Possibility to use multiplcity as weight in the correction framework task, needed...
[u/mrichter/AliRoot.git] / EVGEN / AliSlowNucleonModelExp.cxx
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c9a8628a 1/**************************************************************************
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4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
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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.),
37 fAlphaBlack(4.)
c9a8628a 38{
ac3faee4 39 //
40 // Default constructor
41 //
c9a8628a 42}
43
44
45void AliSlowNucleonModelExp::GetNumberOfSlowNucleons(AliCollisionGeometry* geo,
ac3faee4 46 Int_t& ngp, Int_t& ngn, Int_t & nbp, Int_t & nbn) const
c9a8628a 47{
48//
49// Return the number of black and gray nucleons
50//
51// Number of collisions
52
53 Int_t nu = geo->NwN() + geo->NNw();
54
55// Mean number of gray nucleons
56
57 Float_t nGray = fAlphaGray * nu;
58 Float_t nGrayNeutrons = nGray * fN / (fN + fP);
59 Float_t nGrayProtons = nGray - nGrayNeutrons;
60
61// Mean number of black nucleons
62 Float_t nBlack = fAlphaBlack * nu;
63 Float_t nBlackNeutrons = nBlack * fN / (fN + fP);
64 Float_t nBlackProtons = nBlack - nBlackNeutrons;
65
66// Actual number (including fluctuations) from binomial distribution
67 Double_t p;
68
69// gray neutrons
70 p = nGrayNeutrons/fN;
71 ngn = gRandom->Binomial((Int_t) fN, p);
72
73// gray protons
74 p = nGrayProtons/fP;
75 ngp = gRandom->Binomial((Int_t) fP, p);
76
77// black neutrons
78 p = nBlackNeutrons/fN;
79 nbn = gRandom->Binomial((Int_t) fN, p);
80
81// black protons
82 p = nBlackProtons/fP;
83 nbp = gRandom->Binomial((Int_t) fP, p);
84
85}
86
87void AliSlowNucleonModelExp::SetParameters(Float_t alpha1, Float_t alpha2)
88{
89 // Set the model parameters
90 fAlphaGray = alpha1;
91 fAlphaBlack = alpha2;
92}