restore threshold getters after parameter dynamics update (fw v. >= A012)
[u/mrichter/AliRoot.git] / HERWIG / herwig59.txt
CommitLineData
d909f169 1CDECK 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------------------------------------------------------------------------
13with Deep Inelastic Scattering and Heavy Flavour Electroproduction by
14G.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
972C---COMMON BLOCKS ARE INCLUDED AS FILE HERWIG59.INC
973 INCLUDE 'HERWIG59.INC'
974 INTEGER N
975C---MAX NUMBER OF EVENTS THIS RUN
976 MAXEV=100
977C---BEAM PARTICLES
978 PART1='PBAR'
979 PART2='P'
980C---BEAM MOMENTA
981 PBEAM1=900.
982 PBEAM2=900.
983C---PROCESS
984 IPROC=1500
985C---INITIALISE OTHER COMMON BLOCKS
986 CALL HWIGIN
987C---USER CAN RESET PARAMETERS AT
988C THIS POINT, OTHERWISE DEFAULT
989C VALUES IN HWIGIN WILL BE USED.
990 PTMIN=100.
991C---COMPUTE PARAMETER-DEPENDENT CONSTANTS
992 CALL HWUINC
993C---CALL HWUSTA TO MAKE ANY PARTICLE STABLE
994 CALL HWUSTA('PI0 ')
995C---USER'S INITIAL CALCULATIONS
996 CALL HWABEG
997C---INITIALISE ELEMENTARY PROCESS
998 CALL HWEINI
999C---LOOP OVER EVENTS
1000 DO 100 N=1,MAXEV
1001C---INITIALISE EVENT
1002 CALL HWUINE
1003C---GENERATE HARD SUBPROCESS
1004 CALL HWEPRO
1005C---GENERATE PARTON CASCADES
1006 CALL HWBGEN
1007C---DO HEAVY QUARK DECAYS
1008 CALL HWDHQK
1009C---DO CLUSTER FORMATION
1010 CALL HWCFOR
1011C---DO CLUSTER DECAYS
1012 CALL HWCDEC
1013C---DO UNSTABLE PARTICLE DECAYS
1014 CALL HWDHAD
1015C---DO HEAVY FLAVOUR HADRON DECAYS
1016 CALL HWDHVY
1017C---ADD SOFT UNDERLYING EVENT IF NEEDED
1018 CALL HWMEVT
1019C---FINISH EVENT
1020 CALL HWUFNE
1021C---USER'S EVENT ANALYSIS
1022 CALL HWANAL
1023 100 CONTINUE
1024C---TERMINATE ELEMENTARY PROCESS
1025 CALL HWEFIN
1026C---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
1740C ****COMMON BLOCK FILE FOR HERWIG VERSION 5.9****
1741C
1742C ALTERATIONS: See 5.8 for list of previous revisions
1743C Layout completely overhauled
1744C
1745C The following variables have been removed:
1746C FBTM,FTOP,FHVY,VECWT,TENWT,SWT,RESWT
1747C MADDR,MODES,MODEF,IDPRO
1748C The following COMMON BLOCK has been removed
1749C /HWUFHV/ - BDECAY moved to /HWPRCH/
1750C The following COMMON BLOCKs have been added
1751C /HWBMCH/ -contains PART1, PART2 from /HWBEAM/
1752C /HWPRCH/ -contains AUTPDF from /HWPARM/ & BDECAY
1753C /HWPROP/ -contains many variables from /HWUPDT/
1754C /HWDIST/ -contains variables for mixing and vertices
1755C /HWQDKS/ -contains heavy flavour decay information
1756C The following variables have been changed to CHARACTER*8:
1757C PART1,PART2,RNAME
1758C The following parameters have been added:
1759C NMXCDK,NMXDKS,NMXMOD,NMXQDK,NMXRES
1760C The following variables have been added:
1761C CSPEED,F0MIX,F1MIX,F2MIX,H1MIX,
1762C PHIMIX,IOPREM,PRVTX see HWPRAM
1763C ANOMSC,ISLENT see HWBRCH
1764C GAMWT see HWEVNT
1765C ASFIXD,OMEGA0,TMNISR,WHMIN,YWWMAX,
1766C YWWMIN,ZMXISR,COLISR see HWHARD
1767C IFLAV,RLTIM,RSPIN,VTOCDK,VTORDK see HWPROP
1768C DKLTM,IDK,IDKPRD,LNEXT,LSTRT,
1769C NDKYS,NME,NMODES,NPRODS,
1770C DKPSET,RSTAB see HWUPDT
1771C REPWT,SNGWT see HWUWTS
1772C CLDKWT,CTHRPW,PRECO,NCLDK,CLRECO see HWUCLU
1773C EXAG,GEV2MM,HBAR,PLTCUT,VMIN2,
1774C VTXPIP,XMIX,XMRCT,YMIX,YMRCT,
1775C IOPDKL,MAXDKL,MIXING,PIPSMR see HWDIST
1776C VTXQDK,IMQDK,LOCQ,NQDK see HWQDKS
1777C
1778C
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)
1783C
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
1800C
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
1812C
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
1818C
1819 CHARACTER*4
1820 & BDECAY
1821 CHARACTER*8
1822 & PART1,PART2,RNAME
1823 CHARACTER*20
1824 & AUTPDF
1825C
1826C 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)
1830C
1831C 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
1835C
1836C 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
1845C
1846 COMMON/HWPRCH/AUTPDF(2),BDECAY
1847C
1848C 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)
1852C
1853C Parton polarization common
1854 COMMON/HWPARP/DECPAR(2,NMXPAR),PHIPAR(2,NMXPAR),RHOPAR(2,NMXPAR),
1855 & TMPAR(NMXPAR)
1856C
1857C Electroweak boson common
1858 PARAMETER (MODMAX=5)
1859 COMMON/HWBOSC/ALPFAC,BRHIG(12),ENHANC(12),GAMMAX,RHOHEP(3,NMXHEP),
1860 & IOPHIG,MODBOS(MODMAX)
1861C
1862C Parton colour common
1863 COMMON/HWPARC/JCOPAR(4,NMXPAR)
1864C
1865C 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
1868C
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
1872C
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
1880C
1881C 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)
1886C
1887 COMMON/HWUNAM/RNAME(0:NMXRES)
1888C
1889C Arrays for particle decays (NMXDKS = max total no of decays,
1890C 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)
1895C
1896C Weights used in cluster decays
1897 COMMON/HWUWTS/REPWT(0:3,0:4,0:4),SNGWT,DECWT,QWT(3),PWT(12),
1898 & SWTEF(NMXRES)
1899C
1900C Parameters for cluster decays (NMXCDK = max total no of cluster
1901C 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
1905C
1906C 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
1909C
1910C Arrays for temporarily storing heavy-b,c-hadrons decaying partonicaly
1911C (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
1914C
1915C Parameters for Sudakov form factors
1916C (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
1920C
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
2773Line, 565 decay: LMBDA_C+ --> XI*0 K*+
2774is kinematically not allowed, Min-Mout= -0.139
2775LMBDA_C+: BR sum = 0.97800
2776Rescaling to 1
2777
2778Line, 990 decay: LMBDA_C- --> XI*BAR K*-
2779is kinematically not allowed, Min-Mout= -0.139
2780LMBDA_C-: BR sum = 0.97800
2781Rescaling 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
3193Line, 565 decay: LMBDA_C+ --> XI*0 K*+
3194is kinematically not allowed, Min-Mout= -0.139
3195LMBDA_C+: BR sum = 0.97800
3196Rescaling to 1
3197
3198Line, 990 decay: LMBDA_C- --> XI*BAR K*-
3199is kinematically not allowed, Min-Mout= -0.139
3200LMBDA_C-: BR sum = 0.97800
3201Rescaling 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
3232EVENT 39: 900.00 GEV/C PBAR ON 900.00 GEV/C P PROCESS: 11706
3233
3234SEEDS: 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.