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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 | |
18 | // Experimental data inspired Gray Particle Model for p-Pb collisions | |
19 | // | |
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. | |
23 | // | |
24 | ||
25 | #include "AliSlowNucleonModelExp.h" | |
26 | #include "AliCollisionGeometry.h" | |
27 | #include <TRandom.h> | |
28 | ||
29 | ClassImp(AliSlowNucleonModelExp) | |
30 | ||
31 | AliSlowNucleonModelExp::AliSlowNucleonModelExp() | |
32 | { | |
33 | // Default constructor | |
34 | fP = 82; | |
35 | fN = 208 - 82; | |
36 | fAlphaGray = 2.; | |
37 | fAlphaBlack = 4.; | |
38 | } | |
39 | ||
40 | ||
41 | void AliSlowNucleonModelExp::GetNumberOfSlowNucleons(AliCollisionGeometry* geo, | |
42 | Int_t& ngp, Int_t& ngn, Int_t & nbp, Int_t & nbn) | |
43 | { | |
44 | // | |
45 | // Return the number of black and gray nucleons | |
46 | // | |
47 | // Number of collisions | |
48 | ||
49 | Int_t nu = geo->NwN() + geo->NNw(); | |
50 | ||
51 | // Mean number of gray nucleons | |
52 | ||
53 | Float_t nGray = fAlphaGray * nu; | |
54 | Float_t nGrayNeutrons = nGray * fN / (fN + fP); | |
55 | Float_t nGrayProtons = nGray - nGrayNeutrons; | |
56 | ||
57 | // Mean number of black nucleons | |
58 | Float_t nBlack = fAlphaBlack * nu; | |
59 | Float_t nBlackNeutrons = nBlack * fN / (fN + fP); | |
60 | Float_t nBlackProtons = nBlack - nBlackNeutrons; | |
61 | ||
62 | // Actual number (including fluctuations) from binomial distribution | |
63 | Double_t p; | |
64 | ||
65 | // gray neutrons | |
66 | p = nGrayNeutrons/fN; | |
67 | ngn = gRandom->Binomial((Int_t) fN, p); | |
68 | ||
69 | // gray protons | |
70 | p = nGrayProtons/fP; | |
71 | ngp = gRandom->Binomial((Int_t) fP, p); | |
72 | ||
73 | // black neutrons | |
74 | p = nBlackNeutrons/fN; | |
75 | nbn = gRandom->Binomial((Int_t) fN, p); | |
76 | ||
77 | // black protons | |
78 | p = nBlackProtons/fP; | |
79 | nbp = gRandom->Binomial((Int_t) fP, p); | |
80 | ||
81 | } | |
82 | ||
83 | void AliSlowNucleonModelExp::SetParameters(Float_t alpha1, Float_t alpha2) | |
84 | { | |
85 | // Set the model parameters | |
86 | fAlphaGray = alpha1; | |
87 | fAlphaBlack = alpha2; | |
88 | } |