Bug corrected.
[u/mrichter/AliRoot.git] / STEER / AliITSPIDResponse.cxx
CommitLineData
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 29ClassImp(AliITSPIDResponse)
30
15e979c9 31AliITSPIDResponse::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{
99daa709 53 fBBtpcits[0]=1.04;
54 fBBtpcits[1]=27.14;
55 fBBtpcits[2]=1.00;
56 fBBtpcits[3]=0.964;
57 fBBtpcits[4]=2.59;
646e694f 58 fBBsa[0]=-2.48;
59 fBBsa[1]=23.13;
60 fBBsa[2]=1.161;
61 fBBsa[3]=0.93;
62 fBBsa[4]=-1.2973;
15e979c9 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//_________________________________________________________________________
69AliITSPIDResponse::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 83Double_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 94Double_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
122Double_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 137void 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