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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 | ||
16 | /* $Id$ */ | |
17 | ||
18 | // | |
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. | |
23 | // Author: A.Morsch | |
24 | // | |
25 | ||
26 | #include "AliSlowNucleonModelExp.h" | |
27 | #include "AliCollisionGeometry.h" | |
28 | #include <TRandom.h> | |
29 | ||
30 | ClassImp(AliSlowNucleonModelExp) | |
31 | ||
32 | AliSlowNucleonModelExp::AliSlowNucleonModelExp() | |
33 | { | |
34 | // | |
35 | // Default constructor | |
36 | // | |
37 | fP = 82; | |
38 | fN = 208 - 82; | |
39 | fAlphaGray = 2.; | |
40 | fAlphaBlack = 4.; | |
41 | } | |
42 | ||
43 | ||
44 | void AliSlowNucleonModelExp::GetNumberOfSlowNucleons(AliCollisionGeometry* geo, | |
45 | Int_t& ngp, Int_t& ngn, Int_t & nbp, Int_t & nbn) const | |
46 | { | |
47 | // | |
48 | // Return the number of black and gray nucleons | |
49 | // | |
50 | // Number of collisions | |
51 | ||
52 | Int_t nu = geo->NwN() + geo->NNw(); | |
53 | ||
54 | // Mean number of gray nucleons | |
55 | ||
56 | Float_t nGray = fAlphaGray * nu; | |
57 | Float_t nGrayNeutrons = nGray * fN / (fN + fP); | |
58 | Float_t nGrayProtons = nGray - nGrayNeutrons; | |
59 | ||
60 | // Mean number of black nucleons | |
61 | Float_t nBlack = fAlphaBlack * nu; | |
62 | Float_t nBlackNeutrons = nBlack * fN / (fN + fP); | |
63 | Float_t nBlackProtons = nBlack - nBlackNeutrons; | |
64 | ||
65 | // Actual number (including fluctuations) from binomial distribution | |
66 | Double_t p; | |
67 | ||
68 | // gray neutrons | |
69 | p = nGrayNeutrons/fN; | |
70 | ngn = gRandom->Binomial((Int_t) fN, p); | |
71 | ||
72 | // gray protons | |
73 | p = nGrayProtons/fP; | |
74 | ngp = gRandom->Binomial((Int_t) fP, p); | |
75 | ||
76 | // black neutrons | |
77 | p = nBlackNeutrons/fN; | |
78 | nbn = gRandom->Binomial((Int_t) fN, p); | |
79 | ||
80 | // black protons | |
81 | p = nBlackProtons/fP; | |
82 | nbp = gRandom->Binomial((Int_t) fP, p); | |
83 | ||
84 | } | |
85 | ||
86 | void AliSlowNucleonModelExp::SetParameters(Float_t alpha1, Float_t alpha2) | |
87 | { | |
88 | // Set the model parameters | |
89 | fAlphaGray = alpha1; | |
90 | fAlphaBlack = alpha2; | |
91 | } |