-15, after processing | |
| 2068 | +------+-------------------------------------------+ |
| 2069 | | 130 | lepton in jet (unboosted) | |
| 2070 | |131-34| as 141-44, unboosted to CoM | |
| 2071 | | 135 | spacelike parton (beam, unboosted) | |
| 2072 | | 136 | " " (target, " ) | |
| 2073 | | 137 | spectator (beam, unboosted) | |
| 2074 | | 138 | " (target, " ) | |
| 2075 | | 139 | parton from branching (unboosted) | |
| 2076 | | 140 | " " g splitting ( " ) | |
| 2077 | +------+-------------------------------------------+ |
| 2078 | |141-44| jet from parton type 111-14 | |
| 2079 | |145-50| as 135-40 boosted, unclustered | |
| 2080 | +------+-------------------------------------------+ |
| 2081 | | 151 | as 159, not yet clustered | |
| 2082 | | 152 | as 160, " " " | |
| 2083 | | 153 | spectator from beam | |
| 2084 | | 154 | " " target | |
| 2085 | | 155 | heavy quark before decay | |
| 2086 | | 156 | spectator before heavy decay | |
| 2087 | | 157 | parton from QCD branching | |
| 2088 | | 158 | " after gluon splitting | |
| 2089 | | 159 | " from cluster splitting | |
| 2090 | | 160 | spectator after heavy decay | |
| 2091 | +------+-------------------------------------------+ |
| 2092 | | 161 | beam spectator after gluon splitting | |
| 2093 | | 162 | target " " " " | |
| 2094 | | 163 | other cluster before soft process | |
| 2095 | | 164 | beam " " " " | |
| 2096 | | 165 | target " " " " | |
| 2097 | | 167 | unhadronized beam cluster | |
| 2098 | | 168 | unhadronized target cluster | |
| 2099 | +------+-------------------------------------------+ |
| 2100 | | 170 | soft process centre of mass | |
| 2101 | | 171 | soft cluster (beam, unhadronized) | |
| 2102 | | 172 | soft cluster (target, " ) | |
| 2103 | | 173 | soft cluster (other, " ) | |
| 2104 | +------+-------------------------------------------+ |
| 2105 | | 181 | beam cluster (no soft process) | |
| 2106 | | 182 | target " ( " " " ) | |
| 2107 | | 183 | hard process " (hadronized) | |
| 2108 | | 184 | soft " (beam, hadronized) | |
| 2109 | | 185 | " " (target, " ) | |
| 2110 | | 186 | " " (other, " ) | |
| 2111 | +------+-------------------------------------------+ |
| 2112 | |190-93| as 195-98, before decays | |
| 2113 | | 195 | direct unstable non-hadron | |
| 2114 | | 196 | " " hadron (1-body cluster) | |
| 2115 | | 197 | " " " (2-body cluster) | |
| 2116 | | 198 | indirect unstable hadron or lepton | |
| 2117 | | 199 | decayed heavy flavour hadron | |
| 2118 | +------+-------------------------------------------+ |
| 2119 | | 200 | neutral B meson, flavour at production | |
| 2120 | +------+-------------------------------------------+ |
| 2121 | ------------------------------------------------------------------------ |
| 2122 | |
| 2123 | ****** 11. EVENT WEIGHTS ****** |
| 2124 | |
| 2125 | The default is to generate unweighted events (EVWGT=AVWGT). Then |
| 2126 | event distributions are generated by computing a weight proportional |
| 2127 | to the cross section and comparing it with a random number times the |
| 2128 | maximum weight. Set WGTMAX to the maximum weight, or to zero for the |
| 2129 | program to compute it. If a weight greater than WGTMAX is generated |
| 2130 | during execution, a warning is printed and WGTMAX is reset. Similarly |
| 2131 | if the efficiency is too low (WGTMAX too large). If these errors |
| 2132 | occur too often, output event distributions could be distorted. |
| 2133 | |
| 2134 | To generate weighted events, set NOWGT=.FALSE. in common /HWEVNT/. |
| 2135 | |
| 2136 | In QCD hard scattering and heavy flavour and direct photon production |
| 2137 | (IPROC = 1500 to 1800) the transverse energy distribution of weighted |
| 2138 | events (or the efficiency for unweighted events) can be varied using |
| 2139 | the parameters PTMIN, PTMAX and PTPOW. |
| 2140 | |
| 2141 | Similarly in Drell-Yan processes (IPROC = 13**) the lepton pair mass |
| 2142 | distribution is controlled by the parameters EMMIN, EMMAX and EMPOW, |
| 2143 | and in deep inelastic scattering the Q**2 distribution is set by |
| 2144 | Q2MIN, Q2MAX and Q2POW. |
| 2145 | |
| 2146 | Data on weights generated are output at the end of the run. The mean |
| 2147 | weight is an estimate of the cross section (in nanobarns) integrated |
| 2148 | over the region used for event generation. |
| 2149 | |
| 2150 | N.B. The mean weight is the sum of weights divided by the total |
| 2151 | number of WEIGHTS generated, not the total number of EVENTS. |
| 2152 | ------------------------------------------------------------------------ |
| 2153 | |
| 2154 | ****** 12. HEAVY FLAVOUR DECAYS ****** |
| 2155 | |
| 2156 | Heavy quark decays are treated as secondary hard subprocesses. Top |
| 2157 | quarks can decay either before or after hadronization, depending on |
| 2158 | the value of the logical variable DECAY returned by the subroutine |
| 2159 | HWDTOP. At present decay occurs before hadronization (DECAY=.TRUE.) |
| 2160 | if the top mass is above 130 GeV (default=170 GeV). Any hypothetical |
| 2161 | heavier quarks always decay before hadronization. Top- and bottom- |
| 2162 | flavoured hadrons are split into collinear heavy quark and spectator |
| 2163 | and the former decays independently. After decay, parton showers may |
| 2164 | be generated from coloured decay products, in the usual way. See |
| 2165 | Nucl. Phys. B330 (1990) 261 for details of the treatment of colour |
| 2166 | coherence in these showers. |
| 2167 | |
| 2168 | The arrays FBTM, FTOP & FHVY which were used in versions before 5.9 |
| 2169 | to store the bottom, top & heavier quarks' partonic decay fractions |
| 2170 | are gone. Such decays are specified in the decay tables like other |
| 2171 | particles' decay modes: this permits different decays to be given to |
| 2172 | individual heavy hadrons. Changes to the decay table entries can be |
| 2173 | made on an event by event basis if desired. Partonic decays of charm |
| 2174 | hadrons and quarkonium states are also now supported. The products' |
| 2175 | order in a partonic decay mode is significant. For example, if the |
| 2176 | decay is Q --> W+q --> (f+fbar')+q occurring inside a Q-sbar hadron, |
| 2177 | the required ordering is: |
| 2178 | |
| 2179 | Q+sbar --->(f+fbar')+(q+sbar) |
| 2180 | or (q+fbar')+(f+sbar) `colour rearranged' |
| 2181 | |
| 2182 | In both cases the (V-A)^2 ME^2 is proportional to: p_0.p_2 * p_1*p_3 |
| 2183 | |
| 2184 | The structure of the program has been altered so that secondary hard |
| 2185 | subrocess and subsequent fragmentation associated with each partonic |
| 2186 | heavy hadron decay appear separately. Thus pre-hadronization t quark |
| 2187 | decays are treated individually as are any subsequent bottom hadron |
| 2188 | partonic decays. |
| 2189 | |
| 2190 | Additionally decays of heavy hadrons to exclusive non-partonic final |
| 2191 | states are supported. No check against double counting from partonic |
| 2192 | modes is included. However this isn't expected to be a major problem |
| 2193 | for the semi-leptonic and 2-body hadronic modes supplied. |
| 2194 | ------------------------------------------------------------------------ |
| 2195 | |
| 2196 | ****** 13. SPACE-TIME STRUCTURE OF EVENTS ****** |
| 2197 | |
| 2198 | The space-time structure of events is now available for all types of |
| 2199 | subprocess. The production vertex of each: parton, cluster, unstable |
| 2200 | resonance and final state particle is supplied in the VHEP(4,NMXHEP) |
| 2201 | array of /HEPEVT/; set PRVTX=.TRUE. to include this information when |
| 2202 | printing the event record (120 column format). The units are: x,y,z |
| 2203 | in mm and t mm/c. In the case of partons and clusters the production |
| 2204 | points are always given in a loacl coordinate system centered on the |
| 2205 | their hard sub-process. This helps seperate the fermi scale partonic |
| 2206 | showers from millimeter scale distances possible in particle decays, |
| 2207 | for example the partonic decays of heavy (c,b) hadrons. The vertices |
| 2208 | of hadrons produced in cluster decays are always corrected back into |
| 2209 | the laboratory coordinate system. |
| 2210 | |
| 2211 | It is possible to vary the principal interaction point, assigned to |
| 2212 | the CMF (ISTHEP=103) track, by setting PIPSMR=.TRUE. The smearing is |
| 2213 | generated by the routine HWRPIP according to a triple Gaussian, see |
| 2214 | the code for details. Also, it is possible to veto particle decays |
| 2215 | that would occur outside a specified volume by setting MAXDKL=.TRUE. |
| 2216 | Each putative decay is tested in HWDXLM and if it would have decayed |
| 2217 | outside the chosen volume it is frozen and labelled as final state. |
| 2218 | Using IOPDKL = 1,2 selects a cylindrical or spherical allowed region |
| 2219 | (about the origin) see the code for details. |
| 2220 | |
| 2221 | Lepton and hadron lifetimes are supplied in the array RLTIM(NMXRES). |
| 2222 | The lifetimes of heavy quarks (TQRK, VQRK, AQRK, HQRK AND HPQK), and |
| 2223 | weak bosons (W+, W-, Z0/GAMA*, HIGGS and Z0P) are derived from their |
| 2224 | calculated or specified widths as calculated in HWUDKS, whilst light |
| 2225 | quarks and gluons are given an effective minimum width, sqrt(VMIN2), |
| 2226 | that acts as a lifetime cut-off - see below. Recall that the proper |
| 2227 | lifetime = HBAR/Gamma. All particles whose lifetimes are larger than |
| 2228 | PLTCUT are set stable. |
| 2229 | |
| 2230 | The proper (= rest frame) time at which an unstable lepton or hadron |
| 2231 | decays is generated according to the exponential decay law with mean |
| 2232 | lifetime <tau>=RLTIM. The laboratory frame decay time and distance |
| 2233 | travelled are obtained by applying a boost: |
| 2234 | |
| 2235 | Rest Prob (proper time < t) = 1 * exp(-t/<tau>) |
| 2236 | frame <tau> |
| 2237 | |
| 2238 | Lab. time = gamma * proper time beta = v/c |
| 2239 | frame dist = beta * gamma * proper time gamma = 1/sqrt(1-beta^2) |
| 2240 | |
| 2241 | The production vertices of the daughter particles are calculated by |
| 2242 | adding the distance travelled by the mother particle as given above |
| 2243 | to its production vertex. A similar prescription is used for parton |
| 2244 | showers: proper lifetimes are taken from an exponential distribution |
| 2245 | with a virtuality dependent mean lifetime 1/HBAR*sqrt(q^2/(q^2-m^2)) |
| 2246 | inspired by the uncertainty relationship: mean lifetimes are limited |
| 2247 | by a cut-off on the minimum virtuality VMIN2. The mean lifetimes of |
| 2248 | heavy quarks and weak bosons, which can have appreciable widths, are |
| 2249 | given by: |
| 2250 | |
| 2251 | hbar.sqrt(q^2) |
| 2252 | <tau>(q^2) = ----------------------------- |
| 2253 | \/(q^2-M^2)^2 + (Gamma.q^2/M)^2 |
| 2254 | |
| 2255 | As this formula has the appropriate limits for vanishing virtuality, |
| 2256 | q^2=m^2, or width, gamma=0, it is actually also used in the hadronic |
| 2257 | and partonic showers: see HWUDKL. |
| 2258 | |
| 2259 | In the case of cluster the initial production vertex is taken as the |
| 2260 | midpoint of a line perpendicular to the cluster's direction and with |
| 2261 | pair. If such a cluster undergoes a forced splitting to two clusters |
| 2262 | the string picture is adopted. The vertex of the light quark pair is |
| 2263 | positioned so that the masses of the two daughter clusters would be |
| 2264 | the same as that for two equivalent string fragments. The production |
| 2265 | vertices of the daughter clusters are given by the first crossing of |
| 2266 | their constituent q-qbar pairs. This part of the space-time picture |
| 2267 | is admittedly ad hoc however no physics depends upon it. |
| 2268 | |
| 2269 | When MIXING=.TRUE. particle - antiparticle mixing for B^0_d,s mesons |
| 2270 | is implimented. The probability that a meson is mixed when it decays |
| 2271 | is given in terms of its lab-frame decay time by: |
| 2272 | |
| 2273 | 1 sin(X*m*t/c<tau>E) X=Delta-M Y=Delta-Gamma |
| 2274 | Prob(mix) = - + ---------------------- ------- ----------- |
| 2275 | 2 2 *cosh(Y*m*t/c<tau>E) Gamma 2 * Gamma |
| 2276 | |
| 2277 | The ratios X and Y are stored in XMIX(I) & YMIX(I), I=1,2 for q=s,d. |
| 2278 | Whenever a neutral B meson occurs in an event a copy of the original |
| 2279 | track is always added to the event record, with ISTHEP=200, it gives |
| 2280 | the particle's flavour at the production (cluster decay) time. This |
| 2281 | is in addition to the usual decaying particle, ISTHEP=19*, track. |
| 2282 | ------------------------------------------------------------------------ |
| 2283 | |
| 2284 | ****** 14. COLOUR REARRANGEMENT MODEL ****** |
| 2285 | |
| 2286 | HERWIG now contains a colour rearrangement model based on the space- |
| 2287 | time structure of an event occuring at the end of the parton shower. |
| 2288 | This is illustrated in the simple example shown below where a colour |
| 2289 | neutral source results in a q-g-g-qbar shower. In the conventional |
| 2290 | hadronization model after a nonperturbative splitting of final state |
| 2291 | gluons - Wolfram ansatze - colour singlet clusters are formed from |
| 2292 | neighbouring q-qbar pairs: (ij)(pq)(kl). However when CLRECO=.TRUE. |
| 2293 | the program first creates colour singlet clusters as normal but then |
| 2294 | checks all (non-neighbouring) pairs of clusters to test if a colour |
| 2295 | rearrangement lowers the sum of the clusters' spatial sizes added in |
| 2296 | quadrature. A cluster's size is defined to be the Lorentz invariant, |
| 2297 | space-time distance between the constituent quark's and anitquark's |
| 2298 | production points. If an allowed alternative is found, that is: |
| 2299 | |
| 2300 | (ij)(kl) --> (il)(jk) s.t. (|d_ij|^2+|d_kl|^2) > (|d_il|^2+|d_kl|^2) |
| 2301 | |
| 2302 | then it is accepted with a probability given by PRECO (default 1/9). |
| 2303 | |
| 2304 | |
| 2305 | ____ i Normal: (ij) (pq) (kl) |
| 2306 | / |
| 2307 | /____/ j If: |
| 2308 | ------ |
| 2309 | / \ p |d_ij|^2+|d_kl|^2 > |d_il|^2+|d_kl|^2 |
| 2310 | ------| |
| 2311 | \______/ q colour rearr.: (il) (pq) (jk) |
| 2312 | ----- |
| 2313 | \ \ k Not allowed: (iq) (jp) (kl) |
| 2314 | \ ^ |
| 2315 | ---- l | colour octet |
| 2316 | |
| 2317 | Note that not all colour rearrangements are allowed, for instance in |
| 2318 | the example (ij)(pq) --> (ip)(jq) the cluster (jq) is a colour octet |
| 2319 | - it contains both products from a non-perturbative gluon splitting. |
| 2320 | |
| 2321 | Multiple colour rearrangements are considered by the program, as are |
| 2322 | those between clusters in jets arising from a single, colour neutral |
| 2323 | source - for example Z0 decay (as shown above) - or due to more than |
| 2324 | one source - for example e+e- --> W+W- --> 4 jets. In the later case |
| 2325 | a new parameter, EXAG, is available to artificially scale the W - or |
| 2326 | other weak boson - lifetimes so that any dependence of rearrangement |
| 2327 | effects on source separation can be investigated. The CLRECO option |
| 2328 | can be used for all the processes available in HERWIG. |
| 2329 | |
| 2330 | ** NOTE ** Before using the program with CLRECO=.TRUE. for detailed |
| 2331 | physics analyses the default parameters should be retuned to `lower |
| 2332 | energy' data with this option switched on. |
| 2333 | ------------------------------------------------------------------------ |
| 2334 | |
| 2335 | ****** 15. QCD HARD SUBPROCESSES ****** |
| 2336 | |
| 2337 | At present only 2->2 subprocesses are implemented. They are class- |
| 2338 | ified as shown below. |
| 2339 | |
| 2340 | +-----+------------------------------+---------+ |
| 2341 | |IHPRO| Process 1 + 2 -> 3 + 4 |Col/F.Con| |
| 2342 | +-----+------------------------------+---------+ |
| 2343 | | 1 | q + q -> q + q | 3 4 2 1 | |
| 2344 | | 2 | q + q -> q + q | 4 3 1 2 | |
| 2345 | | 3 | q + q' -> q + q' | 3 4 2 1 | |
| 2346 | | 4 | q + qbar -> q'+ qbar' | 2 4 1 3 | |
| 2347 | | 5 | q + qbar -> q + qbar | 3 1 4 2 | |
| 2348 | | 6 | q + qbar -> q + qbar | 2 4 1 3 | |
| 2349 | | 7 | q + qbar -> g + g | 2 4 1 3 | |
| 2350 | | 8 | q + qbar -> g + g | 2 3 4 1 | |
| 2351 | | 9 | q + qbar' -> q + qbar' | 3 1 4 2 | |
| 2352 | | 10 | q + g -> q + g | 3 1 4 2 | |
| 2353 | | 11 | q + g -> q + g | 3 4 2 1 | |
| 2354 | | 12 | qbar + q -> qbar' +q' | 3 1 4 2 | |
| 2355 | | 13 | qbar + q -> qbar + q | 2 4 1 3 | |
| 2356 | | 14 | qbar + q -> qbar + q | 3 1 4 2 | |
| 2357 | | 15 | qbar + q -> g + g | 3 1 4 2 | |
| 2358 | | 16 | qbar + q -> g + g | 4 1 2 3 | |
| 2359 | | 17 | qbar + q' -> qbar + q' | 2 4 1 3 | |
| 2360 | | 18 | qbar + qbar -> qbar + qbar | 4 3 1 2 | |
| 2361 | | 19 | qbar + qbar -> qbar + qbar | 3 4 2 1 | |
| 2362 | | 20 | qbar + qbar' -> qbar + qbar' | 4 3 1 2 | |
| 2363 | | 21 | qbar + g -> qbar + g | 2 4 1 3 | |
| 2364 | | 22 | qbar + g -> qbar + g | 4 3 1 2 | |
| 2365 | | 23 | g + q -> g + q | 2 4 1 3 | |
| 2366 | | 24 | g + q -> g + q | 3 4 2 1 | |
| 2367 | | 25 | g + qbar -> g + qbar | 3 1 4 2 | |
| 2368 | | 26 | g + qbar -> g + qbar | 4 3 1 2 | |
| 2369 | | 27 | g + g -> q + qbar | 2 4 1 3 | |
| 2370 | | 28 | g + g -> q + qbar | 4 1 2 3 | |
| 2371 | | 29 | g + g -> g + g | 4 1 2 3 | |
| 2372 | | 30 | g + g -> g + g | 4 3 1 2 | |
| 2373 | | 31 | g + g -> g + g | 2 4 1 3 | |
| 2374 | +-----+------------------------------+---------+ |
| 2375 | |
| 2376 | `Col/F.Con' refers to the colour/flavour connections between the |
| 2377 | partons:`I J K L' means that the colour of parton 1 comes from parton |
| 2378 | I, that of 2 from J, etc. For antiquarks, which have no colour (only |
| 2379 | anticolour), the label shows instead to which parton the flavour is |
| 2380 | connected. For this colour/flavour labelling all partons are defined |
| 2381 | as outgoing. Thus, for example, process 10 has colour connections |
| 2382 | 3 1 4 2, corresponding to the colour flow diagram: |
| 2383 | |
| 2384 | 1 -->--+ +-->-- 3 |
| 2385 | | | |
| 2386 | | | |
| 2387 | --<--+ +--<-- |
| 2388 | 2 -->------->-- 4 |
| 2389 | |
| 2390 | When different colour flows are possible, they are listed as separate |
| 2391 | subprocesses. This separation is not exact but is normally a good |
| 2392 | approximation. The sum of the colour flows is the exact lowest-order |
| 2393 | cross section. |
| 2394 | ------------------------------------------------------------------------ |
| 2395 | |
| 2396 | ****** 16. QCD DIRECT PHOTON SUBPROCESSES ****** |
| 2397 | |
| 2398 | +-----+------------------------------+---------+ |
| 2399 | |IHPRO| Process 1 + 2 -> 3 + 4 |Col/F.Con| |
| 2400 | +-----+------------------------------+---------+ |
| 2401 | | 41 | q + qbar -> g + photon | 2 3 1 4 | |
| 2402 | | 42 | q + gluon -> q + photon | 3 1 2 4 | |
| 2403 | | 43 | qbar + q -> g + photon | 3 1 2 4 | |
| 2404 | | 44 | qbar + gluon -> qbar + photon| 2 3 1 4 | |
| 2405 | | 45 | gluon + q -> q + photon| 2 3 1 4 | |
| 2406 | | 46 | gluon + qbar -> qbar + photon| 3 1 2 4 | |
| 2407 | | 47 | gluon + gluon-> gluon+ photon| 2 3 1 4 | |
| 2408 | +-----+------------------------------+---------+ |
| 2409 | | 51 | photon+ q -> gluon+ q | 1 4 2 3 | |
| 2410 | | 52 | photon+ qbar -> gluon+ qbar | 1 3 4 2 | |
| 2411 | | 53 | photon+ gluon-> q + qbar | 1 4 2 3 | |
| 2412 | +-----+------------------------------+---------+ |
| 2413 | | 61 | q + qbar -> photon+photon| 2 1 3 4 | |
| 2414 | | 62 | qbar + q -> photon+photon| 2 1 3 4 | |
| 2415 | | 63 | gluon + gluon-> photon+photon| 2 1 3 4 | |
| 2416 | +-----+------------------------------+---------+ |
| 2417 | | 71 | photon+ q -> M(S=0) +q' | 1 4 3 2 | |
| 2418 | | 72 | photon+ q -> M(S=1)L+q' | 1 4 3 2 | |
| 2419 | | 73 | photon+ q -> M(S=1)T+q' | 1 4 3 2 | |
| 2420 | | 74 | photon+ qbar -> M(S=0) +qbar'| 1 4 3 2 | |
| 2421 | | 75 | photon+ qbar -> M(S=1)L+qbar'| 1 4 3 2 | |
| 2422 | | 76 | photon+ qbar -> M(S=1)T+qbar'| 1 4 3 2 | |
| 2423 | +-----+------------------------------+---------+ |
| 2424 | |
| 2425 | N.B. The photon is connected to itself. |
| 2426 | ------------------------------------------------------------------------ |
| 2427 | |
| 2428 | ****** 17. QCD HIGGS PLUS JET SUBPROCESSES ****** |
| 2429 | |
| 2430 | +-----+------------------------------+---------+ |
| 2431 | |IHPRO| Process 1 + 2 -> 3 + 4 |Col/F.Con| |
| 2432 | +-----+------------------------------+---------+ |
| 2433 | | 81 | q + qbar -> g + H | 2 3 1 4 | |
| 2434 | | 82 | q + g -> q + H | 3 1 2 4 | |
| 2435 | | 83 | qbar + q -> g + H | 3 1 2 4 | |
| 2436 | | 84 | qbar + g -> qbar + H | 2 3 1 4 | |
| 2437 | | 85 | g + q -> q + H | 2 3 1 4 | |
| 2438 | | 86 | g + qbar -> qbar + H | 3 1 2 4 | |
| 2439 | | 87 | g + g -> g + H | 2 3 1 4 | |
| 2440 | +-----+------------------------------+---------+ |
| 2441 | |
| 2442 | N.B. The Higgs is connected to itself. |
| 2443 | ------------------------------------------------------------------------ |
| 2444 | |
| 2445 | ****** 18. ELECTROWEAK SUBPROCESSES ****** |
| 2446 | |
| 2447 | HERWIG generates Higgs bosons through gluon-gluon/quark-antiquark |
| 2448 | fusion, and W fusion in hadron-hadron collisions (IPROC=1600+ID and |
| 2449 | 1900+ID), in lepton-lepton collisions through the Bjorken process |
| 2450 | (that is, Z(*)->Z(*)H with one or both Zs off-shell) and W fusion |
| 2451 | (IPROC=300+ID and 400+ID), and in lepton-hadron collisions through W |
| 2452 | fusion (IPROC=9500+ID). Each process is generated according to the |
| 2453 | exact leading order matrix element in the s-channel approximation. |
| 2454 | This results in unitarity violation for Mh >> Mw, s >~ a few Mh^2, |
| 2455 | (where s=qh^2), so to regularize this, the Mh*GAMH in the propagator |
| 2456 | can be replaced by SQRT(s)*GAMH(s). The variable IOPHIG controls this |
| 2457 | procedure: |
| 2458 | |
| 2459 | +------+------------------------------+-----------+ |
| 2460 | |IOPHIG| Choose s according to | Reweight? | |
| 2461 | +------+------------------------------+-----------+ |
| 2462 | | 0 | s^2 / ((s-Mh^2)^2 + Mh*GAMH) | YES | |
| 2463 | | 1 | 1 / ((s-Mh^2)^2 + Mh*GAMH) | YES | |
| 2464 | | 2 | s^2 / ((s-Mh^2)^2 + Mh*GAMH) | NO | |
| 2465 | | 3 | 1 / ((s-Mh^2)^2 + Mh*GAMH) | NO | |
| 2466 | +------+------------------------------+-----------+ |
| 2467 | |
| 2468 | Where reweighting means weighting the distribution back to |
| 2469 | |
| 2470 | SQRT(s) * GAMH(s) |
| 2471 | ---------------------------- |
| 2472 | (s-Mh^2)^2 + SQRT(s)*GAMH(s) |
| 2473 | |
| 2474 | The default is IOPHIG=1. The difference between options 0 and 1 is |
| 2475 | purely in the weight distribution produced. Options 2 and 3 are |
| 2476 | intended primarily for users who wish to supply their own unitarity |
| 2477 | conserving reweighting function at the point indicated in routine |
| 2478 | HWHIGM. In all cases, the distribution is restricted to the range |
| 2479 | [Mh-GAMMAX*GAMH , Mh+GAMMAX*GAMH]. GAMMAX defaults to 10, but in the |
| 2480 | (probably unphysical) region Mh >~ 1TeV should be reduced to protect |
| 2481 | against poor weight distributions. These considerations do not affect |
| 2482 | the distribution noticably for Mh <~ 500 GeV, and GAMMAX can safely |
| 2483 | be increased if necessary. |
| 2484 | |
| 2485 | For each process, ID controls the Higgs decay: ID=1-6 for quarks, 7-9 |
| 2486 | for leptons, 10/11 for WW/ZZ pairs, and 12 for photons. In addition |
| 2487 | ID=0 gives quarks of all flavours, and ID=99 gives all decays. For |
| 2488 | each process, the average event weight is the cross section in nb |
| 2489 | times the branching fraction to the requested decay. The branching |
| 2490 | ratios to quarks use the next-to-leading logarithm corrections, those |
| 2491 | to WW/ZZ pairs allow for one or both bosons off-shell. The amplitudes |
| 2492 | for all Higgs vertices are multiplied by the factor ENHANC(ID) where |
| 2493 | ID is the same as in IPROC=300+ID except the gammagammaHiggs `vertex' |
| 2494 | which is calculated from ENHANC(6) and ENHANC(10) for the top and W |
| 2495 | loops. This allows the simulation of any chargeless scalar Higgs. |
| 2496 | Note however that pseudoscalar and charged Higgses, and processes |
| 2497 | involving more than one Higgs (eg the decay H-->hZ) are not included. |
| 2498 | |
| 2499 | Gauge bosons are generated through the processes of W + 1 parton |
| 2500 | production in hadron-hadron collisions, and WW pair production in |
| 2501 | lepton-lepton collisions, as well as in the Higgs processes mentioned |
| 2502 | above. In all cases their decay is controlled by the variable |
| 2503 | MODBOS(i). This controls the decay of the ith gauge boson per event: |
| 2504 | |
| 2505 | +---------+-----------------+-----------------+ |
| 2506 | |MODBOS(i)| W Decay | Z Decay | |
| 2507 | +---------+-----------------+-----------------+ |
| 2508 | | 0 | all | all | |
| 2509 | | 1 | qqbar | qqbar | |
| 2510 | | 2 | enu | e+e- | |
| 2511 | | 3 | munu | mu+mu- | |
| 2512 | | 4 | taunu | tau+tau- | |
| 2513 | | 5 | enu & munu | ee & mumu | |
| 2514 | | 6 | all | nunu | |
| 2515 | | 7 | all | bbbar | |
| 2516 | | >7 | all | all | |
| 2517 | +---------+-----------------+-----------------+ |
| 2518 | |
| 2519 | All entries of MODBOS default to 0. Bosons which are produced in |
| 2520 | pairs (ie. from WW pair production, or Higgs decay) are symmetrized |
| 2521 | in MODBOS(i) and MODBOS(i+1). For processes which directly produce |
| 2522 | gauge bosons, the event weight includes the branching fraction to the |
| 2523 | requested decay, but this is only true for Higgs production if decay |
| 2524 | to WW/ZZ is forced (ID=10/11) and not if ID=99. The spin-correlations |
| 2525 | in the decays are handled in one of two ways: |
| 2526 | (a) the diagonal members of the spin density matrix are stored in |
| 2527 | RHOHEP(i,IHEP), where i=1,2,3 for helicity=i-2 in the centre-of- |
| 2528 | mass frame of their production, for processes where this matrix |
| 2529 | is diagonal (ie. there is no interference between spin states). |
| 2530 | (b) the correlations in the decay are handled directly by the |
| 2531 | production routine where (a) is not possible. |
| 2532 | In the case of gamma gamma --> W W the decay correlations are not |
| 2533 | correctly included: they currently decay isotropically. |
| 2534 | |
| 2535 | The electroweak vector boson--fermion coupling constants are stored |
| 2536 | in the arrays QFCH(I), VFCH(I,J) and AFCH(I,J) for the charge, vector |
| 2537 | and axial vector couplings to the neutral current respectively. These |
| 2538 | are given in the convention |
| 2539 | V_f=(T_3/2-Qsin^2_W)/(cos_W sin_W); A_f=T_3/(2 cos_W sin_W). |
| 2540 | In each case, |
| 2541 | I= 1- 6: d,u,s,c,b,t (quarks) |
| 2542 | =11-16: e,nu_e,mu,nu_mu,tau,nu_tau (leptons) (`I=IDHW-110') |
| 2543 | J=1 for minimal SM: |
| 2544 | =2 for Z' couplings (only included if ZPRIME=.TRUE.) |
| 2545 | Note that no universality is assumed -- couplings can be arbitrarily |
| 2546 | set for each fermion species separately. |
| 2547 | The quark mixing matrix is stored in VCKM(K,L), K=1,2,3 for u,c,t, |
| 2548 | L=1,2,3 for d,s,b. |
| 2549 | |
| 2550 | A running electromagnetic coupling constant is provided, HWUAEM(Q2). |
| 2551 | ALPHEM =1/137 provides the normalisation at the Thomson (Q2=0) limit |
| 2552 | and is used for all processes involving real photons. |
| 2553 | The electroweak coupling is calculated as, |
| 2554 | g^2 = 4 PIFAC ALPHEM(Q2) / SWEIN, |
| 2555 | where Q2 is appropriate for the given process. |
| 2556 | Photon emission in parton showers, and in the `dead-zone' in e+e- |
| 2557 | is enhanced by a factor of ALPFAC (default=1.). |
| 2558 | ------------------------------------------------------------------------ |
| 2559 | |
| 2560 | ****** 19. INCLUDING NEW SUBPROCESSES ****** |
| 2561 | |
| 2562 | It should not be difficult for users to include further subprocesses |
| 2563 | in this version of the program if required. The parton and hard sub- |
| 2564 | process 4-momenta, masses and identity codes need to be entered in |
| 2565 | COMMON/HEPEVT/ with the appropriate status codes ISTHEP(I)=110-114 to |
| 2566 | tell the program which is which (see table in sect. 10). The colour/ |
| 2567 | flavour structure should be specified by the second mother and daugh- |
| 2568 | ter pointers as explained in section 9 (see also the sample output |
| 2569 | and guide, sections. 20 and 21). |
| 2570 | |
| 2571 | Apart from the status codes ISTHEP, the HERWIG identity codes IDHW(I) |
| 2572 | in COMMON/HWEVNT/ also need to be set correctly. The IDHW codes can |
| 2573 | be listed in a run with IPRINT=2: the most important are the quarks |
| 2574 | 1-6 (as IDHEP), antiquarks 7-12, gluon 13, overall c.m. 14, hard c.m. |
| 2575 | 15, soft c.m. 16, photon 59, leptons 121-126, antileptons 127-132. |
| 2576 | |
| 2577 | The utility subroutine HWUIDT(IOPT,IPDG,IHWG,NAME) is provided to |
| 2578 | translate between Particle Data Group code IPDG, HERWIG code IHWG, |
| 2579 | and HERWIG character*8 NAME, with IOPT=1,2,3 depending on which of |
| 2580 | IPDG, IHWG and NAME is the input argument. |
| 2581 | |
| 2582 | Consider for example the process of virtual photon-gluon fusion to |
| 2583 | make b+bbar in e p collisions. |
| 2584 | |
| 2585 | **** N.B. This process is now included as IPROC = 9102 **** |
| 2586 | |
| 2587 | We assume the user provides a subroutine to generate the momenta PHEP |
| 2588 | for the hard subprocess e+g -> e+b+bbar. The colour structure is |
| 2589 | |
| 2590 | (e)4 ........... 7(e) |
| 2591 | : |
| 2592 | : |
| 2593 | +-->-- 8(b) |
| 2594 | | |
| 2595 | -->--+ |
| 2596 | (g)5 --<-----<-- 9(bbar) |
| 2597 | |
| 2598 | Thus the momenta generated, together with those of the initial beams |
| 2599 | and the overall centre of mass, could be entered in the following |
| 2600 | sequence: |
| 2601 | |
| 2602 | +----+--------+------+-----+------+------+----+ |
| 2603 | |IHEP| Entry |ISTHEP|IDHEP|JMOHEP|JDAHEP|IDHW| |
| 2604 | +----+--------+------+-----+------+------+----+ |
| 2605 | | 1 | e beam | 101 | 11| 0 0| 0 0| 121| |
| 2606 | | 2 | p beam | 102 | 2212| 0 0| 0 0| 73| |
| 2607 | | 3 | ep c.m.| 103 | 0| 0 0| 0 0| 14| |
| 2608 | +----+--------+------+-----+------+------+----+ |
| 2609 | | 4 | e in | 111 | 11| 6 7| 0 7| 121| |
| 2610 | | 5 | gluon | 112 | 21| 6 9| 0 8| 13| |
| 2611 | | 6 | hard cm| 110 | 0| 4 5| 7 9| 15| |
| 2612 | | 7 | e out | 113 | 11| 6 4| 0 4| 121| |
| 2613 | | 8 | b | 114 | 5| 6 5| 0 9| 5| |
| 2614 | | 9 | bbar | 114 | -5| 6 8| 0 5| 11| |
| 2615 | +----+--------+------+-----+------+------+----+ |
| 2616 | |
| 2617 | Note that if there are more than two outgoing partons, the first has |
| 2618 | status 113 and all the others 114. Each parton has JMOHEP(1,I)=6 to |
| 2619 | indicate the location of the hard c.m. for this subprocess, while |
| 2620 | JMOHEP(2,I) gives the location of the colour mother (treating the in- |
| 2621 | coming gluon as outgoing) or the connected electron. JDAHEP(1,I) will |
| 2622 | be set by the jet generator HWBGEN, while JDAHEP(2,I) points to the |
| 2623 | anticolour mother (or connected electron). Finally the HERWIG identi- |
| 2624 | fiers IDHW(I) could be set to the indicated values by means of the |
| 2625 | translation subroutine HWUIDT as follows: |
| 2626 | |
| 2627 | CHARACTER*8 NAME |
| 2628 | ..... |
| 2629 | NHEP=9 |
| 2630 | IDHEP(1)=11 |
| 2631 | IDHEP(2)=2212 |
| 2632 | ..... |
| 2633 | IDHEP(9)=-5 |
| 2634 | DO 10 I=1,NHEP |
| 2635 | 10 CALL HWUIDT(1,IDHEP(I),IDHW(I),NAME) |
| 2636 | IDHW(6)=15 |
| 2637 | |
| 2638 | The last statement is needed because IDPDG(I)=0 returns IDHW(I)=14. |
| 2639 | If subroutine HWBGEN is now called, it will find the coloured partons |
| 2640 | and generate QCD jets from them. Subsequent calls to HWCFOR etc can |
| 2641 | then be used to form clusters and hadronize them. |
| 2642 | |
| 2643 | If the hard subprocess routine is called from HWEPRO, like those |
| 2644 | already provided, it should have two options controlled by the logic- |
| 2645 | al variable GENEV in COMMON/HWHARD/. For GENEV=.FALSE., an event |
| 2646 | weight (normally the cross section in nanobarns) is generated and |
| 2647 | stored as EVWGT in COMMON/HWEVNT/. If this weight is accepted by |
| 2648 | HWEPRO, the subroutine is called a second time with GENEV=.TRUE. and |
| 2649 | the corresponding event data should then be generated and stored as |
| 2650 | explained above. |
| 2651 | ------------------------------------------------------------------------ |
| 2652 | |
| 2653 | ****** 20. ERROR CONDITIONS ****** |
| 2654 | |
| 2655 | Certain combinations of input parameters may lead to problems in exe- |
| 2656 | cution. HERWIG tries to detect these and print a warning. Errors |
| 2657 | during execution are dealt with by HWWARN which prints the calling |
| 2658 | subprogram and a code and takes appropriate action. In general, the |
| 2659 | larger the code the more serious the problem. Refer to the source |
| 2660 | code to find out why HWWARN was called. Events can be rerun by |
| 2661 | setting the random number seeds NRN to the values given in the error |
| 2662 | message or event dump, and MAXWGT to the maximum weight encountered |
| 2663 | in the run. Contents of /HEPEVT/ can by printed by calling HWUEPR, |
| 2664 | those of /HWPART/ (last parton shower) by HWUBPR. |
| 2665 | |
| 2666 | If WGTMAX is increased during event generation, so that this message |
| 2667 | is printed: |
| 2668 | HWWARN CALLED FROM SUBPROGRAM HWEPRO: CODE = 1 |
| 2669 | EVENT 21: SEEDS = 836291635 & 1823648329 WEIGHT = 0.3893E-08 |
| 2670 | EVENT SURVIVES. EXECUTION CONTINUES |
| 2671 | NEW MAXIMUM WEIGHT = 0.428217360829367E-08 |
| 2672 | then to regenerate any later events, WGTMAX must be set to the printed |
| 2673 | value, as well as setting NRN to the appropriate seeds. |
| 2674 | |
| 2675 | Examples of error messages: |
| 2676 | |
| 2677 | HWWARN CALLED FROM SUBPROGRAM HWSBRN: CODE = 101 |
| 2678 | EVENT 31: SEEDS = 422399901 & 771980111 WEIGHT = 0.3893E-08 |
| 2679 | EVENT KILLED. EXECUTION CONTINUES |
| 2680 | |
| 2681 | Spacelike (initial-state) parton branching had no phase space. This |
| 2682 | can happen due to cutoffs which are slightly different in the hard |
| 2683 | subprocess and the parton shower. |
| 2684 | Action taken: program throws away this event and starts a new one. |
| 2685 | |
| 2686 | HWWARN CALLED FROM SUBPROGRAM HWCHAD: CODE = 102 |
| 2687 | EVENT 51: SEEDS = 1033784787 & 1428957533 WEIGHT = 0.3893E-08 |
| 2688 | EVENT KILLED. EXECUTION CONTINUES |
| 2689 | |
| 2690 | A cluster has been formed with too low a mass to represent any hadron |
| 2691 | of the correct flavour, and there is no colour-connected cluster from |
| 2692 | which the necessary additional mass could be transferred. |
| 2693 | Action taken: program throws away this event and starts a new one. |
| 2694 | |
| 2695 | HWWARN CALLED FROM SUBPROGRAM HWUINE: CODE= 200 |
| 2696 | EVENT SURVIVES. RUN ENDS GRACEFULLY |
| 2697 | |
| 2698 | CPU time limit liable to be reached before generating MAXEV events. |
| 2699 | Action taken: skips to terminal calculations using existing events. |
| 2700 | |
| 2701 | HWWARN CALLED FROM SUBPROGRAM HWBSUD: CODE= 500 |
| 2702 | RUN CANNOT CONTINUE |
| 2703 | |
| 2704 | The table of Sudakov form factors read on unit LRSUD does not extend |
| 2705 | to the maximum momentum scale (QLIM) specified for this run. |
| 2706 | Action taken: run aborted. The user must either reduce QLIM or set |
| 2707 | LRSUD=0 to make a bigger table (set LWSUD nonzero to write it). |
| 2708 | |
| 2709 | HWWARN CALLED FROM SUBPROGRAM HWBSUD: CODE= 515 |
| 2710 | RUN CANNOT CONTINUE |
| 2711 | |
| 2712 | The table of Sudakov form factors read on unit LRSUD is for a diff- |
| 2713 | erent value of a relevant parameter (in this case the b quark mass). |
| 2714 | Action taken: run aborted. The user must make a new table (set LWSUD |
| 2715 | nonzero to write it). |
| 2716 | ------------------------------------------------------------------------ |
| 2717 | ****** 21. SAMPLE OUTPUT ****** |
| 2718 | |
| 2719 | Below we give a complete listing of output from version 5.9 of the |
| 2720 | program, set up for t quark production in pbar-p collisions at a |
| 2721 | c.m. energy of 1.8 TeV. To shorten the event record, the underlying |
| 2722 | event has been turned off (IPROC = 11706) and production vertices are |
| 2723 | not printed (PRVTX=.FALSE.). The main features of the output are |
| 2724 | discussed in section 22. |
| 2725 | |
| 2726 | |
| 2727 | HERWIG 5.9 22nd July 1996 |
| 2728 | |
| 2729 | Please reference: G. Marchesini, B.R. Webber, |
| 2730 | G.Abbiendi, I.G.Knowles, M.H.Seymour & L.Stanco |
| 2731 | Computer Physics Communications 67 (1992) 465 |
| 2732 | |
| 2733 | INPUT CONDITIONS FOR THIS RUN |
| 2734 | |
| 2735 | BEAM 1 (PBAR ) MOM. = 900.00 |
| 2736 | BEAM 2 (P ) MOM. = 900.00 |
| 2737 | PROCESS CODE (IPROC) = 11706 |
| 2738 | NUMBER OF FLAVOURS = 6 |
| 2739 | STRUCTURE FUNCTION SET = 5 |
| 2740 | AZIM SPIN CORRELATIONS = T |
| 2741 | AZIM SOFT CORRELATIONS = T |
| 2742 | QCD LAMBDA (GEV) = 0.1800 |
| 2743 | DOWN QUARK MASS = 0.3200 |
| 2744 | UP QUARK MASS = 0.3200 |
| 2745 | STRANGE QUARK MASS = 0.5000 |
| 2746 | CHARMED QUARK MASS = 1.5500 |
| 2747 | BOTTOM QUARK MASS = 4.9500 |
| 2748 | TOP QUARK MASS = 170.0000 |
| 2749 | GLUON EFFECTIVE MASS = 0.7500 |
| 2750 | EXTRA SHOWER CUTOFF (Q)= 0.4800 |
| 2751 | EXTRA SHOWER CUTOFF (G)= 0.1000 |
| 2752 | PHOTON SHOWER CUTOFF = 0.4000 |
| 2753 | CLUSTER MASS PARAMETER = 3.3500 |
| 2754 | SPACELIKE EVOLN CUTOFF = 2.5000 |
| 2755 | INTRINSIC P-TRAN (RMS) = 0.0000 |
| 2756 | MIN P-TRAN FOR 2->2 = 10.0000 |
| 2757 | MAX P-TRAN FOR 2->2 = 900.0002 |
| 2758 | |
| 2759 | NO EVENTS WILL BE WRITTEN TO DISK |
| 2760 | |
| 2761 | B_d: Delt-M/Gam =0.7000 Delt-Gam/2*Gam =0.0000 |
| 2762 | B_s: Delt-M/Gam = 10.00 Delt-Gam/2*Gam =0.2000 |
| 2763 | |
| 2764 | PDFLIB NOT USED FOR BEAM 1 |
| 2765 | PDFLIB NOT USED FOR BEAM 2 |
| 2766 | |
| 2767 | |
| 2768 | Checking consistency of particle properties |
| 2769 | |
| 2770 | |
| 2771 | Checking consistency of decay tables |
| 2772 | |
| 2773 | Line, 565 decay: LMBDA_C+ --> XI*0 K*+ |
| 2774 | is kinematically not allowed, Min-Mout= -0.139 |
| 2775 | LMBDA_C+: BR sum = 0.97800 |
| 2776 | Rescaling to 1 |
| 2777 | |
| 2778 | Line, 990 decay: LMBDA_C- --> XI*BAR K*- |
| 2779 | is kinematically not allowed, Min-Mout= -0.139 |
| 2780 | LMBDA_C-: BR sum = 0.97800 |
| 2781 | Rescaling to 1 |
| 2782 | |
| 2783 | |
| 2784 | PARTICLE TYPE 21=PI0 SET STABLE |
| 2785 | |
| 2786 | INITIAL SEARCH FOR MAX WEIGHT |
| 2787 | |
| 2788 | PROCESS CODE IPROC = 11706 |
| 2789 | RANDOM NO. SEED 1 = 1246579 |
| 2790 | SEED 2 = 8447766 |
| 2791 | NUMBER OF SHOTS = 2000 |
| 2792 | NEW MAXIMUM WEIGHT = 1.1503371195500599E-03 |
| 2793 | NEW MAXIMUM WEIGHT = 3.2720875047931022E-03 |
| 2794 | NEW MAXIMUM WEIGHT = 3.4397725453424351E-02 |
| 2795 | NEW MAXIMUM WEIGHT = 6.0381232770162795E-02 |
| 2796 | NEW MAXIMUM WEIGHT = 6.6570674949068473E-02 |
| 2797 | |
| 2798 | INITIAL SEARCH FINISHED |
| 2799 | |
| 2800 | OUTPUT ON ELEMENTARY PROCESS |
| 2801 | |
| 2802 | NUMBER OF EVENTS = 0 |
| 2803 | NUMBER OF WEIGHTS = 2000 |
| 2804 | MEAN VALUE OF WGT = 4.5373E-03 |
| 2805 | RMS SPREAD IN WGT = 9.3312E-03 |
| 2806 | ACTUAL MAX WEIGHT = 6.0519E-02 |
| 2807 | ASSUMED MAX WEIGHT = 6.6571E-02 |
| 2808 | |
| 2809 | PROCESS CODE IPROC = 11706 |
| 2810 | CROSS SECTION (PB) = 4.537 |
| 2811 | ERROR IN C-S (PB) = 0.2087 |
| 2812 | EFFICIENCY PERCENT = 6.816 |
| 2813 | |
| 2814 | |
| 2815 | |
| 2816 | EVENT 39: 900.00 GEV/C PBAR ON 900.00 GEV/C P PROCESS: 11706 |
| 2817 | |
| 2818 | SEEDS: 875163092 & 655954870 STATUS: 100 ERROR: 0 WEIGHT: 0.4537E-02 |
| 2819 | |
| 2820 | ---INITIAL STATE--- |
| 2821 | |
| 2822 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 2823 | 1 PBAR -2212 101 0 0 0 0 0.00 0.00 900.00 900.00 0.94 |
| 2824 | 2 P 2212 102 0 0 0 0 0.00 0.00 -900.00 900.00 0.94 |
| 2825 | 3 CMF 0 103 1 2 0 0 0.00 0.00 0.00 1800.00 1800.00 |
| 2826 | |
| 2827 | ---HARD SUBPROCESS--- |
| 2828 | |
| 2829 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 2830 | 4 UBAR -2 121 6 7 9 5 0.00 0.00 312.09 312.09 0.32 |
| 2831 | 5 UQRK 2 122 6 4 17 8 0.00 0.00 -169.95 169.95 0.32 |
| 2832 | 6 HARD 0 120 4 5 7 8 -16.42 -3.93 142.14 482.34 460.61 |
| 2833 | 7 TBAR -6 123 6 8 22 4 116.29 -61.69 157.43 266.49 170.00 |
| 2834 | 8 TQRK 6 124 6 5 24 7 -116.29 61.69 -15.29 215.55 170.00 |
| 2835 | |
| 2836 | ---PARTON SHOWERS--- |
| 2837 | |
| 2838 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 2839 | 9 UBAR 94 141 4 6 11 16 -19.27 -6.00 314.16 310.83 -49.90 |
| 2840 | 10 CONE 0 100 4 7 0 0 0.88 -0.47 0.53 1.13 0.00 |
| 2841 | 11 UBARDBAR -2101 2 9 12 45 21 0.00 0.00 408.95 408.95 0.70 |
| 2842 | 12 GLUON 21 2 9 13 46 47 8.42 0.19 140.64 140.89 0.75 |
| 2843 | 13 GLUON 21 2 9 14 48 49 2.07 -1.20 14.47 14.68 0.75 |
| 2844 | 14 DBAR -1 2 9 15 50 49 3.78 3.25 8.85 10.16 0.32 |
| 2845 | 15 DQRK 1 2 9 16 51 50 3.65 2.24 9.47 10.40 0.32 |
| 2846 | 16 GLUON 21 2 9 26 52 53 1.36 1.52 3.46 4.09 0.75 |
| 2847 | 17 UQRK 94 142 5 6 19 21 2.85 2.07 -172.02 171.51 -13.73 |
| 2848 | 18 CONE 0 100 5 8 0 0 -0.88 0.47 0.07 1.00 0.00 |
| 2849 | 19 GLUON 21 2 17 20 54 55 -0.95 -0.97 -3.31 3.66 0.75 |
| 2850 | 20 GLUON 21 2 17 21 56 57 -1.90 -1.10 -16.01 16.17 0.75 |
| 2851 | 21 UD 2101 2 17 45 58 57 0.00 0.00 -708.66 708.66 1.04 |
| 2852 | 22 TBAR 94 143 7 6 23 23 107.70 -63.75 156.89 263.01 170.00 |
| 2853 | 23 TBAR -6 3 22 22 26 26 107.70 -63.75 156.89 263.01 170.00 |
| 2854 | 24 TQRK 94 144 8 6 25 25 -124.12 59.82 -14.74 219.32 170.00 |
| 2855 | 25 TQRK 6 3 24 24 37 37 -124.12 59.82 -14.74 219.32 170.00 |
| 2856 | |
| 2857 | ---HEAVY FLAVOUR DECAYS--- |
| 2858 | |
| 2859 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 2860 | 26 TBAR -6 155 22 37 27 29 107.70 -63.75 156.89 263.01 170.00 |
| 2861 | 27 MU- 13 123 26 28 30 28 18.31 32.76 65.37 75.38 0.11 |
| 2862 | 28 NU_MUBAR -14 124 26 27 31 27 80.30 -57.83 106.04 145.04 0.00 |
| 2863 | 29 BBAR -5 124 26 26 32 26 9.09 -38.68 -14.52 42.60 4.95 |
| 2864 | 30 MU- 13 1 27 26 0 0 17.82 31.88 63.62 73.36 0.11 |
| 2865 | 31 NU_MUBAR -14 1 28 26 0 0 78.14 -56.28 103.19 141.14 0.00 |
| 2866 | |
| 2867 | ---PARTON SHOWERS--- |
| 2868 | |
| 2869 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 2870 | 32 BBAR 94 144 29 26 34 36 11.74 -39.36 -9.92 48.52 23.85 |
| 2871 | 33 CONE 0 100 29 26 0 0 0.24 0.72 1.07 1.32 0.00 |
| 2872 | 34 GLUON 21 2 32 35 59 60 -2.95 -0.95 -3.35 4.62 0.75 |
| 2873 | 35 GLUON 21 2 32 36 61 62 -1.72 -1.41 -1.55 2.81 0.75 |
| 2874 | 36 BBAR -5 2 32 44 63 62 16.41 -37.00 -5.02 41.08 4.95 |
| 2875 | |
| 2876 | ---HEAVY FLAVOUR DECAYS--- |
| 2877 | |
| 2878 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 2879 | 37 TQRK 6 155 24 19 38 40 -124.12 59.82 -14.74 219.32 170.00 |
| 2880 | 38 NU_E 12 123 37 39 41 39 -96.15 66.72 23.37 119.34 0.00 |
| 2881 | 39 E+ -11 124 37 38 42 38 6.38 13.33 -54.59 56.56 0.00 |
| 2882 | 40 BQRK 5 124 37 37 43 37 -34.36 -20.23 16.48 43.43 4.95 |
| 2883 | 41 NU_E 12 1 38 37 0 0 -96.15 66.72 23.37 119.34 0.00 |
| 2884 | 42 E+ -11 1 39 37 0 0 6.38 13.33 -54.59 56.56 0.00 |
| 2885 | |
| 2886 | ---PARTON SHOWERS--- |
| 2887 | |
| 2888 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 2889 | 43 BQRK 94 144 40 37 44 44 -34.36 -20.23 16.48 43.43 4.95 |
| 2890 | 44 BQRK 5 2 43 54 64 63 -34.36 -20.23 16.48 43.43 4.95 |
| 2891 | |
| 2892 | ---GLUON SPLITTING--- |
| 2893 | |
| 2894 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 2895 | 45 UBARDBAR -2101 161 9 65 85 58 0.01 0.00 279.95 279.95 0.64 |
| 2896 | 46 UBAR -2 158 9 47 104 84 1.90 0.01 33.44 33.50 0.32 |
| 2897 | 47 UQRK 2 158 9 69 86 46 3.96 0.11 64.98 65.11 0.32 |
| 2898 | 48 DBAR -1 158 9 49 97 70 0.95 -0.68 7.08 7.18 0.32 |
| 2899 | 49 DQRK 1 158 9 71 87 48 0.40 -0.05 2.32 2.38 0.32 |
| 2900 | 50 DBAR -1 158 9 51 98 72 3.00 2.57 7.04 8.08 0.32 |
| 2901 | 51 DQRK 1 158 9 52 88 50 3.65 2.24 9.47 10.40 0.32 |
| 2902 | 52 DBAR -1 158 9 53 88 51 0.49 0.47 0.95 1.21 0.32 |
| 2903 | 53 DQRK 1 158 9 73 89 52 0.79 0.96 2.29 2.62 0.32 |
| 2904 | 54 DBAR -1 158 17 55 102 80 -0.23 -0.13 -0.54 0.68 0.32 |
| 2905 | 55 DQRK 1 158 17 56 90 54 -0.62 -0.80 -2.35 2.58 0.32 |
| 2906 | 56 DBAR -1 158 17 57 90 55 -1.18 -0.54 -8.28 8.38 0.32 |
| 2907 | 57 DQRK 1 158 17 75 91 56 -0.34 -0.26 -5.03 5.06 0.32 |
| 2908 | 58 UD 2101 162 17 45 96 68 0.00 0.00 -552.77 552.77 0.64 |
| 2909 | 59 DBAR -1 158 32 60 99 74 -0.85 -0.40 -0.95 1.37 0.32 |
| 2910 | 60 DQRK 1 158 32 61 92 59 -1.65 -0.34 -1.90 2.56 0.32 |
| 2911 | 61 DBAR -1 158 32 62 92 60 -0.66 -0.74 -0.83 1.33 0.32 |
| 2912 | 62 DQRK 1 158 32 77 93 61 -0.91 -0.59 -0.62 1.29 0.32 |
| 2913 | 63 BBAR -5 158 32 64 101 78 14.03 -31.87 -4.37 35.44 4.95 |
| 2914 | 64 BQRK 5 158 43 81 94 63 -24.17 -14.23 11.39 30.68 4.95 |
| 2915 | 65 DBAR -1 159 9 66 85 45 0.06 0.00 30.61 30.61 0.32 |
| 2916 | 66 DQRK 1 159 9 83 95 65 0.02 0.00 65.93 65.93 0.32 |
| 2917 | 67 UBAR -2 159 17 68 100 76 0.00 0.00 -108.31 108.31 0.32 |
| 2918 | 68 UQRK 2 159 17 58 96 67 -0.02 -0.02 -26.64 26.65 0.32 |
| 2919 | 69 DBAR -1 159 9 70 86 47 0.44 -0.20 4.71 4.75 0.32 |
| 2920 | 70 DQRK 1 159 9 48 97 69 2.01 0.04 32.91 32.97 0.32 |
| 2921 | 71 SBAR -3 159 9 72 87 49 0.67 0.43 2.09 2.29 0.50 |
| 2922 | 72 SQRK 3 159 9 50 98 71 0.55 0.00 2.95 3.04 0.50 |
| 2923 | 73 UBAR -2 159 32 74 89 53 -0.35 -0.15 -0.36 0.61 0.32 |
| 2924 | 74 UQRK 2 159 9 59 99 73 -0.02 0.04 0.09 0.33 0.32 |
| 2925 | 75 SBAR -3 159 17 76 91 57 -0.10 -0.08 -15.37 15.37 0.50 |
| 2926 | 76 SQRK 3 159 17 67 100 75 -0.26 -0.20 -8.28 8.30 0.50 |
| 2927 | 77 SBAR -3 159 32 78 93 62 1.73 -3.90 -0.53 4.33 0.50 |
| 2928 | 78 SQRK 3 159 32 63 101 77 0.49 -1.31 -0.22 1.50 0.50 |
| 2929 | 79 DBAR -1 159 17 80 103 82 -0.22 -0.12 -0.18 0.45 0.32 |
| 2930 | 80 DQRK 1 159 43 54 102 79 -3.20 -1.89 1.55 4.04 0.32 |
| 2931 | 81 UBAR -2 159 17 82 94 64 -1.26 -0.74 0.58 1.61 0.32 |
| 2932 | 82 UQRK 2 159 43 79 103 81 -5.60 -3.30 2.72 7.05 0.32 |
| 2933 | 83 DBAR -1 159 9 84 95 66 0.07 0.00 27.33 27.33 0.32 |
| 2934 | 84 DQRK 1 159 9 46 104 83 0.23 0.00 11.57 11.58 0.32 |
| 2935 | |
| 2936 | ---CLUSTER FORMATION--- |
| 2937 | |
| 2938 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 2939 | 85 CLUS 91 184 45 65 105 106 0.07 0.00 310.56 310.56 1.23 |
| 2940 | 86 CLUS 91 183 47 69 107 108 4.40 -0.09 69.69 69.85 1.59 |
| 2941 | 87 CLUS 91 183 49 71 109 110 1.07 0.38 4.41 4.67 1.03 |
| 2942 | 88 CLUS 91 183 51 52 111 112 4.14 2.70 10.42 11.61 1.31 |
| 2943 | 89 CLUS 91 183 53 73 113 114 0.44 0.80 1.92 3.24 2.44 |
| 2944 | 90 CLUS 91 183 55 56 115 116 -1.80 -1.34 -10.63 10.96 1.48 |
| 2945 | 91 CLUS 91 183 57 75 117 118 -0.44 -0.34 -20.39 20.43 1.09 |
| 2946 | 92 CLUS 91 183 60 61 119 120 -2.31 -1.08 -2.73 3.89 1.09 |
| 2947 | 93 CLUS 91 183 62 77 121 122 0.82 -4.49 -1.15 5.62 3.07 |
| 2948 | 94 CLUS 91 183 64 81 123 123 -25.44 -14.98 11.97 32.29 5.28 |
| 2949 | 95 CLUS 91 183 66 83 124 125 0.09 0.00 93.26 93.26 0.71 |
| 2950 | 96 CLUS 91 185 68 58 126 127 -0.02 -0.02 -579.41 579.41 1.64 |
| 2951 | 97 CLUS 91 183 70 48 128 129 2.97 -0.64 39.98 40.15 2.04 |
| 2952 | 98 CLUS 91 183 72 50 130 131 3.54 2.57 9.99 11.12 2.17 |
| 2953 | 99 CLUS 91 183 74 59 132 133 -0.87 -0.36 -0.86 1.71 1.13 |
| 2954 | 100 CLUS 91 183 76 67 134 135 -0.26 -0.20 -116.59 116.61 2.24 |
| 2955 | 101 CLUS 91 183 78 63 136 136 14.56 -33.17 -4.60 36.91 5.38 |
| 2956 | 102 CLUS 91 183 80 54 137 138 -3.47 -2.02 1.02 4.76 2.34 |
| 2957 | 103 CLUS 91 183 82 79 139 140 -5.81 -3.42 2.54 7.49 2.06 |
| 2958 | 104 CLUS 91 183 84 46 141 142 2.13 0.01 45.01 45.08 1.04 |
| 2959 | |
| 2960 | ---CLUSTER DECAYS--- |
| 2961 | |
| 2962 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 2963 | 105 PBAR -2212 1 85 9 0 0 -0.13 0.09 215.09 215.09 0.94 |
| 2964 | 106 PI+ 211 1 85 9 0 0 0.20 -0.09 95.47 95.47 0.14 |
| 2965 | 107 OMEGA 223 197 86 9 143 145 2.33 -0.03 34.12 34.20 0.78 |
| 2966 | 108 RHO+ 213 197 86 9 146 147 2.07 -0.06 35.58 35.65 0.77 |
| 2967 | 109 PI0 111 1 87 9 0 0 0.14 0.05 0.57 0.60 0.14 |
| 2968 | 110 K*0 313 197 87 9 148 149 0.93 0.34 3.84 4.07 0.90 |
| 2969 | 111 PI0 111 1 88 9 0 0 2.48 1.51 6.44 7.07 0.14 |
| 2970 | 112 OMEGA 223 197 88 9 150 151 1.66 1.19 3.98 4.54 0.78 |
| 2971 | 113 P 2212 1 89 9 0 0 -0.35 0.36 0.89 1.39 0.94 |
| 2972 | 114 DLTABR-- -2224 197 89 9 152 153 0.80 0.45 1.03 1.85 1.23 |
| 2973 | 115 A_10 20113 197 90 17 154 155 -1.73 -1.30 -10.33 10.63 1.23 |
| 2974 | 116 PI0 111 1 90 17 0 0 -0.06 -0.04 -0.30 0.33 0.14 |
| 2975 | 117 PI- -211 1 91 17 0 0 -0.08 0.11 -12.23 12.23 0.14 |
| 2976 | 118 K+ 321 1 91 17 0 0 -0.36 -0.44 -8.16 8.20 0.49 |
| 2977 | 119 RHO- -213 197 92 32 156 157 -1.94 -1.07 -2.51 3.44 0.77 |
| 2978 | 120 PI+ 211 1 92 32 0 0 -0.37 0.00 -0.22 0.45 0.14 |
| 2979 | 121 KL_10 10313 197 93 32 158 159 1.17 -2.31 -1.07 3.22 1.57 |
| 2980 | 122 ETAP 331 197 93 32 160 162 -0.35 -2.18 -0.08 2.41 0.96 |
| 2981 | 123 B- -521 196 94 43 163 165 -25.44 -14.98 11.97 32.29 5.28 |
| 2982 | 124 PI0 111 1 95 9 0 0 0.30 -0.06 25.24 25.24 0.14 |
| 2983 | 125 PI0 111 1 95 9 0 0 -0.21 0.06 68.02 68.02 0.14 |
| 2984 | 126 PI+ 211 1 96 17 0 0 0.04 0.14 -231.52 231.52 0.14 |
| 2985 | 127 DELTA0 2114 197 96 17 166 167 -0.06 -0.15 -347.89 347.89 1.23 |
| 2986 | 128 P 2212 1 97 9 0 0 0.84 -0.11 14.92 14.97 0.94 |
| 2987 | 129 PBAR -2212 1 97 9 0 0 2.13 -0.53 25.06 25.17 0.94 |
| 2988 | 130 ETA 221 197 98 9 168 170 0.59 0.27 2.25 2.40 0.55 |
| 2989 | 131 K*_2BAR0 -315 197 98 9 171 172 2.95 2.30 7.74 8.72 1.43 |
| 2990 | 132 PI0 111 1 99 9 0 0 -0.35 0.05 -0.95 1.02 0.14 |
| 2991 | 133 PI+ 211 1 99 9 0 0 -0.52 -0.41 0.09 0.68 0.14 |
| 2992 | 134 KBAR0 -311 197 100 17 173 173 0.04 -0.01 -17.14 17.15 0.50 |
| 2993 | 135 PI_2- -10215 197 100 17 174 175 -0.30 -0.19 -99.44 99.46 1.67 |
| 2994 | 136 B_S0 531 200 101 32 176 176 14.56 -33.17 -4.60 36.91 5.38 |
| 2995 | 137 HL_10 10223 197 102 43 177 178 -3.20 -1.92 1.24 4.10 1.17 |
| 2996 | 138 ETA 221 197 102 43 179 181 -0.28 -0.10 -0.22 0.66 0.55 |
| 2997 | 139 A_20 115 197 103 43 182 184 -2.96 -1.35 1.04 3.66 1.32 |
| 2998 | 140 PI+ 211 1 103 43 0 0 -2.85 -2.07 1.50 3.84 0.14 |
| 2999 | 141 PI0 111 1 104 9 0 0 0.66 0.06 16.64 16.65 0.14 |
| 3000 | 142 RHO- -213 197 104 9 185 186 1.47 -0.05 28.37 28.42 0.77 |
| 3001 | |
| 3002 | ---STRONG HADRON DECAYS--- |
| 3003 | |
| 3004 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3005 | 143 PI+ 211 1 107 9 0 0 1.90 -0.02 24.27 24.35 0.14 |
| 3006 | 144 PI- -211 1 107 9 0 0 0.32 0.00 6.77 6.78 0.14 |
| 3007 | 145 PI0 111 1 107 9 0 0 0.11 -0.02 3.07 3.08 0.14 |
| 3008 | 146 PI+ 211 1 108 9 0 0 1.80 0.19 29.01 29.07 0.14 |
| 3009 | 147 PI0 111 1 108 9 0 0 0.27 -0.25 6.57 6.58 0.14 |
| 3010 | 148 K0 311 198 110 9 187 187 0.65 0.06 3.19 3.29 0.50 |
| 3011 | 149 PI0 111 1 110 9 0 0 0.28 0.27 0.65 0.77 0.14 |
| 3012 | 150 PI0 111 1 112 9 0 0 1.33 1.12 3.73 4.12 0.14 |
| 3013 | 151 GAMMA 22 1 112 9 0 0 0.34 0.07 0.25 0.42 0.00 |
| 3014 | 152 PBAR -2212 1 114 9 0 0 0.75 0.24 1.02 1.59 0.94 |
| 3015 | 153 PI- -211 1 114 9 0 0 0.05 0.21 0.01 0.25 0.14 |
| 3016 | 154 RHO+ 213 198 115 17 188 189 -1.57 -0.83 -8.84 9.05 0.77 |
| 3017 | 155 PI- -211 1 115 17 0 0 -0.16 -0.47 -1.49 1.58 0.14 |
| 3018 | 156 PI- -211 1 119 32 0 0 -0.65 -0.64 -1.38 1.66 0.14 |
| 3019 | 157 PI0 111 1 119 32 0 0 -1.29 -0.43 -1.12 1.77 0.14 |
| 3020 | 158 K+ 321 1 121 32 0 0 0.56 -0.88 0.04 1.15 0.49 |
| 3021 | 159 RHO- -213 198 121 32 190 191 0.61 -1.43 -1.11 2.06 0.77 |
| 3022 | 160 PI+ 211 1 122 32 0 0 -0.15 -0.86 0.05 0.89 0.14 |
| 3023 | 161 PI- -211 1 122 32 0 0 -0.07 -0.48 -0.08 0.51 0.14 |
| 3024 | 162 ETA 221 198 122 32 192 193 -0.13 -0.84 -0.05 1.01 0.55 |
| 3025 | 163 RHO0 113 198 123 43 194 195 -18.44 -9.34 6.79 21.77 0.77 |
| 3026 | 164 E- 11 1 123 43 0 0 -6.49 -5.26 5.27 9.88 0.00 |
| 3027 | 165 NU_EBAR -12 1 123 43 0 0 -0.50 -0.38 -0.09 0.63 0.00 |
| 3028 | 166 P 2212 1 127 17 0 0 0.09 -0.11 -219.33 219.33 0.94 |
| 3029 | 167 PI- -211 1 127 17 0 0 -0.15 -0.05 -128.56 128.56 0.14 |
| 3030 | 168 PI0 111 1 130 9 0 0 0.07 0.07 0.80 0.82 0.14 |
| 3031 | 169 PI0 111 1 130 9 0 0 0.21 0.13 0.47 0.55 0.14 |
| 3032 | 170 PI0 111 1 130 9 0 0 0.31 0.07 0.98 1.04 0.14 |
| 3033 | 171 K- -321 1 131 9 0 0 2.36 1.08 5.22 5.85 0.49 |
| 3034 | 172 PI+ 211 1 131 9 0 0 0.59 1.22 2.53 2.87 0.14 |
| 3035 | 173 K_S0 310 198 134 17 196 197 0.04 -0.01 -17.14 17.15 0.50 |
| 3036 | 174 F_2 225 198 135 17 198 199 -0.33 -0.32 -95.89 95.90 1.27 |
| 3037 | 175 PI- -211 1 135 17 0 0 0.03 0.12 -3.56 3.56 0.14 |
| 3038 | 176 B_SBAR0 -531 199 136 32 207 208 14.56 -33.17 -4.60 36.91 5.38 |
| 3039 | 177 RHO+ 213 198 137 43 200 201 -2.29 -1.73 0.99 3.13 0.77 |
| 3040 | 178 PI- -211 1 137 43 0 0 -0.90 -0.19 0.24 0.96 0.14 |
| 3041 | 179 PI0 111 1 138 43 0 0 0.01 0.05 0.02 0.15 0.14 |
| 3042 | 180 PI0 111 1 138 43 0 0 -0.07 -0.10 -0.06 0.19 0.14 |
| 3043 | 181 PI0 111 1 138 43 0 0 -0.22 -0.05 -0.18 0.32 0.14 |
| 3044 | 182 OMEGA 223 198 139 43 202 204 -1.92 -0.63 0.73 2.28 0.78 |
| 3045 | 183 PI+ 211 1 139 43 0 0 -0.66 -0.32 0.05 0.75 0.14 |
| 3046 | 184 PI- -211 1 139 43 0 0 -0.38 -0.40 0.26 0.63 0.14 |
| 3047 | 185 PI- -211 1 142 9 0 0 0.68 -0.38 13.27 13.29 0.14 |
| 3048 | 186 PI0 111 1 142 9 0 0 0.79 0.33 15.11 15.13 0.14 |
| 3049 | 187 K_S0 310 198 148 9 205 206 0.65 0.06 3.19 3.29 0.50 |
| 3050 | 188 PI+ 211 1 154 17 0 0 -1.45 -0.73 -8.47 8.62 0.14 |
| 3051 | 189 PI0 111 1 154 17 0 0 -0.13 -0.10 -0.37 0.43 0.14 |
| 3052 | 190 PI- -211 1 159 32 0 0 0.68 -1.24 -1.13 1.82 0.14 |
| 3053 | 191 PI0 111 1 159 32 0 0 -0.06 -0.19 0.02 0.24 0.14 |
| 3054 | 192 GAMMA 22 1 162 32 0 0 -0.31 -0.62 -0.15 0.71 0.00 |
| 3055 | 193 GAMMA 22 1 162 32 0 0 0.18 -0.22 0.10 0.30 0.00 |
| 3056 | 194 PI+ 211 1 163 43 0 0 -16.47 -8.12 6.03 19.32 0.14 |
| 3057 | 195 PI- -211 1 163 43 0 0 -1.98 -1.22 0.76 2.45 0.14 |
| 3058 | 196 PI0 111 1 173 17 0 0 0.14 0.16 -6.36 6.37 0.14 |
| 3059 | 197 PI0 111 1 173 17 0 0 -0.10 -0.16 -10.78 10.78 0.14 |
| 3060 | 198 PI0 111 1 174 17 0 0 -0.61 -0.52 -38.85 38.86 0.14 |
| 3061 | 199 PI0 111 1 174 17 0 0 0.27 0.20 -57.03 57.04 0.14 |
| 3062 | 200 PI+ 211 1 177 43 0 0 -1.01 -0.34 0.30 1.11 0.14 |
| 3063 | 201 PI0 111 1 177 43 0 0 -1.29 -1.39 0.70 2.02 0.14 |
| 3064 | 202 PI+ 211 1 182 43 0 0 -0.30 -0.02 0.08 0.34 0.14 |
| 3065 | 203 PI- -211 1 182 43 0 0 -0.30 -0.13 0.36 0.50 0.14 |
| 3066 | 204 PI0 111 1 182 43 0 0 -1.32 -0.48 0.29 1.44 0.14 |
| 3067 | 205 PI0 111 1 187 9 0 0 0.51 -0.06 1.56 1.65 0.14 |
| 3068 | 206 PI0 111 1 187 9 0 0 0.14 0.12 1.63 1.64 0.14 |
| 3069 | |
| 3070 | ---HEAVY FLAVOUR DECAYS--- |
| 3071 | |
| 3072 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3073 | 207 BQRK 5 155 176 208 209 211 13.20 -30.08 -4.17 33.47 4.88 |
| 3074 | 208 SBAR -3 125 176 211 212 211 1.35 -3.09 -0.43 3.43 0.50 |
| 3075 | 209 CQRK 4 123 207 210 213 210 2.30 -5.94 -0.61 6.59 1.55 |
| 3076 | 210 CBAR -4 124 207 209 215 209 3.58 -8.37 -1.74 9.40 1.55 |
| 3077 | 211 SQRK 3 124 207 207 217 207 7.33 -15.77 -1.82 17.49 0.50 |
| 3078 | 212 SBAR -3 160 208 221 223 221 1.35 -3.09 -0.43 3.43 0.50 |
| 3079 | |
| 3080 | ---PARTON SHOWERS--- |
| 3081 | |
| 3082 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3083 | 213 CQRK 94 143 209 207 214 214 2.30 -5.94 -0.61 6.59 1.55 |
| 3084 | 214 CQRK 4 2 213 216 219 216 2.30 -5.94 -0.61 6.59 1.55 |
| 3085 | 215 CBAR 94 144 210 207 216 216 3.58 -8.37 -1.74 9.40 1.55 |
| 3086 | 216 CBAR -4 2 215 219 220 219 3.58 -8.37 -1.74 9.40 1.55 |
| 3087 | 217 SQRK 94 144 211 207 218 218 7.33 -15.77 -1.82 17.49 0.50 |
| 3088 | 218 SQRK 3 2 217 212 221 212 7.33 -15.77 -1.82 17.49 0.50 |
| 3089 | |
| 3090 | ---GLUON SPLITTING--- |
| 3091 | |
| 3092 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3093 | 219 CQRK 4 158 213 220 222 220 2.30 -5.94 -0.61 6.59 1.55 |
| 3094 | 220 CBAR -4 158 215 219 222 219 3.58 -8.37 -1.74 9.40 1.55 |
| 3095 | 221 SQRK 3 158 217 212 223 212 7.33 -15.77 -1.82 17.49 0.50 |
| 3096 | |
| 3097 | ---CLUSTER FORMATION--- |
| 3098 | |
| 3099 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3100 | 222 CLUS 91 183 219 220 224 224 4.87 -12.18 -2.12 13.62 2.98 |
| 3101 | 223 CLUS 91 183 221 212 225 226 9.69 -20.99 -2.48 23.29 1.37 |
| 3102 | |
| 3103 | ---CLUSTER DECAYS--- |
| 3104 | |
| 3105 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3106 | 224 ETA_C 441 199 222 213 227 229 4.87 -12.18 -2.12 13.62 2.98 |
| 3107 | 225 K- -321 1 223 217 0 0 8.22 -17.67 -2.03 19.60 0.49 |
| 3108 | 226 K+ 321 1 223 217 0 0 1.47 -3.31 -0.45 3.69 0.49 |
| 3109 | |
| 3110 | ---HEAVY FLAVOUR DECAYS--- |
| 3111 | |
| 3112 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3113 | 227 GLUON 21 123 224 229 230 228 2.59 -4.45 -1.11 5.32 0.75 |
| 3114 | 228 GLUON 21 124 224 227 232 229 0.84 -4.20 -0.51 4.38 0.75 |
| 3115 | 229 GLUON 21 124 224 228 234 227 1.44 -3.53 -0.50 3.92 0.75 |
| 3116 | |
| 3117 | ---PARTON SHOWERS--- |
| 3118 | |
| 3119 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3120 | 230 GLUON 94 143 227 224 231 231 2.59 -4.45 -1.11 5.32 0.75 |
| 3121 | 231 GLUON 21 2 230 235 236 237 2.59 -4.45 -1.11 5.32 0.75 |
| 3122 | 232 GLUON 94 144 228 224 233 233 0.84 -4.20 -0.51 4.38 0.75 |
| 3123 | 233 GLUON 21 2 232 236 238 239 0.84 -4.20 -0.51 4.38 0.75 |
| 3124 | 234 GLUON 94 144 229 224 235 235 1.44 -3.53 -0.50 3.92 0.75 |
| 3125 | 235 GLUON 21 2 234 238 240 241 1.44 -3.53 -0.50 3.92 0.75 |
| 3126 | |
| 3127 | ---GLUON SPLITTING--- |
| 3128 | |
| 3129 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3130 | 236 DBAR -1 158 230 237 243 239 1.65 -2.62 -0.82 3.22 0.32 |
| 3131 | 237 DQRK 1 158 230 240 242 236 0.95 -1.83 -0.29 2.10 0.32 |
| 3132 | 238 DBAR -1 158 232 239 244 241 0.66 -3.17 -0.34 3.27 0.32 |
| 3133 | 239 DQRK 1 158 232 236 243 238 0.18 -1.03 -0.17 1.11 0.32 |
| 3134 | 240 UBAR -2 158 234 241 242 237 0.65 -2.08 -0.24 2.22 0.32 |
| 3135 | 241 UQRK 2 158 234 238 244 240 0.79 -1.45 -0.26 1.70 0.32 |
| 3136 | |
| 3137 | ---CLUSTER FORMATION--- |
| 3138 | |
| 3139 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3140 | 242 CLUS 91 183 237 240 245 246 1.60 -3.90 -0.53 4.32 0.74 |
| 3141 | 243 CLUS 91 183 239 236 247 248 1.82 -3.65 -0.98 4.33 1.03 |
| 3142 | 244 CLUS 91 183 241 238 249 250 1.45 -4.62 -0.60 4.98 0.96 |
| 3143 | |
| 3144 | ---CLUSTER DECAYS--- |
| 3145 | |
| 3146 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3147 | 245 PI- -211 1 242 230 0 0 1.53 -3.79 -0.46 4.11 0.14 |
| 3148 | 246 PI0 111 1 242 230 0 0 0.06 -0.12 -0.07 0.20 0.14 |
| 3149 | 247 PI0 111 1 243 232 0 0 0.52 -0.39 0.03 0.66 0.14 |
| 3150 | 248 PI0 111 1 243 232 0 0 1.30 -3.27 -1.01 3.66 0.14 |
| 3151 | 249 PI0 111 1 244 234 0 0 1.02 -3.98 -0.74 4.18 0.14 |
| 3152 | 250 PI+ 211 1 244 234 0 0 0.43 -0.64 0.14 0.80 0.14 |
| 3153 | |
| 3154 | OUTPUT ON ELEMENTARY PROCESS |
| 3155 | |
| 3156 | NUMBER OF EVENTS = 1000 |
| 3157 | NUMBER OF WEIGHTS = 14518 |
| 3158 | MEAN VALUE OF WGT = 4.4894E-03 |
| 3159 | RMS SPREAD IN WGT = 9.2221E-03 |
| 3160 | ACTUAL MAX WEIGHT = 6.1048E-02 |
| 3161 | ASSUMED MAX WEIGHT = 6.6571E-02 |
| 3162 | |
| 3163 | PROCESS CODE IPROC = 11706 |
| 3164 | CROSS SECTION (PB) = 4.489 |
| 3165 | ERROR IN C-S (PB) = 7.6538E-02 |
| 3166 | EFFICIENCY PERCENT = 6.744 |
| 3167 | |
| 3168 | ----------------------------------------------------------------------- |
| 3169 | |
| 3170 | ****** 22. GUIDE TO SAMPLE OUTPUT ****** |
| 3171 | |
| 3172 | |
| 3173 | After listing the more important input parameter values, the program |
| 3174 | prints the message |
| 3175 | |
| 3176 | NO EVENTS WILL BE WRITTEN TO DISK |
| 3177 | |
| 3178 | to remind the user that LWEVT=0 for this run. Since BBbar oscillation |
| 3179 | is enabled (MIXING=.TRUE.), the relevant parameters are printed: |
| 3180 | |
| 3181 | B_d: Delt-M/Gam =0.7000 Delt-Gam/2*Gam =0.0000 |
| 3182 | B_s: Delt-M/Gam = 10.00 Delt-Gam/2*Gam =0.2000 |
| 3183 | |
| 3184 | The messages |
| 3185 | |
| 3186 | PDFLIB NOT USED FOR BEAM 1 |
| 3187 | PDFLIB NOT USED FOR BEAM 2 |
| 3188 | |
| 3189 | indicating that the CERN PDFLIB structure function library will not |
| 3190 | be used (MODPDF<0). Next the particle property and decay tables are |
| 3191 | checked for consistency. The messages |
| 3192 | |
| 3193 | Line, 565 decay: LMBDA_C+ --> XI*0 K*+ |
| 3194 | is kinematically not allowed, Min-Mout= -0.139 |
| 3195 | LMBDA_C+: BR sum = 0.97800 |
| 3196 | Rescaling to 1 |
| 3197 | |
| 3198 | Line, 990 decay: LMBDA_C- --> XI*BAR K*- |
| 3199 | is kinematically not allowed, Min-Mout= -0.139 |
| 3200 | LMBDA_C-: BR sum = 0.97800 |
| 3201 | Rescaling to 1 |
| 3202 | |
| 3203 | indicate that some user-modified decay modes are impossible and will |
| 3204 | be ignored. The default particle data table was modified by calling |
| 3205 | HWUSTA('PI0 ') to suppress pi0 decays, so we get the message |
| 3206 | |
| 3207 | PARTICLE TYPE 21=PI0 SET STABLE |
| 3208 | |
| 3209 | Next the program searches for the maximum weight, i.e. the maximum |
| 3210 | cross section in the available phase space, as implied by the default |
| 3211 | value WGTMAX=0. The parameters |
| 3212 | |
| 3213 | MIN P-TRAN FOR 2->2 = 10.0000 |
| 3214 | MAX P-TRAN FOR 2->2 = 900.0002 |
| 3215 | with |
| 3216 | PROCESS CODE = 11706 |
| 3217 | |
| 3218 | mean that the transverse momentum of the t quark in the QCD 2->2 hard |
| 3219 | subprocesses is required to be greater than 10 GeV/c. After this |
| 3220 | search, the estimated total cross section of relevant subprocesses in |
| 3221 | this region of phase space is printed, together with the anticipated |
| 3222 | efficiency of subprocess generation (i.e. average/maximum weight): |
| 3223 | |
| 3224 | CROSS SECTION (PB) = 4.537 |
| 3225 | ERROR IN C-S (PB) = 0.2087 |
| 3226 | EFFICIENCY PERCENT = 6.816 |
| 3227 | |
| 3228 | Since the print parameter was MAXPR=0, no events were printed by |
| 3229 | default, but the user analysis routine HWANAL called HWUEPR to print |
| 3230 | the first "interesting" event. The event heading |
| 3231 | |
| 3232 | EVENT 39: 900.00 GEV/C PBAR ON 900.00 GEV/C P PROCESS: 11706 |
| 3233 | |
| 3234 | SEEDS: 875163092 & 655954870 STATUS: 100 ERROR: 0 WEIGHT: 0.4537E-02 |
| 3235 | |
| 3236 | |
| 3237 | tells us the beam and target, the random number seeds at the start of |
| 3238 | the event and the process code IPROC. The status 100 means a complete |
| 3239 | event was generated and the zero error code means no problems were |
| 3240 | encountered. Since NOWGT=.TRUE. (unweighted event generation), each |
| 3241 | event has the mean weight computed earlier. |
| 3242 | |
| 3243 | Next come the contents of COMMON/HEPEVT/ and related quantities. The |
| 3244 | print parameter for vertex information has been set PRVTX=.FALSE. and |
| 3245 | so no space-time information is printed. The various parts of this |
| 3246 | particular event are located as follows: |
| 3247 | |
| 3248 | +---------+--------------------------------------+ |
| 3249 | | Entry | Description | |
| 3250 | +---------+--------------------------------------+ |
| 3251 | | 1- 3 | Initial state | |
| 3252 | | 4- 8 | Hard subprocess: u+ubar -> t+tbar | |
| 3253 | | 9- 25 | Parton showers | |
| 3254 | | 26- 44 | Top decays and subsequent showers | |
| 3255 | | 45- 84 | Gluon splitting | |
| 3256 | | 85-104 | Cluster formation | |
| 3257 | | 105-206 | Cluster and hadron decays | |
| 3258 | | 207-218 | Weak decay of B_sbar and showers | |
| 3259 | | 219-226 | Hadronization of B_sbar products | |
| 3260 | | 227-235 | 3-gluon decay of eta_c | |
| 3261 | | 236-250 | Hadronization of eta_c products | |
| 3262 | +---------+--------------------------------------+ |
| 3263 | |
| 3264 | We discuss each part in turn. |
| 3265 | |
| 3266 | ---INITIAL STATE--- |
| 3267 | |
| 3268 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3269 | 1 PBAR -2212 101 0 0 0 0 0.00 0.00 900.00 900.00 0.94 |
| 3270 | 2 P 2212 102 0 0 0 0 0.00 0.00 -900.00 900.00 0.94 |
| 3271 | 3 CMF 0 103 1 2 0 0 0.00 0.00 0.00 1800.00 1800.00 |
| 3272 | |
| 3273 | CMF represents the overall centre of mass of the initial state. The |
| 3274 | 'mother' MOi=JMOHEP(i,IHEP) & 'daughter' DAi=JDAHEP(i,IHEP) pointers |
| 3275 | are set to zero for these entries. |
| 3276 | |
| 3277 | ---HARD SUBPROCESS--- |
| 3278 | |
| 3279 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3280 | 4 UBAR -2 121 6 7 9 5 0.00 0.00 312.09 312.09 0.32 |
| 3281 | 5 UQRK 2 122 6 4 17 8 0.00 0.00 -169.95 169.95 0.32 |
| 3282 | 6 HARD 0 120 4 5 7 8 -16.42 -3.93 142.14 482.34 460.61 |
| 3283 | 7 TBAR -6 123 6 8 22 4 116.29 -61.69 157.43 266.49 170.00 |
| 3284 | 8 TQRK 6 124 6 5 24 7 -116.29 61.69 -15.29 215.55 170.00 |
| 3285 | |
| 3286 | HARD is the hard subprocess centre of mass. Its mother and daughter |
| 3287 | pointers give the locations of the incoming and outgoing partons. The |
| 3288 | status codes 121-124 correspond to the hard subprocess partons 1-4. |
| 3289 | The first mother pointers show the location of the hard c.m., and the |
| 3290 | second mother of each parton is the 'colour mother', as explained |
| 3291 | above. Thus the colours of partons 1234 are connected to 3142 respt., |
| 3292 | corresponding to process IHPRO=12. Likewise,the first daughter points |
| 3293 | to the associated jet but the second daughter is the colour daughter, |
| 3294 | i.e. the parton to which this one's anticolour is connected. Thus the |
| 3295 | anticolour connections of 1234 in this case are to 2413. The colour |
| 3296 | diagram is |
| 3297 | |
| 3298 | (ubar)1 --<--+ +--<-- 3(tbar) |
| 3299 | \___/ |
| 3300 | ___ |
| 3301 | / \ |
| 3302 | (u)2 -->--+ +-->-- 4(t) |
| 3303 | |
| 3304 | Note that in specifying the colour connections all lines are regarded |
| 3305 | as outgoing, and that since antiquarks carry no colour MO2 is in that |
| 3306 | case used for the flavour connection (similarly with DA2 for quarks). |
| 3307 | Gluon radiation from the initial ubar will be limited by interference |
| 3308 | with the tbar and vice-versa, that from the incoming u by the t and |
| 3309 | vice-versa. At this stage, the momenta and masses of the partons are |
| 3310 | the raw on-shell values generated before QCD radiative corrections, |
| 3311 | but HARD has been updated to give the true hard subprocess momentum |
| 3312 | after initial- and final-state parton branching. |
| 3313 | |
| 3314 | ---PARTON SHOWERS--- |
| 3315 | |
| 3316 | The QCD cascade from each hard parton is generated in sequence. First |
| 3317 | there is a jet entry (IDHEP=94) giving the total jet momentum, mass |
| 3318 | and flavour. For initial-state jets the mass represents -|q**2|**1/2 |
| 3319 | for the virtual parton entering the hard subprocess. MO1 gives the |
| 3320 | parent hard parton and MO2 the hard centre-of-mass. DO1 and DO2 point |
| 3321 | to the first and last parton in the jet after perturbative branching. |
| 3322 | If branching occurs, the next entry (CONE) is a lightlike 4-vector |
| 3323 | defining the radiation cone and the orientation of the radiation |
| 3324 | pattern. |
| 3325 | |
| 3326 | The partons in the jet (with ISTHEP set to 2 by gluon splitting sub- |
| 3327 | routine HWCGSP) have their colour and anticolour connections given |
| 3328 | by MO2 and DA2 respectively, as described for the hard subprocess. |
| 3329 | For an incoming jet, the remnants of the incoming hadrons (IHEP=11,21 |
| 3330 | here) also have ISTHEP=2. The ubar jet is: |
| 3331 | |
| 3332 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3333 | 9 UBAR 94 141 4 6 11 16 -19.27 -6.00 314.16 310.83 -49.90 |
| 3334 | 10 CONE 0 100 4 7 0 0 0.88 -0.47 0.53 1.13 0.00 |
| 3335 | 11 UBARDBAR -2101 2 9 12 45 21 0.00 0.00 408.95 408.95 0.70 |
| 3336 | 12 GLUON 21 2 9 13 46 47 8.42 0.19 140.64 140.89 0.75 |
| 3337 | 13 GLUON 21 2 9 14 48 49 2.07 -1.20 14.47 14.68 0.75 |
| 3338 | 14 DBAR -1 2 9 15 50 49 3.78 3.25 8.85 10.16 0.32 |
| 3339 | 15 DQRK 1 2 9 16 51 50 3.65 2.24 9.47 10.40 0.32 |
| 3340 | 16 GLUON 21 2 9 26 52 53 1.36 1.52 3.46 4.09 0.75 |
| 3341 | |
| 3342 | and similarly for the u jet (IHEP=17-21). The produced t and tbar are |
| 3343 | so slow in the subprocess c.o.m. frame that they do not radiate any |
| 3344 | resolvable gluons. After any showering, they're given status ISTHEP=3 |
| 3345 | and copied with ISTHEP=155 retaining the colour connection labels for |
| 3346 | the decay processes. In this event both top decays are leptonic: |
| 3347 | |
| 3348 | ---HEAVY FLAVOUR DECAYS--- |
| 3349 | |
| 3350 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3351 | 26 TBAR -6 155 22 37 27 29 107.70 -63.75 156.89 263.01 170.00 |
| 3352 | 27 MU- 13 123 26 28 30 28 18.31 32.76 65.37 75.38 0.11 |
| 3353 | 28 NU_MUBAR -14 124 26 27 31 27 80.30 -57.83 106.04 145.04 0.00 |
| 3354 | 29 BBAR -5 124 26 26 32 26 9.09 -38.68 -14.52 42.60 4.95 |
| 3355 | 30 MU- 13 1 27 26 0 0 17.82 31.88 63.62 73.36 0.11 |
| 3356 | 31 NU_MUBAR -14 1 28 26 0 0 78.14 -56.28 103.19 141.14 0.00 |
| 3357 | |
| 3358 | 37 TQRK 6 155 24 19 38 40 -124.12 59.82 -14.74 219.32 170.00 |
| 3359 | 38 NU_E 12 123 37 39 41 39 -96.15 66.72 23.37 119.34 0.00 |
| 3360 | 39 E+ -11 124 37 38 42 38 6.38 13.33 -54.59 56.56 0.00 |
| 3361 | 40 BQRK 5 124 37 37 43 37 -34.36 -20.23 16.48 43.43 4.95 |
| 3362 | 41 NU_E 12 1 38 37 0 0 -96.15 66.72 23.37 119.34 0.00 |
| 3363 | 42 E+ -11 1 39 37 0 0 6.38 13.33 -54.59 56.56 0.00 |
| 3364 | |
| 3365 | ---PARTON SHOWERS--- |
| 3366 | |
| 3367 | After the tbar decay, the resulting bbar radiates 2 gluons: |
| 3368 | |
| 3369 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3370 | 32 BBAR 94 144 29 26 34 36 11.74 -39.36 -9.92 48.52 23.85 |
| 3371 | 33 CONE 0 100 29 26 0 0 0.24 0.72 1.07 1.32 0.00 |
| 3372 | 34 GLUON 21 2 32 35 59 60 -2.95 -0.95 -3.35 4.62 0.75 |
| 3373 | 35 GLUON 21 2 32 36 61 62 -1.72 -1.41 -1.55 2.81 0.75 |
| 3374 | 36 BBAR -5 2 32 44 63 62 16.41 -37.00 -5.02 41.08 4.95 |
| 3375 | |
| 3376 | but the b quark from the t decay does not radiate. If the decays had |
| 3377 | been hadronic, the quarks from the virtual W decay would also radiate |
| 3378 | in general. |
| 3379 | |
| 3380 | ---GLUON SPLITTING--- |
| 3381 | |
| 3382 | As the first step in the cluster hadronization model, any gluons in |
| 3383 | the jets are split into light quark-antiquark pairs. The flavours of |
| 3384 | the pairs are chosen at random amongst those allowed by kinematics. |
| 3385 | The colour connections are remade accordingly. |
| 3386 | |
| 3387 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3388 | 45 UBARDBAR -2101 161 9 65 85 58 0.01 0.00 279.95 279.95 0.64 |
| 3389 | 46 UBAR -2 158 9 47 104 84 1.90 0.01 33.44 33.50 0.32 |
| 3390 | 47 UQRK 2 158 9 69 86 46 3.96 0.11 64.98 65.11 0.32 |
| 3391 | 48 DBAR -1 158 9 49 97 70 0.95 -0.68 7.08 7.18 0.32 |
| 3392 | 49 DQRK 1 158 9 71 87 48 0.40 -0.05 2.32 2.38 0.32 |
| 3393 | ....... |
| 3394 | 63 BBAR -5 158 32 64 101 78 14.03 -31.87 -4.37 35.44 4.95 |
| 3395 | 64 BQRK 5 158 43 81 94 63 -24.17 -14.23 11.39 30.68 4.95 |
| 3396 | |
| 3397 | Each quark (or antidiquark) is combined with its colour mother anti- |
| 3398 | quark (or diquark) to make a cluster with the sum of their 4-momenta. |
| 3399 | All non-beam clusters with masses above the maximum are split by |
| 3400 | creating new quark-antiquark pairs with ISTHEP=159 (10 such pairs in |
| 3401 | this event). |
| 3402 | |
| 3403 | 65 DBAR -1 159 9 66 85 45 0.06 0.00 30.61 30.61 0.32 |
| 3404 | 66 DQRK 1 159 9 83 95 65 0.02 0.00 65.93 65.93 0.32 |
| 3405 | ....... |
| 3406 | 83 DBAR -1 159 9 84 95 66 0.07 0.00 27.33 27.33 0.32 |
| 3407 | 84 DQRK 1 159 9 46 104 83 0.23 0.00 11.57 11.58 0.32 |
| 3408 | |
| 3409 | ---CLUSTER FORMATION--- |
| 3410 | |
| 3411 | Next the clusters themselves are listed. The mothers of a cluster are |
| 3412 | the partons from which it is made, and the daughters are the primary |
| 3413 | hadrons into which it decays. |
| 3414 | |
| 3415 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3416 | 85 CLUS 91 184 45 65 105 106 0.07 0.00 310.56 310.56 1.23 |
| 3417 | 86 CLUS 91 183 47 69 107 108 4.40 -0.09 69.69 69.85 1.59 |
| 3418 | ....... |
| 3419 | 103 CLUS 91 183 82 79 139 140 -5.81 -3.42 2.54 7.49 2.06 |
| 3420 | 104 CLUS 91 183 84 46 141 142 2.13 0.01 45.01 45.08 1.04 |
| 3421 | |
| 3422 | ---CLUSTER DECAYS--- |
| 3423 | |
| 3424 | The clusters, including the b-flavoured clusters 94 and 101, now |
| 3425 | decay, usually into pairs of hadrons chosen according to the density |
| 3426 | of states. Sometimes single-hadron decays occur, with transfer of |
| 3427 | momentum to a neighbouring cluster, if there is insufficient phase |
| 3428 | space for two-body decay. Note that cluster 94 actually did a 1-body |
| 3429 | decay into a B- (IHEP=123, ISTHEP=196). Hadrons with ISTHEP=1 are |
| 3430 | stable. ISTHEP=200 indicates a neutral B meson which may undergo |
| 3431 | flavour oscillation. |
| 3432 | |
| 3433 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3434 | 105 PBAR -2212 1 85 9 0 0 -0.13 0.09 215.09 215.09 0.94 |
| 3435 | 106 PI+ 211 1 85 9 0 0 0.20 -0.09 95.47 95.47 0.14 |
| 3436 | 107 OMEGA 223 197 86 9 143 145 2.33 -0.03 34.12 34.20 0.78 |
| 3437 | 108 RHO+ 213 197 86 9 146 147 2.07 -0.06 35.58 35.65 0.77 |
| 3438 | ....... |
| 3439 | 123 B- -521 196 94 43 163 165 -25.44 -14.98 11.97 32.29 5.28 |
| 3440 | ....... |
| 3441 | 136 B_S0 531 200 101 32 176 176 14.56 -33.17 -4.60 36.91 5.38 |
| 3442 | ....... |
| 3443 | 141 PI0 111 1 104 9 0 0 0.66 0.06 16.64 16.65 0.14 |
| 3444 | 142 RHO- -213 197 104 9 185 186 1.47 -0.05 28.37 28.42 0.77 |
| 3445 | |
| 3446 | ---STRONG HADRON DECAYS--- |
| 3447 | |
| 3448 | The unstable hadrons decay according to decay tables. Remember that |
| 3449 | the pi0 was set stable in the initialization phase. For heavy (b,c) |
| 3450 | quarks, partonic or direct hadronic decays may occur. In this event |
| 3451 | the B- does a b -> u directly to rho0 e- nu_ebar. The B_s oscillates |
| 3452 | into a B_sbar which decays partonically to c cbar s sbar. |
| 3453 | |
| 3454 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3455 | 143 PI+ 211 1 107 9 0 0 1.90 -0.02 24.27 24.35 0.14 |
| 3456 | 144 PI- -211 1 107 9 0 0 0.32 0.00 6.77 6.78 0.14 |
| 3457 | 145 PI0 111 1 107 9 0 0 0.11 -0.02 3.07 3.08 0.14 |
| 3458 | 146 PI+ 211 1 108 9 0 0 1.80 0.19 29.01 29.07 0.14 |
| 3459 | 147 PI0 111 1 108 9 0 0 0.27 -0.25 6.57 6.58 0.14 |
| 3460 | ....... |
| 3461 | 163 RHO0 113 198 123 43 194 195 -18.44 -9.34 6.79 21.77 0.77 |
| 3462 | 164 E- 11 1 123 43 0 0 -6.49 -5.26 5.27 9.88 0.00 |
| 3463 | 165 NU_EBAR -12 1 123 43 0 0 -0.50 -0.38 -0.09 0.63 0.00 |
| 3464 | ....... |
| 3465 | 176 B_SBAR0 -531 199 136 32 207 208 14.56 -33.17 -4.60 36.91 5.38 |
| 3466 | 205 PI0 111 1 187 9 0 0 0.51 -0.06 1.56 1.65 0.14 |
| 3467 | 206 PI0 111 1 187 9 0 0 0.14 0.12 1.63 1.64 0.14 |
| 3468 | |
| 3469 | ---HEAVY FLAVOUR DECAYS--- |
| 3470 | |
| 3471 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3472 | 207 BQRK 5 155 176 208 209 211 13.20 -30.08 -4.17 33.47 4.88 |
| 3473 | 208 SBAR -3 125 176 211 212 211 1.35 -3.09 -0.43 3.43 0.50 |
| 3474 | 209 CQRK 4 123 207 210 213 210 2.30 -5.94 -0.61 6.59 1.55 |
| 3475 | 210 CBAR -4 124 207 209 215 209 3.58 -8.37 -1.74 9.40 1.55 |
| 3476 | 211 SQRK 3 124 207 207 217 207 7.33 -15.77 -1.82 17.49 0.50 |
| 3477 | 212 SBAR -3 160 208 221 223 221 1.35 -3.09 -0.43 3.43 0.50 |
| 3478 | |
| 3479 | The B_sbar decay products hadronize to eta_c K+ K-: |
| 3480 | |
| 3481 | ---CLUSTER DECAYS--- |
| 3482 | |
| 3483 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3484 | 224 ETA_C 441 199 222 213 227 229 4.87 -12.18 -2.12 13.62 2.98 |
| 3485 | 225 K- -321 1 223 217 0 0 8.22 -17.67 -2.03 19.60 0.49 |
| 3486 | 226 K+ 321 1 223 217 0 0 1.47 -3.31 -0.45 3.69 0.49 |
| 3487 | |
| 3488 | The eta_c decays partonically to 3 gluons: |
| 3489 | |
| 3490 | ---HEAVY FLAVOUR DECAYS--- |
| 3491 | |
| 3492 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3493 | 227 GLUON 21 123 224 229 230 228 2.59 -4.45 -1.11 5.32 0.75 |
| 3494 | 228 GLUON 21 124 224 227 232 229 0.84 -4.20 -0.51 4.38 0.75 |
| 3495 | 229 GLUON 21 124 224 228 234 227 1.44 -3.53 -0.50 3.92 0.75 |
| 3496 | |
| 3497 | Finally the 3 gluons hadronize to pi+ pi- 4 pi0: |
| 3498 | |
| 3499 | ---CLUSTER DECAYS--- |
| 3500 | |
| 3501 | IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS |
| 3502 | 245 PI- -211 1 242 230 0 0 1.53 -3.79 -0.46 4.11 0.14 |
| 3503 | 246 PI0 111 1 242 230 0 0 0.06 -0.12 -0.07 0.20 0.14 |
| 3504 | 247 PI0 111 1 243 232 0 0 0.52 -0.39 0.03 0.66 0.14 |
| 3505 | 248 PI0 111 1 243 232 0 0 1.30 -3.27 -1.01 3.66 0.14 |
| 3506 | 249 PI0 111 1 244 234 0 0 1.02 -3.98 -0.74 4.18 0.14 |
| 3507 | 250 PI+ 211 1 244 234 0 0 0.43 -0.64 0.14 0.80 0.14 |
| 3508 | |
| 3509 | After the 1000 events requested have been generated, an analysis of |
| 3510 | the associated weight distribution and cross section is printed. |
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