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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 | ||
15e979c9 | 31 | AliITSPIDResponse::AliITSPIDResponse(Bool_t isMC): |
10d100d4 | 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 | { | |
15e979c9 | 39 | if(!isMC){ |
40 | fBBtpcits[0]=0.73; | |
41 | fBBtpcits[1]=14.68; | |
42 | fBBtpcits[2]=0.905; | |
43 | fBBtpcits[3]=1.2; | |
44 | fBBtpcits[4]=6.6; | |
45 | fBBsa[0]=5.33458E4; | |
46 | fBBsa[1]=16.5303; | |
47 | fBBsa[2]=2.60065E-3; | |
48 | fBBsa[3]=3.59533E-4; | |
49 | fBBsa[4]=7.51168E-5; | |
50 | for(Int_t i=0; i<5;i++) fResolSA[i]=0.15; | |
51 | for(Int_t i=0; i<5;i++) fResolTPCITS[i]=0.13; | |
52 | }else{ | |
53 | fBBtpcits[0]=0.73; | |
54 | fBBtpcits[1]=14.68; | |
55 | fBBtpcits[2]=0.905; | |
56 | fBBtpcits[3]=0.2; | |
57 | fBBtpcits[4]=6.6; | |
58 | fBBsa[0]=139.1; | |
59 | fBBsa[1]=23.36; | |
60 | fBBsa[2]=0.06052; | |
61 | fBBsa[3]=0.2043; | |
62 | fBBsa[4]=-0.0004999; | |
63 | for(Int_t i=0; i<5;i++) fResolSA[i]=0.15; | |
64 | for(Int_t i=0; i<5;i++) fResolTPCITS[i]=0.13; | |
65 | } | |
10d100d4 | 66 | } |
67 | ||
68 | //_________________________________________________________________________ | |
69 | AliITSPIDResponse::AliITSPIDResponse(Double_t *param): | |
9ebbddd4 | 70 | fRes(param[0]), |
10d100d4 | 71 | fKp1(15.77), |
72 | fKp2(4.95), | |
73 | fKp3(0.312), | |
74 | fKp4(2.14), | |
75 | fKp5(0.82) | |
76 | { | |
77 | // | |
78 | // The main constructor | |
79 | // | |
10d100d4 | 80 | } |
81 | ||
82 | ||
15e979c9 | 83 | Double_t AliITSPIDResponse::BetheAleph(Double_t p, Double_t mass) const { |
10d100d4 | 84 | // |
85 | // returns AliExternalTrackParam::BetheBloch normalized to | |
86 | // fgMIP at the minimum | |
87 | // | |
15e979c9 | 88 | |
10d100d4 | 89 | Double_t bb= |
90 | AliExternalTrackParam::BetheBlochAleph(p/mass,fKp1,fKp2,fKp3,fKp4,fKp5); | |
9ebbddd4 | 91 | return bb; |
10d100d4 | 92 | } |
93 | ||
15e979c9 | 94 | Double_t AliITSPIDResponse::Bethe(Double_t p, Double_t mass, Bool_t isSA) const { |
95 | // | |
96 | // returns AliExternalTrackParam::BetheBloch normalized to | |
97 | // fgMIP at the minimum | |
98 | // | |
99 | ||
100 | Double_t bg=p/mass; | |
101 | Double_t beta = bg/TMath::Sqrt(1.+ bg*bg); | |
102 | Double_t gamma=bg/beta; | |
103 | Double_t par[5]; | |
104 | if(isSA){ | |
105 | for(Int_t ip=0; ip<5;ip++) par[ip]=fBBsa[ip]; | |
106 | }else{ | |
107 | for(Int_t ip=0; ip<5;ip++) par[ip]=fBBtpcits[ip]; | |
108 | } | |
109 | Double_t eff=1.0; | |
110 | if(bg<par[2]) | |
111 | eff=(bg-par[3])*(bg-par[3])+par[4]; | |
112 | else | |
113 | eff=(par[2]-par[3])*(par[2]-par[3])+par[4]; | |
114 | ||
115 | Double_t bb=0.; | |
116 | if(gamma>=0. && beta>0.){ | |
117 | bb=(par[1]+2.0*TMath::Log(gamma)-beta*beta)*(par[0]/(beta*beta))*eff; | |
118 | } | |
119 | return bb; | |
120 | } | |
121 | ||
122 | Double_t AliITSPIDResponse::GetResolution(Double_t bethe, | |
123 | Int_t nPtsForPid, | |
124 | Bool_t isSA) const { | |
10d100d4 | 125 | // |
126 | // Calculate expected resolution for truncated mean | |
127 | // | |
15e979c9 | 128 | Float_t r; |
129 | if(isSA) r=fResolSA[nPtsForPid]; | |
130 | else r=fResolTPCITS[nPtsForPid]; | |
131 | return r*bethe; | |
10d100d4 | 132 | } |
133 | ||
15e979c9 | 134 | |
135 | ||
136 | ||
10d100d4 | 137 | void AliITSPIDResponse::GetITSProbabilities(Float_t mom, Double_t qclu[4], Double_t condprobfun[AliPID::kSPECIES]) const { |
138 | // | |
139 | // Method to calculate PID probabilities for a single track | |
140 | // using the likelihood method | |
141 | // | |
142 | const Int_t nLay = 4; | |
143 | const Int_t nPart = 3; | |
144 | ||
145 | static AliITSPidParams pars; // Pid parametrisation parameters | |
146 | ||
147 | Double_t itsProb[nPart] = {1,1,1}; // p, K, pi | |
148 | ||
149 | for (Int_t iLay = 0; iLay < nLay; iLay++) { | |
150 | if (qclu[iLay] <= 0) | |
151 | continue; | |
152 | ||
153 | Float_t dedx = qclu[iLay]; | |
154 | Float_t layProb = pars.GetLandauGausNorm(dedx,AliPID::kProton,mom,iLay+3); | |
155 | itsProb[0] *= layProb; | |
156 | ||
157 | layProb = pars.GetLandauGausNorm(dedx,AliPID::kKaon,mom,iLay+3); | |
158 | if (mom < 0.16) layProb=0.00001; | |
159 | itsProb[1] *= layProb; | |
160 | ||
161 | layProb = pars.GetLandauGausNorm(dedx,AliPID::kPion,mom,iLay+3); | |
162 | itsProb[2] *= layProb; | |
163 | } | |
164 | ||
165 | // Normalise probabilities | |
166 | Double_t sumProb = 0; | |
167 | for (Int_t iPart = 0; iPart < nPart; iPart++) { | |
168 | sumProb += itsProb[iPart]; | |
169 | } | |
170 | ||
171 | for (Int_t iPart = 0; iPart < nPart; iPart++) { | |
172 | itsProb[iPart]/=sumProb; | |
173 | } | |
174 | ||
175 | condprobfun[AliPID::kElectron] = itsProb[2]/3.; | |
176 | condprobfun[AliPID::kMuon] = itsProb[2]/3.; | |
177 | condprobfun[AliPID::kPion] = itsProb[2]/3.; | |
178 | condprobfun[AliPID::kKaon] = itsProb[1]; | |
179 | condprobfun[AliPID::kProton] = itsProb[0]; | |
180 | return; | |
181 | } | |
15e979c9 | 182 |