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[u/mrichter/AliRoot.git] / EVGEN / AliGenPMDlib.cxx
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0ed0a0a2 1/**************************************************************************
2 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
3 * *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
6 * *
7 * Permission to use, copy, modify and distribute this software and its *
8 * documentation strictly for non-commercial purposes is hereby granted *
9 * without fee, provided that the above copyright notice appears in all *
10 * copies and that both the copyright notice and this permission notice *
11 * appear in the supporting documentation. The authors make no claims *
12 * about the suitability of this software for any purpose. It is *
13 * provided "as is" without express or implied warranty. *
14 **************************************************************************/
15
88cb7938 16/* $Id$ */
0ed0a0a2 17
ac3faee4 18//
19// Library of generators for PMD
20// providing y and pt parametrisation
21// for generated tracks
22// Specific for PMD needs
23// Author: PMD Offline Group
24//
25
116cbefd 26#include <TMath.h>
27#include <TPDGCode.h>
28
0ed0a0a2 29#include "AliGenPMDlib.h"
0ed0a0a2 30
31ClassImp(AliGenPMDlib)
32//
33// Neutral Pions
34
75e0cc59 35Double_t AliGenPMDlib::PtPi0(const Double_t *px, const Double_t */*dummy*/)
0ed0a0a2 36{
37//
38// PT-PARAMETERIZATION CDF, PRL 61(88) 1819
39// POWER LAW FOR PT > 500 MEV
40// MT SCALING BELOW (T=160 MEV)
41//
42 const Double_t kp0 = 1.3;
43 const Double_t kxn = 8.28;
44 const Double_t kxlim=0.5;
45 const Double_t kt=0.160;
46 const Double_t kxmpi=0.139;
47 const Double_t kb=1.;
48 Double_t y, y1, xmpi2, ynorm, a;
49 Double_t x=*px;
50 //
51 y1=TMath::Power(kp0/(kp0+kxlim),kxn);
52 xmpi2=kxmpi*kxmpi;
53 ynorm=kb*(TMath::Exp(-sqrt(kxlim*kxlim+xmpi2)/kt));
54 a=ynorm/y1;
55 if (x > kxlim)
56 y=a*TMath::Power(kp0/(kp0+x),kxn);
57 else
58 y=kb*TMath::Exp(-sqrt(x*x+xmpi2)/kt);
59 return y*x;
60}
61
62//
63// y-distribution
64//
75e0cc59 65Double_t AliGenPMDlib::YPi0( const Double_t *py, const Double_t */*dummy*/)
0ed0a0a2 66{
67 //
68 // y parametrisation for pi0
69 //
70 const Double_t ka1 = 4913.;
71 const Double_t ka2 = 1819.;
72 const Double_t keta1 = 0.22;
73 const Double_t keta2 = 3.66;
74 const Double_t kdeta1 = 1.47;
75 const Double_t kdeta2 = 1.51;
76 Double_t y=TMath::Abs(*py);
77 //
78 Double_t ex1 = (y-keta1)*(y-keta1)/(2*kdeta1*kdeta1);
79 Double_t ex2 = (y-keta2)*(y-keta2)/(2*kdeta2*kdeta2);
80 return ka1*TMath::Exp(-ex1)+ka2*TMath::Exp(-ex2);
81}
82
83// particle composition
84//
65fb704d 85Int_t AliGenPMDlib::IpPi0(TRandom *)
0ed0a0a2 86{
87// Pi0
88 return kPi0;
89}
90
91//____________________________________________________________
92//
93// Mt-scaling
94
95Double_t AliGenPMDlib::PtScal(Double_t pt, Int_t np)
96{
97 // SCALING EN MASSE PAR RAPPORT A PTPI
98 // MASS PI,K,ETA,RHO,OMEGA,ETA',PHI
99 const Double_t khm[10] = {.13957,.493,.5488,.769,.7826,.958,1.02,0,0,0};
100 // VALUE MESON/PI AT 5 GEV
101 const Double_t kfmax[10]={1.,0.3,0.55,1.0,1.0,1.0,1.0,0,0,0};
102 np--;
103 Double_t f5=TMath::Power(((sqrt(100.018215)+2.)/(sqrt(100.+khm[np]*khm[np])+2.0)),12.3);
104 Double_t fmax2=f5/kfmax[np];
105 // PIONS
106 Double_t ptpion=100.*PtPi0(&pt, (Double_t*) 0);
107 Double_t fmtscal=TMath::Power(((sqrt(pt*pt+0.018215)+2.)/
108 (sqrt(pt*pt+khm[np]*khm[np])+2.0)),12.3)/ fmax2;
109 return fmtscal*ptpion;
110}
111//
112// kaon
113//
114// pt-distribution
115//____________________________________________________________
116
75e0cc59 117Double_t AliGenPMDlib::PtEta( const Double_t *px, const Double_t */*dummy*/)
0ed0a0a2 118{
119// Kaon pT
120 return PtScal(*px,3);
121}
122
123// y-distribution
124//____________________________________________________________
75e0cc59 125Double_t AliGenPMDlib::YEta( const Double_t *py, const Double_t */*dummy*/)
0ed0a0a2 126{
127 //
128 // y parametrisation for etas
129 //
130 const Double_t ka1 = 4913.;
131 const Double_t ka2 = 1819.;
132 const Double_t keta1 = 0.22;
133 const Double_t keta2 = 3.66;
134 const Double_t kdeta1 = 1.47;
135 const Double_t kdeta2 = 1.51;
136 Double_t y=TMath::Abs(*py);
137 //
138 Double_t ex1 = (y-keta1)*(y-keta1)/(2*kdeta1*kdeta1);
139 Double_t ex2 = (y-keta2)*(y-keta2)/(2*kdeta2*kdeta2);
140 return ka1*TMath::Exp(-ex1)+ka2*TMath::Exp(-ex2);
141}
142
143// particle composition
144//
65fb704d 145Int_t AliGenPMDlib::IpEta(TRandom *)
0ed0a0a2 146{
147 return 221;
148}
149
150
75e0cc59 151typedef Double_t (*GenFunc) (const Double_t*, const Double_t*);
198bb1c7 152GenFunc AliGenPMDlib::GetPt(Int_t param, const char* /*tname*/) const
0ed0a0a2 153{
154// Return pointer to pT parameterisation
155 GenFunc func=NULL;
156 switch (param)
157 {
34f60c01 158 case kPion:
0ed0a0a2 159 func=PtPi0;
160 break;
34f60c01 161 case kEta:
0ed0a0a2 162 func=PtEta;
163 break;
164 default:
165 func=0;
166 printf("<AliGenPMDlib::GetPt> unknown parametrisation\n");
167 }
168 return func;
169}
170
198bb1c7 171GenFunc AliGenPMDlib::GetY(Int_t param, const char* /*tname*/) const
0ed0a0a2 172{
173// Return pointer to y- parameterisation
174 GenFunc func=NULL;
175 switch (param)
176 {
34f60c01 177 case kPion:
0ed0a0a2 178 func=YPi0;
179 break;
34f60c01 180 case kEta:
0ed0a0a2 181 func=YEta;
182 break;
183 default:
184 func=0;
185 printf("<AliGenPMDlib::GetY> unknown parametrisation\n");
186 }
187 return func;
188
189}
65fb704d 190typedef Int_t (*GenFuncIp) (TRandom *);
198bb1c7 191GenFuncIp AliGenPMDlib::GetIp(Int_t param, const char* /*tname*/) const
0ed0a0a2 192{
193// Return pointer to particle type parameterisation
194 GenFuncIp func=NULL;
195 switch (param)
196 {
34f60c01 197 case kPion:
0ed0a0a2 198 func=IpPi0;
199 break;
34f60c01 200 case kEta:
0ed0a0a2 201 func=IpEta;
202 break;
203 default:
204 printf("<AliGenPMDlib::GetIp> unknown parametrisation\n");
205 }
206 return func;
207}
208
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211