1 /**************************************************************************
2 * Copyright(c) 2005-2007, 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 **************************************************************************/
18 //-----------------------------------------------------------------
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 //-----------------------------------------------------------------
25 #include "AliVTrack.h"
26 #include "AliITSPIDResponse.h"
27 #include "AliITSPidParams.h"
28 #include "AliExternalTrackParam.h"
30 ClassImp(AliITSPIDResponse)
32 AliITSPIDResponse::AliITSPIDResponse(Bool_t isMC):
46 fBBdeu[0]=76.43; // parameters for the deuteron - tpcits - value from PbPb 2010 run (S.Trogolo - July 2014)
51 fBBtri[0]=13.34; // parameters for the triton - tpcits - value from PbPb 2010 run (S.Trogolo - July 2014)
56 fBBsa[0]=2.73198E7; //pure PHOBOS parameterization
61 fBBsaHybrid[0]=1.43505E7; //PHOBOS+Polinomial parameterization
62 fBBsaHybrid[1]=49.3402;
63 fBBsaHybrid[2]=1.77741E-7;
64 fBBsaHybrid[3]=1.77741E-7;
65 fBBsaHybrid[4]=1.01311E-7;
66 fBBsaHybrid[5]=77.2777;
67 fBBsaHybrid[6]=33.4099;
68 fBBsaHybrid[7]=46.0089;
69 fBBsaHybrid[8]=-2.26583;
70 fBBsaElectron[0]=4.05799E6; //electrons in the ITS
71 fBBsaElectron[1]=38.5713;
72 fBBsaElectron[2]=1.46462E-7;
73 fBBsaElectron[3]=1.46462E-7;
74 fBBsaElectron[4]=4.40284E-7;
75 fResolSA[0]=1.; // 0 cluster tracks should not be used
76 fResolSA[1]=0.25; // rough values for tracks with 1
77 fResolSA[2]=0.131; // value from pp 2010 run (L. Milano, 16-Jun-11)
78 fResolSA[3]=0.113; // value from pp 2010 run
79 fResolSA[4]=0.104; // value from pp 2010 run
80 for(Int_t i=0; i<5;i++) fResolTPCITS[i]=0.13;
81 fResolTPCITSDeu3[0]=0.06918; // deuteron resolution vs p
82 fResolTPCITSDeu3[1]=0.02498; // 3 ITS clusters for PId
83 fResolTPCITSDeu3[2]=1.1; // value from PbPb 2010 run (July 2014)
84 fResolTPCITSDeu4[0]=0.06756;// deuteron resolution vs p
85 fResolTPCITSDeu4[1]=0.02078; // 4 ITS clusters for PId
86 fResolTPCITSDeu4[2]=1.05; // value from PbPb 2010 run (July 2014)
87 fResolTPCITSTri3[0]=0.07239; // triton resolution vs p
88 fResolTPCITSTri3[1]=0.0192; // 3 ITS clusters for PId
89 fResolTPCITSTri3[2]=1.1; // value from PbPb 2010 run (July 2014)
90 fResolTPCITSTri4[0]=0.06083; // triton resolution
91 fResolTPCITSTri4[1]=0.02579; // 4 ITS clusters for PId
92 fResolTPCITSTri4[2]=1.15; // value from PbPb 2010 run (July 2014)
99 fBBsa[0]=2.02078E7; //pure PHOBOS parameterization
104 fBBsaHybrid[0]=1.05381E7; //PHOBOS+Polinomial parameterization
105 fBBsaHybrid[1]=89.3933;
106 fBBsaHybrid[2]=2.4831E-7;
107 fBBsaHybrid[3]=2.4831E-7;
108 fBBsaHybrid[4]=7.80591E-8;
109 fBBsaHybrid[5]=62.9214;
110 fBBsaHybrid[6]=32.347;
111 fBBsaHybrid[7]=58.7661;
112 fBBsaHybrid[8]=-3.39869;
113 fBBsaElectron[0]=2.26807E6; //electrons in the ITS
114 fBBsaElectron[1]=99.985;
115 fBBsaElectron[2]=0.000714841;
116 fBBsaElectron[3]=0.000259585;
117 fBBsaElectron[4]=1.39412E-7;
118 fResolSA[0]=1.; // 0 cluster tracks should not be used
119 fResolSA[1]=0.25; // rough values for tracks with 1
120 fResolSA[2]=0.126; // value from pp 2010 simulations (L. Milano, 16-Jun-11)
121 fResolSA[3]=0.109; // value from pp 2010 simulations
122 fResolSA[4]=0.097; // value from pp 2010 simulations
123 for(Int_t i=0; i<5;i++) fResolTPCITS[i]=0.13;
128 //_________________________________________________________________________
129 AliITSPIDResponse::AliITSPIDResponse(Double_t *param):
138 // The main constructor
140 for (Int_t i=0; i<5;i++) {
149 //_________________________________________________________________________
150 Double_t AliITSPIDResponse::BetheAleph(Double_t p, Double_t mass) const {
152 // returns AliExternalTrackParam::BetheBloch normalized to
153 // fgMIP at the minimum
157 AliExternalTrackParam::BetheBlochAleph(p/mass,fKp1,fKp2,fKp3,fKp4,fKp5);
161 //_________________________________________________________________________
162 Double_t AliITSPIDResponse::Bethe(Double_t bg, const Double_t * const par, Bool_t isNuclei) const
165 const Double_t beta = bg/TMath::Sqrt(1.+ bg*bg);
166 const Double_t gamma=bg/beta;
171 eff=(bg-par[3])*(bg-par[3])+par[4];
173 eff=(par[2]-par[3])*(par[2]-par[3])+par[4];
175 if(gamma>=0. && beta>0.){
177 //Parameterization for deuteron between 0.4 - 1.5 GeV/c; triton between 0.58 - 1.65 GeV/c
178 bb=par[0] + par[1]/bg + par[2]/(bg*bg) + par[3]/(bg*bg*bg) + par[4]/(bg*bg*bg*bg);
179 }else{ //Parameterization for pion, kaon, proton, electron
180 bb=(par[1]+2.0*TMath::Log(gamma)-beta*beta)*(par[0]/(beta*beta))*eff;
187 //_________________________________________________________________________
188 Double_t AliITSPIDResponse::Bethe(Double_t p, Double_t mass, Bool_t isSA) const {
190 //OLD - Mantained for backward compatibility
191 //from the mass check --> Set the Particle Type
192 //at the end use the method Bethe(Double_t p, AliPID::EParticleType species, Bool_t isSA) const to set the right parameter
195 // returns AliExternalTrackParam::BetheBloch normalized to
196 // fgMIP at the minimum
199 // NEW: Parameterization for Deuteron and Triton energy loss, reproduced with a polynomial in fixed p range
200 // fBBdeu --> parameters for deuteron
201 // fBBtri --> parameters for triton
204 //NOTE: if changes are made here, please also check the alternative function below
207 AliPID::EParticleType species = AliPID::kPion;
209 if(TMath::AreEqualAbs(mass,AliPID::ParticleMass(0),0.00001)){
210 //if is an electron use a specific BB parameterization
211 //To be used only between 100 and 160 MeV/c
212 species=AliPID::kElectron;
215 if(TMath::AreEqualAbs(mass,AliPID::ParticleMass(5),0.002)) species=AliPID::kDeuteron;
216 if(TMath::AreEqualAbs(mass,AliPID::ParticleMass(6),0.001)) species=AliPID::kTriton;
218 return Bethe(p,species,isSA);
221 //_________________________________________________________________________
222 Double_t AliITSPIDResponse::Bethe(Double_t p, AliPID::EParticleType species, Bool_t isSA) const
225 // Alternative bethe function assuming a particle type not a mass
226 // should be slightly faster
229 const Double_t m=AliPID::ParticleMassZ(species);
230 const Double_t bg=p/m;
231 Bool_t isNuclei=kFALSE;
234 //NOTE: if changes are made here, please also check the alternative function above
236 const Double_t *par=fBBtpcits;
238 if(species == AliPID::kElectron){
239 //if is an electron use a specific BB parameterization
240 //To be used only between 100 and 160 MeV/c
246 if(species == AliPID::kDeuteron) {
250 if(species == AliPID::kTriton ) {
256 return Bethe(bg, par, isNuclei);
259 //_________________________________________________________________________
260 Double_t AliITSPIDResponse::BetheITSsaHybrid(Double_t p, Double_t mass) const {
262 // returns AliExternalTrackParam::BetheBloch normalized to
263 // fgMIP at the minimum. The PHOBOS parameterization is used for beta*gamma>0.76.
264 // For beta*gamma<0.76 a polinomial function is used
267 Double_t beta = bg/TMath::Sqrt(1.+ bg*bg);
268 Double_t gamma=bg/beta;
272 //parameters for pi, K, p
273 for(Int_t ip=0; ip<9;ip++) par[ip]=fBBsaHybrid[ip];
274 //if it is an electron the PHOBOS part of the parameterization is tuned for e
275 //in the range used for identification beta*gamma is >0.76 for electrons
276 //To be used only between 100 and 160 MeV/c
277 if(mass>0.0005 && mass<0.00052)for(Int_t ip=0; ip<5;ip++) par[ip]=fBBsaElectron[ip];
279 if(gamma>=0. && beta>0. && bg>0.1){
283 eff=(bg-par[3])*(bg-par[3])+par[4];
285 eff=(par[2]-par[3])*(par[2]-par[3])+par[4];
287 bb=(par[1]+2.0*TMath::Log(gamma)-beta*beta)*(par[0]/(beta*beta))*eff;
289 bb=par[5] + par[6]/bg + par[7]/(bg*bg) + par[8]/(bg*bg*bg);
295 //_________________________________________________________________________
296 Double_t AliITSPIDResponse::GetResolution(Double_t bethe,
300 AliPID::EParticleType type) const {
302 // Calculate expected resolution for truncated mean
304 // NEW: Added new variables which are Double_t p and AliPID::EParticleType type
305 // AliPID::EParticleType type is used to set the correct resolution for the different particles
306 // default -> AliPID::EParticleType type = AliPID::kPion
307 // Double_t p is used for the resolution of deuteron and triton, because they are function of the momentum
308 // default -> Double_t p=0.
311 Double_t c=1.; //this is a correction factor used for the nuclei resolution, while for pion/kaon/proton/electron is 1.
313 if(isSA) r=fResolSA[nPtsForPid];
315 const Double_t *par=0x0;
316 if(type==AliPID::kDeuteron){
317 if(nPtsForPid==3) par = fResolTPCITSDeu3;
318 if(nPtsForPid==4) par = fResolTPCITSDeu4;
321 } else if(type==AliPID::kTriton){
322 if(nPtsForPid==3) par = fResolTPCITSTri3;
323 if(nPtsForPid==4) par = fResolTPCITSTri4;
327 r=fResolTPCITS[nPtsForPid];
335 //_________________________________________________________________________
336 void AliITSPIDResponse::GetITSProbabilities(Float_t mom, Double_t qclu[4], Double_t condprobfun[AliPID::kSPECIES], Bool_t isMC) const {
338 // Method to calculate PID probabilities for a single track
339 // using the likelihood method
341 const Int_t nLay = 4;
342 const Int_t nPart= 4;
344 static AliITSPidParams pars(isMC); // Pid parametrisation parameters
346 Double_t itsProb[nPart] = {1,1,1,1}; // e, p, K, pi
348 for (Int_t iLay = 0; iLay < nLay; iLay++) {
349 if (qclu[iLay] <= 50.)
352 Float_t dedx = qclu[iLay];
353 Float_t layProb = pars.GetLandauGausNorm(dedx,AliPID::kProton,mom,iLay+3);
354 itsProb[0] *= layProb;
356 layProb = pars.GetLandauGausNorm(dedx,AliPID::kKaon,mom,iLay+3);
357 itsProb[1] *= layProb;
359 layProb = pars.GetLandauGausNorm(dedx,AliPID::kPion,mom,iLay+3);
360 itsProb[2] *= layProb;
362 layProb = pars.GetLandauGausNorm(dedx,AliPID::kElectron,mom,iLay+3);
363 itsProb[3] *= layProb;
366 // Normalise probabilities
367 Double_t sumProb = 0;
368 for (Int_t iPart = 0; iPart < nPart; iPart++) {
369 sumProb += itsProb[iPart];
371 sumProb += itsProb[2]; // muon cannot be distinguished from pions
373 for (Int_t iPart = 0; iPart < nPart; iPart++) {
374 itsProb[iPart]/=sumProb;
376 condprobfun[AliPID::kElectron] = itsProb[3];
377 condprobfun[AliPID::kMuon] = itsProb[2];
378 condprobfun[AliPID::kPion] = itsProb[2];
379 condprobfun[AliPID::kKaon] = itsProb[1];
380 condprobfun[AliPID::kProton] = itsProb[0];
384 //_________________________________________________________________________
385 Double_t AliITSPIDResponse::GetNumberOfSigmas( const AliVTrack* track, AliPID::EParticleType type) const
390 UChar_t clumap=track->GetITSClusterMap();
391 Int_t nPointsForPid=0;
392 for(Int_t i=2; i<6; i++){
393 if(clumap&(1<<i)) ++nPointsForPid;
395 Float_t mom=track->P();
397 //check for ITS standalone tracks
399 if( track->GetStatus() & AliVTrack::kTPCin ) isSA=kFALSE;
401 const Float_t dEdx=track->GetITSsignal();
403 //TODO: in case of the electron, use the SA parametrisation,
404 // this needs to be changed if ITS provides a parametrisation
405 // for electrons also for ITS+TPC tracks
406 return GetNumberOfSigmas(mom,dEdx,type,nPointsForPid,isSA || (type==AliPID::kElectron));
409 //_________________________________________________________________________
410 Double_t AliITSPIDResponse::GetSignalDelta( const AliVTrack* track, AliPID::EParticleType type, Bool_t ratio/*=kFALSE*/) const
415 const Float_t mom=track->P();
416 const Double_t chargeFactor = TMath::Power(AliPID::ParticleCharge(type),2.);
418 if( track->GetStatus() & AliVTrack::kTPCin ) isSA=kFALSE;
420 const Float_t dEdx=track->GetITSsignal();
422 //TODO: in case of the electron, use the SA parametrisation,
423 // this needs to be changed if ITS provides a parametrisation
424 // for electrons also for ITS+TPC tracks
426 const Float_t bethe = Bethe(mom,AliPID::ParticleMassZ(type), isSA || (type==AliPID::kElectron))*chargeFactor;
428 Double_t delta=-9999.;
429 if (!ratio) delta=dEdx-bethe;
430 else if (bethe>1.e-20) delta=dEdx/bethe;
435 //_________________________________________________________________________
436 Int_t AliITSPIDResponse::GetParticleIdFromdEdxVsP(Float_t mom, Float_t signal, Bool_t isSA) const{
437 // method to get particle identity with simple cuts on dE/dx vs. momentum
439 Double_t massp=AliPID::ParticleMass(AliPID::kProton);
440 Double_t massk=AliPID::ParticleMass(AliPID::kKaon);
441 Double_t bethep=Bethe(mom,massp,isSA);
442 Double_t bethek=Bethe(mom,massk,isSA);
443 if(signal>(0.5*(bethep+bethek))) return AliPID::kProton;
444 Double_t masspi=AliPID::ParticleMass(AliPID::kPion);
445 Double_t bethepi=Bethe(mom,masspi,isSA);
446 if(signal>(0.5*(bethepi+bethek))) return AliPID::kKaon;
447 return AliPID::kPion;