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Commit | Line | Data |
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cb220f83 | 1 | |
2 | ------------------------------------------------------------- | |
3 | HYDJET, fast MC code to simulate flow effects, jet production | |
4 | and jet quenching in heavy ion AA collisions at the LHC | |
5 | ------------------------------------------------------------- | |
6 | This code is merging HYDRO (flow effects), PYTHIA6.4 (hard jet | |
7 | production) and PYQUEN (jet quenching) | |
8 | -------------------------------------------------------------- | |
9 | ||
10 | Igor Lokhtin, SINP MSU, Moscow, RU | |
11 | e-mail: Igor.Lokhtin@cern.ch | |
12 | ||
13 | Reference for HYDJET: | |
14 | I.P. Lokhtin, A.M. Snigirev, | |
15 | Eur. Phys. J. C 46 (2006) 211. | |
16 | ||
17 | References for HYDRO: | |
18 | N.A.Kruglov, I.P.Lokhtin, L.I.Sarycheva, A.M.Snigirev, | |
19 | Z. Phys. C 76 (1997) 99; | |
20 | I.P.Lokhtin, L.I.Sarycheva, A.M.Snigirev, | |
21 | Phys. Lett. B 537 (2002) 261; | |
22 | I.P.Lokhtin, A.M.Snigirev, Preprint SINP MSU 2004-14/753, hep-ph/0312204. | |
23 | ||
24 | References for PYQUEN: | |
25 | I.P.Lokhtin, A.M.Snigirev, Eur.Phys.J. C16 (2000) 527; | |
26 | I.P.Lokhtin, A.M.Snigirev, Preprint SINP MSU 2004-13/752, hep-ph/0406038. | |
27 | ||
28 | References for PYTHIA: | |
29 | T.Sjostrand et al., Comput.Phys.Commun. 135 (2001) 238; | |
30 | T.Sjostrand, S. Mrena and P. Skands, hep-ph/0603175. | |
31 | ||
32 | Reference for JETSET event format: | |
33 | T.Sjostrand, Comput.Phys.Commun. 82 (1994) 74. | |
34 | ||
35 | -------------------------------------------------------------- | |
36 | Web-page: | |
37 | http://cern.ch/lokhtin/hydro | |
38 | -------------------------------------------------------------- | |
39 | ||
40 | Description of routine | |
41 | ||
42 | CALL hydro(A,ifb,bmin,bmax,bfix,nh) - generates one event | |
43 | ||
44 | input parameters to fix event configuration : | |
45 | (set in main user routine before hydro call) | |
46 | ||
47 | A - beam and target nucleus atomic weight | |
48 | ifb - flag of type of centrality generation | |
49 | =0 impact parameter is fixed (bfix) | |
50 | >0 or <0 impact parameter is generated with standard Glauber geometry | |
51 | between minimum (bmin) and maximum (bmax) values | |
52 | bmin - minimum impact parameter in units of nucleus radius RA | |
53 | (i.e. minimum value in [fm] will be bmin*RA), | |
54 | valid only if ifb not equal to zero | |
55 | bmax - maximum impact parameter in units of nucleus radius RA | |
56 | (i.e. maximum value in [fm] will be bmax*RA), | |
57 | valid only if ifb not equal to zero | |
58 | bfix - fixed impact parameter in units of nucleus radius RA | |
59 | (i.e. fixed value in [fm] will be bfix*RA), | |
60 | valid only if ifb=0 | |
61 | nh - mean soft hadron multiplicity in central Pb-Pb collisions | |
62 | (multiplicity for other centralities and atomic numbers | |
63 | will be calculated automatically). | |
64 | ||
65 | -------------------------------------------------------------- | |
66 | ||
67 | Parameters in COMMON BLOCKS which can be varied by user: | |
68 | ||
69 | COMMON /hyflow/ ytfl,ylfl,fpart | |
70 | ytfl - maximum transverse collective rapidity, controls slope of low-pt spectra | |
71 | (allowed range is 0.01<ytfl<3.0, default value is ytfl=1.). | |
72 | ylfl - maximum longitudinal collective rapidity, controls width of eta-spectra | |
73 | (allowed range is 0.01<ylfl<7.0, default value is ylfl=5.). | |
74 | fpart - fraction of soft multiplicity proportional to the number of nucleon | |
75 | participants; then (1.-fpart) will be the fraction of soft multiplicity | |
76 | proportional to the number of nucleon-nucleon binary sub-collisions | |
77 | (allowed range is 0.01<fpart<1.0, default value is fpart=1.). | |
78 | ||
79 | COMMON /hyjpar/ nhsel,ptmin,njet | |
80 | nhsel - flag to include jet production in hydro event: | |
81 | nhsel=0 - jet production off (pure HYDRO event); | |
82 | nhsel=1 - jet production on, jet quenching off (HYDRO+njet*PYTHIA events); | |
83 | nhsel=2 - jet production & jet quenching on (HYDRO+njet*PYQUEN events); | |
84 | nhsel=3 - jet production on, jet quenching off, HYDRO off (njet*PYTHIA events); | |
85 | nhsel=4 - jet production & jet quenching on, HYDRO off (njet*PYQUEN events); | |
86 | (default value is nhsel = 0). | |
87 | ptmin - minimal pt of parton-parton scattering in PYTHIA event, parameter | |
88 | ckin(3) in PYTHIA common block /pysubs/ should be set equal to ptmin | |
89 | (allowed range is 5 GeV < ptmin < 500 GeV, default value ptmin=10 GeV). | |
90 | ||
91 | -------------------------------------------------------------- | |
92 | ||
93 | Output event parameters in COMMON BLOCKS: | |
94 | ||
95 | COMMON /hyjpar/ nhsel,ptmin,njet | |
96 | njet - number of hard parton-parton scatterings with pt>ptmin in event. | |
97 | ||
98 | common /hyfpar/ bgen,nbcol,npart,npyt,nhyd | |
99 | bgen - generated value of impact parameter in units of nucleus radius RA | |
100 | (i.e the value in [fm] will be bgen*RA). | |
101 | nbcol - mean number of nucleon-nucleon binary sub-collisions at given 'bgen'. | |
102 | npart - mean number of nucleon participants at given 'bgen'. | |
103 | npyt - multiplicity of hard PYTHIA/PYQUEN-induced particles in event | |
104 | (including full parton story). | |
105 | nhyd - multiplicity of soft HYDRO-induced hadrons in event. | |
106 | ||
107 | -------------------------------------------------------------- | |
108 | ||
109 | Output particle information | |
110 | ||
111 | COMMON /lujets/ n,k(150000,5),p(150000,5),v(150000,5) | |
112 | n - total event multiplicity | |
113 | k(i,1-5) - particle codes | |
114 | p(i,1-5) - particle four-momentum and mass | |
115 | v(i,1-5) - particle vertex, production time and lifetime | |
116 | ||
117 | NOTE! First 'npyt' lines in event list correspond to PYTHIA/PYQUEN-induced | |
118 | particles, last 'nhyd' lines -- HYDRO-induced hadrons. | |
119 | ||
120 | COMMON /hyjets/ nl,kl(150000,5),pl(150000,5),vl(150000,5) | |
121 | contains list of parton history of event in the same format as /lujets/ | |
122 | ||
123 | -------------------------------------------------------------- | |
124 | ||
125 | NOTE! Main users routine should be compiled with object files obtained by: | |
126 | - jetset_73.f with extended array size in common block /lujets/; | |
127 | - pythia6.401.f (or later versions); | |
128 | - pyquen1_1.f; | |
129 | - hydjet1_1.f. | |
130 | ||
131 | NOTE! Since variables (A-H, O-Z) are described as IMPLICIT DOUBLE PRECISION | |
132 | in 'pythia' and 'pyquen', the corresponding 'pythia' and 'pyquen' variables and | |
133 | parameters used in main users routine should be described also as 'double | |
134 | precision'. However variables and parameters from JETSET and HYDRO including | |
135 | output event information are supposed to be REAL. | |
136 | ||
137 | NOTE! Since pyquen deals with partonic pythia event, the fragmentation in | |
138 | subroutine 'hyhard' is switched off before pyquen call using parameter | |
139 | mstp(111) from pythia common block pypars: | |
140 | ... | |
141 | mstp(111)=0 ! fragmentation off | |
142 | c mstj(41)=0 ! vacuum showering off | |
143 | call pyevnt ! 'normal' single pythia event | |
144 | ... | |
145 | call pyquen(A,ifb,bfix) ! 'quenched' single pythia event | |
146 | ... | |
147 | call pyexec ! fragmentation done | |
148 | ... | |
149 | in the case if Pythia final state radiation is switching off (if one set | |
150 | mstj(41)=0 in 'hyhard'), the Pyquen option "vacuum showering after | |
151 | in-medium partonic energy loss" is foreseen. | |
152 | ||
153 | NOTE! In order to adjust string fragmentation with additional gluons in Pythia, | |
154 | the parameter paru(14)=1.d0 have to be specified in main users routine. | |
155 | ||
156 | ------------------------------------------------------------------------- | |
157 | ||
158 | Physics validity of the model | |
159 | ||
160 | 1. Internal parameters of the routine were optimized as an estimation | |
161 | for LHC heavy ion beam energies. The result for other beam energy ranges, | |
162 | obtained without additional internal parameters adjusting, is not expected | |
163 | to be reasonable. | |
164 | 2. Hydro-type approximation for heavy ion collisions is expected to be | |
165 | applicable for central and semi-central collisions. The result obtained for | |
166 | very peripheral collisions (b~2*RA) can be not adequate. | |
167 | 3. We do not expect correct event description for very forward rapidities | |
168 | (|y|>3), where other mechanisms of particle production among hydro-flow and | |
169 | jets can be important. |