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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, Bool_t isNuclei) const {
191 // returns AliExternalTrackParam::BetheBloch normalized to
192 // fgMIP at the minimum
195 // NEW: Parameterization for Deuteron and Triton energy loss, reproduced with a polynomial in fixed p range
196 // fBBdeu --> parameters for deuteron
197 // fBBtri --> parameters for triton
200 const Double_t bg=p/mass;
203 //NOTE: if changes are made here, please also check the alternative function below
205 const Double_t *par=fBBtpcits;
207 if(TMath::AreEqualAbs(mass,AliPID::ParticleMass(0),0.00001)){
208 //if is an electron use a specific BB parameterization
209 //To be used only between 100 and 160 MeV/c
216 if(TMath::AreEqualAbs(mass,AliPID::ParticleMass(5),0.002)) par=fBBdeu;
217 if(TMath::AreEqualAbs(mass,AliPID::ParticleMass(6),0.001)) par=fBBtri;
221 return Bethe(bg, par, isNuclei);
224 //_________________________________________________________________________
225 Double_t AliITSPIDResponse::Bethe(Double_t p, AliPID::EParticleType species, Bool_t isSA) const
228 // Aliternative bethe function assuming a particle type not a mass
229 // should be slightly faster
232 const Double_t m=AliPID::ParticleMassZ(species);
233 const Double_t bg=p/m;
234 Bool_t isNuclei=kFALSE;
237 //NOTE: if changes are made here, please also check the alternative function above
239 const Double_t *par=fBBtpcits;
241 if(species == AliPID::kElectron){
242 //if is an electron use a specific BB parameterization
243 //To be used only between 100 and 160 MeV/c
249 if(species == AliPID::kDeuteron) {
253 if(species == AliPID::kTriton ) {
259 return Bethe(bg, par, isNuclei);
262 //_________________________________________________________________________
263 Double_t AliITSPIDResponse::BetheITSsaHybrid(Double_t p, Double_t mass) const {
265 // returns AliExternalTrackParam::BetheBloch normalized to
266 // fgMIP at the minimum. The PHOBOS parameterization is used for beta*gamma>0.76.
267 // For beta*gamma<0.76 a polinomial function is used
270 Double_t beta = bg/TMath::Sqrt(1.+ bg*bg);
271 Double_t gamma=bg/beta;
275 //parameters for pi, K, p
276 for(Int_t ip=0; ip<9;ip++) par[ip]=fBBsaHybrid[ip];
277 //if it is an electron the PHOBOS part of the parameterization is tuned for e
278 //in the range used for identification beta*gamma is >0.76 for electrons
279 //To be used only between 100 and 160 MeV/c
280 if(mass>0.0005 && mass<0.00052)for(Int_t ip=0; ip<5;ip++) par[ip]=fBBsaElectron[ip];
282 if(gamma>=0. && beta>0. && bg>0.1){
286 eff=(bg-par[3])*(bg-par[3])+par[4];
288 eff=(par[2]-par[3])*(par[2]-par[3])+par[4];
290 bb=(par[1]+2.0*TMath::Log(gamma)-beta*beta)*(par[0]/(beta*beta))*eff;
292 bb=par[5] + par[6]/bg + par[7]/(bg*bg) + par[8]/(bg*bg*bg);
298 //_________________________________________________________________________
299 Double_t AliITSPIDResponse::GetResolution(Double_t bethe,
303 AliPID::EParticleType type) const {
305 // Calculate expected resolution for truncated mean
307 // NEW: Added new variables which are Double_t p and AliPID::EParticleType type
308 // AliPID::EParticleType type is used to set the correct resolution for the different particles
309 // default -> AliPID::EParticleType type = AliPID::kPion
310 // Double_t p is used for the resolution of deuteron and triton, because they are function of the momentum
311 // default -> Double_t p=0.
314 Double_t c=1.; //this is a correction factor used for the nuclei resolution, while for pion/kaon/proton/electron is 1.
316 if(isSA) r=fResolSA[nPtsForPid];
318 const Double_t *par=0x0;
319 if(type==AliPID::kDeuteron){
320 if(nPtsForPid==3) par = fResolTPCITSDeu3;
321 if(nPtsForPid==4) par = fResolTPCITSDeu4;
324 } else if(type==AliPID::kTriton){
325 if(nPtsForPid==3) par = fResolTPCITSTri3;
326 if(nPtsForPid==4) par = fResolTPCITSTri4;
330 r=fResolTPCITS[nPtsForPid];
338 //_________________________________________________________________________
339 void AliITSPIDResponse::GetITSProbabilities(Float_t mom, Double_t qclu[4], Double_t condprobfun[AliPID::kSPECIES], Bool_t isMC) const {
341 // Method to calculate PID probabilities for a single track
342 // using the likelihood method
344 const Int_t nLay = 4;
345 const Int_t nPart= 4;
347 static AliITSPidParams pars(isMC); // Pid parametrisation parameters
349 Double_t itsProb[nPart] = {1,1,1,1}; // e, p, K, pi
351 for (Int_t iLay = 0; iLay < nLay; iLay++) {
352 if (qclu[iLay] <= 50.)
355 Float_t dedx = qclu[iLay];
356 Float_t layProb = pars.GetLandauGausNorm(dedx,AliPID::kProton,mom,iLay+3);
357 itsProb[0] *= layProb;
359 layProb = pars.GetLandauGausNorm(dedx,AliPID::kKaon,mom,iLay+3);
360 itsProb[1] *= layProb;
362 layProb = pars.GetLandauGausNorm(dedx,AliPID::kPion,mom,iLay+3);
363 itsProb[2] *= layProb;
365 layProb = pars.GetLandauGausNorm(dedx,AliPID::kElectron,mom,iLay+3);
366 itsProb[3] *= layProb;
369 // Normalise probabilities
370 Double_t sumProb = 0;
371 for (Int_t iPart = 0; iPart < nPart; iPart++) {
372 sumProb += itsProb[iPart];
374 sumProb += itsProb[2]; // muon cannot be distinguished from pions
376 for (Int_t iPart = 0; iPart < nPart; iPart++) {
377 itsProb[iPart]/=sumProb;
379 condprobfun[AliPID::kElectron] = itsProb[3];
380 condprobfun[AliPID::kMuon] = itsProb[2];
381 condprobfun[AliPID::kPion] = itsProb[2];
382 condprobfun[AliPID::kKaon] = itsProb[1];
383 condprobfun[AliPID::kProton] = itsProb[0];
387 //_________________________________________________________________________
388 Double_t AliITSPIDResponse::GetNumberOfSigmas( const AliVTrack* track, AliPID::EParticleType type) const
393 UChar_t clumap=track->GetITSClusterMap();
394 Int_t nPointsForPid=0;
395 for(Int_t i=2; i<6; i++){
396 if(clumap&(1<<i)) ++nPointsForPid;
398 Float_t mom=track->P();
400 //check for ITS standalone tracks
402 if( track->GetStatus() & AliVTrack::kTPCin ) isSA=kFALSE;
404 const Float_t dEdx=track->GetITSsignal();
406 //TODO: in case of the electron, use the SA parametrisation,
407 // this needs to be changed if ITS provides a parametrisation
408 // for electrons also for ITS+TPC tracks
409 return GetNumberOfSigmas(mom,dEdx,type,nPointsForPid,isSA || (type==AliPID::kElectron));
412 //_________________________________________________________________________
413 Double_t AliITSPIDResponse::GetSignalDelta( const AliVTrack* track, AliPID::EParticleType type, Bool_t ratio/*=kFALSE*/) const
418 const Float_t mom=track->P();
419 const Double_t chargeFactor = TMath::Power(AliPID::ParticleCharge(type),2.);
421 if( track->GetStatus() & AliVTrack::kTPCin ) isSA=kFALSE;
423 const Float_t dEdx=track->GetITSsignal();
425 //TODO: in case of the electron, use the SA parametrisation,
426 // this needs to be changed if ITS provides a parametrisation
427 // for electrons also for ITS+TPC tracks
429 const Float_t bethe = Bethe(mom,AliPID::ParticleMassZ(type), isSA || (type==AliPID::kElectron))*chargeFactor;
431 Double_t delta=-9999.;
432 if (!ratio) delta=dEdx-bethe;
433 else if (bethe>1.e-20) delta=dEdx/bethe;
438 //_________________________________________________________________________
439 Int_t AliITSPIDResponse::GetParticleIdFromdEdxVsP(Float_t mom, Float_t signal, Bool_t isSA) const{
440 // method to get particle identity with simple cuts on dE/dx vs. momentum
442 Double_t massp=AliPID::ParticleMass(AliPID::kProton);
443 Double_t massk=AliPID::ParticleMass(AliPID::kKaon);
444 Double_t bethep=Bethe(mom,massp,isSA);
445 Double_t bethek=Bethe(mom,massk,isSA);
446 if(signal>(0.5*(bethep+bethek))) return AliPID::kProton;
447 Double_t masspi=AliPID::ParticleMass(AliPID::kPion);
448 Double_t bethepi=Bethe(mom,masspi,isSA);
449 if(signal>(0.5*(bethepi+bethek))) return AliPID::kKaon;
450 return AliPID::kPion;