-> Trigger configuration for p-Pb: modifications to cascade code
[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. *
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4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
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8 * documentation strictly for non-commercial purposes is hereby granted *
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11 * appear in the supporting documentation. The authors make no claims *
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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),
36 fAlphaGray(2.),
230d85c6 37 fAlphaBlack(4.),
38 fApplySaturation(kTRUE),
39 fnGraySaturation(15),
40 fnBlackSaturation(28)
c9a8628a 41{
ac3faee4 42 //
43 // Default constructor
44 //
c9a8628a 45}
46
47
48void AliSlowNucleonModelExp::GetNumberOfSlowNucleons(AliCollisionGeometry* geo,
ac3faee4 49 Int_t& ngp, Int_t& ngn, Int_t & nbp, Int_t & nbn) const
c9a8628a 50{
51//
52// Return the number of black and gray nucleons
53//
54// Number of collisions
55
993be958 56 Int_t nu = geo->NN() + geo->NwN() + geo->NNw();
c9a8628a 57
58// Mean number of gray nucleons
59
60 Float_t nGray = fAlphaGray * nu;
61 Float_t nGrayNeutrons = nGray * fN / (fN + fP);
62 Float_t nGrayProtons = nGray - nGrayNeutrons;
63
64// Mean number of black nucleons
230d85c6 65 Float_t nBlack = 0.;
66 if(!fApplySaturation || (fApplySaturation && nGray<fnGraySaturation)) nBlack = fAlphaBlack * nu;
67 else if(fApplySaturation && nGray>=fnGraySaturation) nBlack = fnBlackSaturation;
c9a8628a 68 Float_t nBlackNeutrons = nBlack * fN / (fN + fP);
69 Float_t nBlackProtons = nBlack - nBlackNeutrons;
70
71// Actual number (including fluctuations) from binomial distribution
72 Double_t p;
73
74// gray neutrons
75 p = nGrayNeutrons/fN;
76 ngn = gRandom->Binomial((Int_t) fN, p);
77
78// gray protons
79 p = nGrayProtons/fP;
80 ngp = gRandom->Binomial((Int_t) fP, p);
81
82// black neutrons
83 p = nBlackNeutrons/fN;
84 nbn = gRandom->Binomial((Int_t) fN, p);
85
86// black protons
87 p = nBlackProtons/fP;
88 nbp = gRandom->Binomial((Int_t) fP, p);
89
90}
91
92void AliSlowNucleonModelExp::SetParameters(Float_t alpha1, Float_t alpha2)
93{
94 // Set the model parameters
95 fAlphaGray = alpha1;
96 fAlphaBlack = alpha2;
97}
230d85c6 98