1 /**************************************************************************
2 * Copyright(c) 2009-2012, ALICE Experiment at CERN, All rights reserved. *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
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 **************************************************************************/
19 ///////////////////////////////////////////////////////////////////
21 // Class to store information for PID with ITS //
22 // and truncated mean computation methods //
23 // Origin: F.Prino, Torino, prino@to.infn.it //
25 ///////////////////////////////////////////////////////////////////
27 #include "AliITSPidParams.h"
28 #include "AliITSdEdxSamples.h"
32 ClassImp(AliITSdEdxSamples)
34 //______________________________________________________________________
35 AliITSdEdxSamples::AliITSdEdxSamples():TObject(),
40 // Default constructor
41 for(Int_t i=0; i<kMaxSamples; i++){
48 //______________________________________________________________________
49 AliITSdEdxSamples::AliITSdEdxSamples(Int_t nSamples, Double_t* esamples, Double_t* xsamples, Double_t mom, Int_t specie) :
53 fParticleSpecie(specie)
55 // Standard constructor
56 SetdESamples(nSamples,esamples);
57 SetdxSamples(nSamples,xsamples);
60 //______________________________________________________________________
61 AliITSdEdxSamples::AliITSdEdxSamples(const AliITSdEdxSamples& source) :
63 fNSamples(source.fNSamples),
65 fParticleSpecie(source.fParticleSpecie)
68 for(Int_t i=0; i<kMaxSamples; i++){
69 fdESamples[i]=source.GetdESample(i);
70 fdxSamples[i]=source.GetdxSample(i);
71 fPAtSample[i]=source.GetMomentumAtSample(i);
74 //______________________________________________________________________
75 void AliITSdEdxSamples::SetdESamples(Int_t nSamples, Double_t* samples){
78 if(nSamples>kMaxSamples){
79 AliWarning(Form("Too many dE samples,only first %d will be used",kMaxSamples));
80 fNSamples=kMaxSamples;
84 for(Int_t i=0; i<fNSamples; i++) fdESamples[i]=samples[i];
85 for(Int_t i=fNSamples; i<kMaxSamples; i++) fdESamples[i]=0.;
88 //______________________________________________________________________
89 void AliITSdEdxSamples::SetdxSamples(Int_t nSamples, Double_t* samples){
92 if(nSamples>kMaxSamples){
93 AliWarning(Form("Too many dx samples,only first %d will be used",kMaxSamples))
94 fNSamples=kMaxSamples;
98 for(Int_t i=0; i<fNSamples; i++) fdxSamples[i]=samples[i];
99 for(Int_t i=fNSamples; i<kMaxSamples; i++) fdxSamples[i]=0.;
103 //______________________________________________________________________
104 void AliITSdEdxSamples::SetSamplesAndMomenta(Int_t nSamples, Double_t* esamples, Double_t* xsamples, Double_t* mom){
106 SetdESamples(nSamples,esamples);
107 SetdxSamples(nSamples,xsamples);
108 for(Int_t i=0; i<fNSamples; i++) fPAtSample[i]=mom[i];
109 for(Int_t i=fNSamples; i<kMaxSamples; i++) fPAtSample[i]=0.;
112 //______________________________________________________________________
113 Double_t AliITSdEdxSamples::GetTruncatedMean(Double_t frac, Double_t mindedx) const {
114 // compute truncated mean
117 Double_t dedx[kMaxSamples];
118 for (Int_t il=0; il<fNSamples; il++) { // count good (>0) dE/dx values
119 Double_t dedxsamp=GetdEdxSample(il);
120 if(dedxsamp>mindedx){
127 Int_t swap; // sort in ascending order
130 for (Int_t i=0; i<nc-1; i++) {
131 if (dedx[i]<=dedx[i+1]) continue;
132 Double_t tmp=dedx[i];
139 Double_t sumamp=0,sumweight=0;
140 Double_t weight[kMaxSamples];
141 for(Int_t iw=0; iw<kMaxSamples; iw++) weight[iw]=0.;
142 Int_t lastUsed=(Int_t)(frac*nc+0.00001);
143 if(lastUsed==0) lastUsed=1;
144 if(lastUsed>kMaxSamples) lastUsed=kMaxSamples;
145 for(Int_t iw=0; iw<lastUsed; iw++) weight[iw]=1.;
146 if((frac*nc-lastUsed)>0.4 && lastUsed<kMaxSamples) weight[lastUsed]=0.5;
147 for (Int_t i=0; i<nc; i++) {
148 // AliDebug(5,Form("dE/dx %f weight %f",dedx[i],weight[i]));
149 sumamp+= dedx[i]*weight[i];
150 sumweight+=weight[i];
152 if(sumweight>0.) return sumamp/sumweight;
156 //______________________________________________________________________
157 Double_t AliITSdEdxSamples::GetWeightedMean(Double_t mindedx) const {
158 // compute generalized mean with k=-2 (used by CMS)
160 Double_t dedx[kMaxSamples];
161 for (Int_t il=0; il<fNSamples; il++) { // count good (>0) dE/dx values
162 Double_t dedxsamp=GetdEdxSample(il);
163 if(dedxsamp>mindedx){
170 Double_t weiSum = 0.;
171 for (Int_t i=0; i<nc; i++) {
172 weiSum+=TMath::Power(dedx[i],-2);
175 if(weiSum>0.) wMean= TMath::Power(weiSum/nc,-0.5);
179 //______________________________________________________________________
180 void AliITSdEdxSamples::GetConditionalProbabilities(AliITSPidParams* pars, Double_t condprob[AliPID::kSPECIES], Double_t mindedx) const {
181 // compute conditional probablilities
182 const Int_t nPart = 3;
183 Double_t itsProb[nPart] = {1,1,1}; // p, K, pi
185 for(Int_t iS=0; iS<fNSamples; iS++){
186 Int_t iLayer=iS+3; // to match with present ITS
187 if(iLayer>6) iLayer=6; // all extra points are treated as SSD
188 Float_t dedx = GetdEdxSample(iS);
189 if(dedx<mindedx) continue;
190 Float_t layProb = pars->GetLandauGausNorm(dedx,AliPID::kProton,fP,iLayer);
191 itsProb[0] *= layProb;
193 layProb = pars->GetLandauGausNorm(dedx,AliPID::kKaon,fP,iLayer);
194 if (fP < 0.16) layProb=0.00001;
195 itsProb[1] *= layProb;
197 layProb = pars->GetLandauGausNorm(dedx,AliPID::kPion,fP,iLayer);
198 itsProb[2] *= layProb;
201 // Normalise probabilities
202 Double_t sumProb = 0;
203 for (Int_t iPart = 0; iPart < nPart; iPart++) {
204 sumProb += itsProb[iPart];
206 sumProb += 2*itsProb[2]; // muon and electron cannot be distinguished from pions
208 for (Int_t iPart = 0; iPart < nPart; iPart++) {
209 itsProb[iPart]/=sumProb;
212 condprob[AliPID::kElectron] = itsProb[2];
213 condprob[AliPID::kMuon] = itsProb[2];
214 condprob[AliPID::kPion] = itsProb[2];
215 condprob[AliPID::kKaon] = itsProb[1];
216 condprob[AliPID::kProton] = itsProb[0];