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2 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
4 * Author: The ALICE Off-line Project. *
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19 // Experimental data inspired Gray Particle Model for p-Pb collisions
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.
26 #include "AliSlowNucleonModelExp.h"
27 #include "AliCollisionGeometry.h"
30 ClassImp(AliSlowNucleonModelExp)
33 AliSlowNucleonModelExp::AliSlowNucleonModelExp():
38 fApplySaturation(kTRUE),
43 // Default constructor
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);
52 void AliSlowNucleonModelExp::GetNumberOfSlowNucleons(AliCollisionGeometry* geo,
53 Int_t& ngp, Int_t& ngn, Int_t & nbp, Int_t & nbn) const
56 // Return the number of black and gray nucleons
58 // Number of collisions
60 Int_t nu = geo->NN() + geo->NwN() + geo->NNw();
62 // Mean number of gray nucleons
64 Float_t nGray = fAlphaGray * nu;
65 Float_t nGrayNeutrons = nGray * fN / (fN + fP);
66 Float_t nGrayProtons = nGray - nGrayNeutrons;
68 // Mean number of black nucleons
70 if(!fApplySaturation || (fApplySaturation && nGray<fnGraySaturation)) nBlack = fAlphaBlack * nu;
71 else if(fApplySaturation && nGray>=fnGraySaturation) nBlack = fnBlackSaturation;
72 Float_t nBlackNeutrons = nBlack * 0.84;
73 Float_t nBlackProtons = nBlack - nBlackNeutrons;
75 // Actual number (including fluctuations) from binomial distribution
80 ngn = gRandom->Binomial((Int_t) fN, p);
84 ngp = gRandom->Binomial((Int_t) fP, p);
87 p = nBlackNeutrons/fN;
88 nbn = gRandom->Binomial((Int_t) fN, p);
92 nbp = gRandom->Binomial((Int_t) fP, p);
96 void AliSlowNucleonModelExp::SetParameters(Float_t alpha1, Float_t alpha2)
98 // Set the model parameters
100 fAlphaBlack = alpha2;