Update to subtract fixed values of v2,3 (Redmer)
[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>
29
706938e6 30ClassImp(AliSlowNucleonModelExp)
c9a8628a 31
1c56e311 32
33AliSlowNucleonModelExp::AliSlowNucleonModelExp():
34 fP(82),
35 fN (208 - 82),
1ffc7bfa 36 fAlphaGray(2.3),
37 fAlphaBlack(3.6),
230d85c6 38 fApplySaturation(kTRUE),
39 fnGraySaturation(15),
40 fnBlackSaturation(28)
c9a8628a 41{
ac3faee4 42 //
43 // Default constructor
44 //
1ffc7bfa 45 //
46 printf("\n\nInitializing slow nucleon model with parameters:\n");
47 printf(" \t alpha_{gray} %1.2f alpha_{black} %1.2f\n",fAlphaGray, fAlphaBlack);
48 printf(" \t SATURATION %d w. %d (gray) %d (black) \n\n",fApplySaturation,fnGraySaturation,fnBlackSaturation);
c9a8628a 49}
50
51
52void AliSlowNucleonModelExp::GetNumberOfSlowNucleons(AliCollisionGeometry* geo,
ac3faee4 53 Int_t& ngp, Int_t& ngn, Int_t & nbp, Int_t & nbn) const
c9a8628a 54{
55//
56// Return the number of black and gray nucleons
57//
58// Number of collisions
59
993be958 60 Int_t nu = geo->NN() + geo->NwN() + geo->NNw();
c9a8628a 61
62// Mean number of gray nucleons
63
64 Float_t nGray = fAlphaGray * nu;
65 Float_t nGrayNeutrons = nGray * fN / (fN + fP);
66 Float_t nGrayProtons = nGray - nGrayNeutrons;
67
68// Mean number of black nucleons
230d85c6 69 Float_t nBlack = 0.;
70 if(!fApplySaturation || (fApplySaturation && nGray<fnGraySaturation)) nBlack = fAlphaBlack * nu;
71 else if(fApplySaturation && nGray>=fnGraySaturation) nBlack = fnBlackSaturation;
1ffc7bfa 72 Float_t nBlackNeutrons = nBlack * 0.84;
c9a8628a 73 Float_t nBlackProtons = nBlack - nBlackNeutrons;
74
75// Actual number (including fluctuations) from binomial distribution
76 Double_t p;
77
78// gray neutrons
79 p = nGrayNeutrons/fN;
80 ngn = gRandom->Binomial((Int_t) fN, p);
81
82// gray protons
83 p = nGrayProtons/fP;
84 ngp = gRandom->Binomial((Int_t) fP, p);
85
86// black neutrons
87 p = nBlackNeutrons/fN;
88 nbn = gRandom->Binomial((Int_t) fN, p);
89
90// black protons
91 p = nBlackProtons/fP;
92 nbp = gRandom->Binomial((Int_t) fP, p);
93
94}
95
96void AliSlowNucleonModelExp::SetParameters(Float_t alpha1, Float_t alpha2)
97{
98 // Set the model parameters
99 fAlphaGray = alpha1;
100 fAlphaBlack = alpha2;
101}
230d85c6 102