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10d100d4 | 1 | /************************************************************************** |
2 | * Copyright(c) 2005-2007, 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 | // ITS PID method # 1 | |
20 | // Implementation of the ITS PID class | |
21 | // Very naive one... Should be made better by the detector experts... | |
22 | // Origin: Iouri Belikov, CERN, Jouri.Belikov@cern.ch | |
23 | //----------------------------------------------------------------- | |
24 | #include "TMath.h" | |
25 | #include "AliITSPIDResponse.h" | |
26 | #include "AliITSPidParams.h" | |
27 | #include "AliExternalTrackParam.h" | |
28 | ||
10d100d4 | 29 | ClassImp(AliITSPIDResponse) |
30 | ||
31 | AliITSPIDResponse::AliITSPIDResponse(): | |
32 | fRes(0.13), | |
33 | fKp1(15.77), | |
34 | fKp2(4.95), | |
35 | fKp3(0.312), | |
36 | fKp4(2.14), | |
37 | fKp5(0.82) | |
38 | { | |
39 | } | |
40 | ||
41 | //_________________________________________________________________________ | |
42 | AliITSPIDResponse::AliITSPIDResponse(Double_t *param): | |
9ebbddd4 | 43 | fRes(param[0]), |
10d100d4 | 44 | fKp1(15.77), |
45 | fKp2(4.95), | |
46 | fKp3(0.312), | |
47 | fKp4(2.14), | |
48 | fKp5(0.82) | |
49 | { | |
50 | // | |
51 | // The main constructor | |
52 | // | |
10d100d4 | 53 | } |
54 | ||
55 | ||
56 | Double_t AliITSPIDResponse::Bethe(Double_t p,Double_t mass) const { | |
57 | // | |
58 | // returns AliExternalTrackParam::BetheBloch normalized to | |
59 | // fgMIP at the minimum | |
60 | // | |
61 | Double_t bb= | |
62 | AliExternalTrackParam::BetheBlochAleph(p/mass,fKp1,fKp2,fKp3,fKp4,fKp5); | |
9ebbddd4 | 63 | return bb; |
10d100d4 | 64 | } |
65 | ||
66 | Double_t AliITSPIDResponse::GetResolution(Double_t bethe) const { | |
67 | // | |
68 | // Calculate expected resolution for truncated mean | |
69 | // | |
70 | return fRes*bethe; | |
71 | } | |
72 | ||
73 | void AliITSPIDResponse::GetITSProbabilities(Float_t mom, Double_t qclu[4], Double_t condprobfun[AliPID::kSPECIES]) const { | |
74 | // | |
75 | // Method to calculate PID probabilities for a single track | |
76 | // using the likelihood method | |
77 | // | |
78 | const Int_t nLay = 4; | |
79 | const Int_t nPart = 3; | |
80 | ||
81 | static AliITSPidParams pars; // Pid parametrisation parameters | |
82 | ||
83 | Double_t itsProb[nPart] = {1,1,1}; // p, K, pi | |
84 | ||
85 | for (Int_t iLay = 0; iLay < nLay; iLay++) { | |
86 | if (qclu[iLay] <= 0) | |
87 | continue; | |
88 | ||
89 | Float_t dedx = qclu[iLay]; | |
90 | Float_t layProb = pars.GetLandauGausNorm(dedx,AliPID::kProton,mom,iLay+3); | |
91 | itsProb[0] *= layProb; | |
92 | ||
93 | layProb = pars.GetLandauGausNorm(dedx,AliPID::kKaon,mom,iLay+3); | |
94 | if (mom < 0.16) layProb=0.00001; | |
95 | itsProb[1] *= layProb; | |
96 | ||
97 | layProb = pars.GetLandauGausNorm(dedx,AliPID::kPion,mom,iLay+3); | |
98 | itsProb[2] *= layProb; | |
99 | } | |
100 | ||
101 | // Normalise probabilities | |
102 | Double_t sumProb = 0; | |
103 | for (Int_t iPart = 0; iPart < nPart; iPart++) { | |
104 | sumProb += itsProb[iPart]; | |
105 | } | |
106 | ||
107 | for (Int_t iPart = 0; iPart < nPart; iPart++) { | |
108 | itsProb[iPart]/=sumProb; | |
109 | } | |
110 | ||
111 | condprobfun[AliPID::kElectron] = itsProb[2]/3.; | |
112 | condprobfun[AliPID::kMuon] = itsProb[2]/3.; | |
113 | condprobfun[AliPID::kPion] = itsProb[2]/3.; | |
114 | condprobfun[AliPID::kKaon] = itsProb[1]; | |
115 | condprobfun[AliPID::kProton] = itsProb[0]; | |
116 | return; | |
117 | } |