newly implemented model for slow nucleon production
[u/mrichter/AliRoot.git] / EVGEN / AliSlowNucleonModelExp.cxx
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c9a8628a 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
803d1ab0 16/* $Id$ */
c9a8628a 17
c9a8628a 18//
ac3faee4 19// Experimental data inspired Gray Particle Model for p-Pb collisions
c9a8628a 20// The number of gray nucleons is proportional to the number of collisions.
21// The number of black nucleons is proportional to the number of collisions
22// Fluctuations are calculated from a binomial distribution.
ac3faee4 23// Author: A.Morsch
c9a8628a 24//
25
26#include "AliSlowNucleonModelExp.h"
27#include "AliCollisionGeometry.h"
28#include <TRandom.h>
58776b75 29#include <TMath.h>
c9a8628a 30
706938e6 31ClassImp(AliSlowNucleonModelExp)
c9a8628a 32
1c56e311 33
34AliSlowNucleonModelExp::AliSlowNucleonModelExp():
35 fP(82),
58776b75 36 fN (126),
1ffc7bfa 37 fAlphaGray(2.3),
38 fAlphaBlack(3.6),
230d85c6 39 fApplySaturation(kTRUE),
40 fnGraySaturation(15),
41 fnBlackSaturation(28)
c9a8628a 42{
ac3faee4 43 //
44 // Default constructor
45 //
1ffc7bfa 46 //
47 printf("\n\nInitializing slow nucleon model with parameters:\n");
48 printf(" \t alpha_{gray} %1.2f alpha_{black} %1.2f\n",fAlphaGray, fAlphaBlack);
58776b75 49 //printf(" \t SATURATION %d w. %d (gray) %d (black) \n\n",fApplySaturation,fnGraySaturation,fnBlackSaturation);
c9a8628a 50}
51
52
53void AliSlowNucleonModelExp::GetNumberOfSlowNucleons(AliCollisionGeometry* geo,
ac3faee4 54 Int_t& ngp, Int_t& ngn, Int_t & nbp, Int_t & nbn) const
c9a8628a 55{
56//
57// Return the number of black and gray nucleons
58//
59// Number of collisions
60
58776b75 61 Float_t nu = geo->NN() + geo->NwN() + geo->NNw();
c9a8628a 62
63// Mean number of gray nucleons
64
65 Float_t nGray = fAlphaGray * nu;
66 Float_t nGrayNeutrons = nGray * fN / (fN + fP);
67 Float_t nGrayProtons = nGray - nGrayNeutrons;
68
69// Mean number of black nucleons
230d85c6 70 Float_t nBlack = 0.;
71 if(!fApplySaturation || (fApplySaturation && nGray<fnGraySaturation)) nBlack = fAlphaBlack * nu;
72 else if(fApplySaturation && nGray>=fnGraySaturation) nBlack = fnBlackSaturation;
1ffc7bfa 73 Float_t nBlackNeutrons = nBlack * 0.84;
c9a8628a 74 Float_t nBlackProtons = nBlack - nBlackNeutrons;
75
76// Actual number (including fluctuations) from binomial distribution
77 Double_t p;
78
79// gray neutrons
80 p = nGrayNeutrons/fN;
81 ngn = gRandom->Binomial((Int_t) fN, p);
82
83// gray protons
84 p = nGrayProtons/fP;
85 ngp = gRandom->Binomial((Int_t) fP, p);
86
87// black neutrons
88 p = nBlackNeutrons/fN;
89 nbn = gRandom->Binomial((Int_t) fN, p);
90
91// black protons
92 p = nBlackProtons/fP;
93 nbp = gRandom->Binomial((Int_t) fP, p);
58776b75 94
95}
96
97void AliSlowNucleonModelExp::GetNumberOfSlowNucleons2(AliCollisionGeometry* geo,
98 Int_t& ngp, Int_t& ngn, Int_t & nbp, Int_t & nbn) const
99{
100//
101// Return the number of black and gray nucleons
102//
103// Number of collisions
104
105 // based on E910 model ================================================================
106
107 Float_t nu = (Float_t) (geo->NN() + geo->NwN() + geo->NNw());
108 //
109 nu = nu+1.*gRandom->Rndm();
110 //
111 Float_t poverpd = 0.843;
112 Float_t zAu2zPb = 82./79.;
113 Float_t nGrayp = (-0.27 + 0.63 * nu - 0.0008 *nu *nu)*poverpd*zAu2zPb;
114
115// gray protons
116 Double_t p;
117 p = nGrayp/fP;
118 ngp = gRandom->Binomial((Int_t) fP, p);
119 //ngp = gRandom->Gaus(nGrayp, TMath::Sqrt(fP*p*(1-p)));
120 if(nGrayp<0.) ngp=0;
121
122 //Float_t blackovergray = 3./7.;// from spallation
123 Float_t blackovergray = 0.65; // from COSY
124 Float_t nBlackp = blackovergray*nGrayp;
125
126// black protons
127 p = nBlackp/fP;
128 nbp = gRandom->Binomial((Int_t) fP, p);
129 //nbp = gRandom->Gaus(nBlackp, TMath::Sqrt(fP*p*(1-p)));
130 if(nBlackp<0.) nbp=0;
131
132 if(nu<3.){
133 nGrayp = -0.836 + 0.9112 *nu - 0.05381 *nu *nu;
134 nBlackp = blackovergray*nGrayp;
135 }
136
137 Float_t nGrayNeutrons = 0.;
138 Float_t nBlackNeutrons = 0.;
139 Float_t cp = (nGrayp+nBlackp)/0.24;
140
141 if(cp>0.){
142 Float_t nSlow = 51.5+469.2/(-8.762-cp);
143 //if(cp<2.5) nSlow = 1+(9.9-1)/(2.5-0)*(cp-0);
144 if(cp<3.) nSlow = 0.+(11.6-0.)/(3.-0.)*(cp-0.);
145
146 nGrayNeutrons = nSlow * 0.1;
147 nBlackNeutrons = nSlow - nGrayNeutrons;
148 }
149 else{
150 // Sikler "pasturato"
151 nGrayNeutrons = 0.47 * fAlphaGray * nu;
152 nBlackNeutrons = 0.88 * fAlphaBlack * nu;
153 printf("nslowp=0 -> ncoll = %1.0f -> ngrayn = %1.0f nblackn = %1.0f \n", nu, nGrayNeutrons, nBlackNeutrons);
154 }
155
156// gray neutrons
157 p = nGrayNeutrons/fN;
158// ngn = gRandom->Binomial((Int_t) fN, p);
159 ngn = gRandom->Gaus(nGrayNeutrons, TMath::Sqrt(fN*p*(1-p)));
160
161// black neutrons
162 p = nBlackNeutrons/fN;
163// nbn = gRandom->Binomial((Int_t) fN, p);
164 nbn = gRandom->Gaus(nBlackNeutrons, TMath::Sqrt(fN*p*(1-p)));
165
166
c9a8628a 167}
168
169void AliSlowNucleonModelExp::SetParameters(Float_t alpha1, Float_t alpha2)
170{
171 // Set the model parameters
172 fAlphaGray = alpha1;
173 fAlphaBlack = alpha2;
174}
230d85c6 175