[u/mrichter/AliRoot.git] / STEER / STEERBase / AliITSPIDResponse.cxx

/**************************************************************************
 * Copyright(c) 2005-2007, ALICE Experiment at CERN, All rights reserved. *
 *                                                                        *
 * Author: The ALICE Off-line Project.                                    *
 * Contributors are mentioned in the code where appropriate.              *
 *                                                                        *
 * Permission to use, copy, modify and distribute this software and its   *
 * documentation strictly for non-commercial purposes is hereby granted   *
 * without fee, provided that the above copyright notice appears in all   *
 * copies and that both the copyright notice and this permission notice   *
 * appear in the supporting documentation. The authors make no claims     *
 * about the suitability of this software for any purpose. It is          *
 * provided "as is" without express or implied warranty.                  *
 **************************************************************************/

/* $Id$ */

//-----------------------------------------------------------------
// ITS PID method # 1
//           Implementation of the ITS PID class
// Very naive one... Should be made better by the detector experts...
//      Origin: Iouri Belikov, CERN, Jouri.Belikov@cern.ch
//-----------------------------------------------------------------
#include "TMath.h"
#include "AliVTrack.h"
#include "AliITSPIDResponse.h"
#include "AliITSPidParams.h"
#include "AliExternalTrackParam.h"

ClassImp(AliITSPIDResponse)

AliITSPIDResponse::AliITSPIDResponse(Bool_t isMC): 
  fRes(0.13),
  fKp1(15.77),
  fKp2(4.95),
  fKp3(0.312),
  fKp4(2.14),
  fKp5(0.82)
{
  if(!isMC){
    fBBtpcits[0]=0.73;
    fBBtpcits[1]=14.68;
    fBBtpcits[2]=0.905;
    fBBtpcits[3]=1.2;
    fBBtpcits[4]=6.6;
    fBBsa[0]=2.73198E7; //pure PHOBOS parameterization
    fBBsa[1]=6.92389;
    fBBsa[2]=1.90088E-6;
    fBBsa[3]=1.90088E-6;
    fBBsa[4]=3.40644E-7;
    fBBsaHybrid[0]=1.43505E7;  //PHOBOS+Polinomial parameterization
    fBBsaHybrid[1]=49.3402;
    fBBsaHybrid[2]=1.77741E-7;
    fBBsaHybrid[3]=1.77741E-7;
    fBBsaHybrid[4]=1.01311E-7;
    fBBsaHybrid[5]=77.2777;
    fBBsaHybrid[6]=33.4099;
    fBBsaHybrid[7]=46.0089;
    fBBsaHybrid[8]=-2.26583;
    fBBsaElectron[0]=4.05799E6;  //electrons in the ITS
    fBBsaElectron[1]=38.5713;
    fBBsaElectron[2]=1.46462E-7;
    fBBsaElectron[3]=1.46462E-7;
    fBBsaElectron[4]=4.40284E-7; 
    fResolSA[0]=1.;   // 0 cluster tracks should not be used
    fResolSA[1]=0.25;  // rough values for tracks with 1
    fResolSA[2]=0.131;   // value from pp 2010 run (L. Milano, 16-Jun-11)
    fResolSA[3]=0.113; // value from pp 2010 run 
    fResolSA[4]=0.104; // value from pp 2010 run
    for(Int_t i=0; i<5;i++) fResolTPCITS[i]=0.13;
  }else{
    fBBtpcits[0]=1.04;
    fBBtpcits[1]=27.14;
    fBBtpcits[2]=1.00;
    fBBtpcits[3]=0.964;
    fBBtpcits[4]=2.59;
    fBBsa[0]=2.02078E7; //pure PHOBOS parameterization
    fBBsa[1]=14.0724;
    fBBsa[2]=3.84454E-7;
    fBBsa[3]=3.84454E-7;
    fBBsa[4]=2.43913E-7;
    fBBsaHybrid[0]=1.05381E7; //PHOBOS+Polinomial parameterization
    fBBsaHybrid[1]=89.3933;
    fBBsaHybrid[2]=2.4831E-7;
    fBBsaHybrid[3]=2.4831E-7;
    fBBsaHybrid[4]=7.80591E-8;
    fBBsaHybrid[5]=62.9214;
    fBBsaHybrid[6]=32.347;
    fBBsaHybrid[7]=58.7661;
    fBBsaHybrid[8]=-3.39869;
    fBBsaElectron[0]=2.26807E6; //electrons in the ITS
    fBBsaElectron[1]=99.985;
    fBBsaElectron[2]=0.000714841;
    fBBsaElectron[3]=0.000259585;
    fBBsaElectron[4]=1.39412E-7;
    fResolSA[0]=1.;   // 0 cluster tracks should not be used
    fResolSA[1]=0.25;  // rough values for tracks with 1
    fResolSA[2]=0.126;   // value from pp 2010 simulations (L. Milano, 16-Jun-11)
    fResolSA[3]=0.109; // value from pp 2010 simulations
    fResolSA[4]=0.097; // value from pp 2010 simulations
    for(Int_t i=0; i<5;i++) fResolTPCITS[i]=0.13;
  }
}

/*
//_________________________________________________________________________
AliITSPIDResponse::AliITSPIDResponse(Double_t *param): 
  fRes(param[0]),
  fKp1(15.77),
  fKp2(4.95),
  fKp3(0.312),
  fKp4(2.14),
  fKp5(0.82)
{
  //
  //  The main constructor
  //
  for (Int_t i=0; i<5;i++) {
      fBBsa[i]=0.; 
      fBBtpcits[i]=0.;
      fResolSA[i]=0.; 
      fResolTPCITS[i]=0.;
  }
}
*/

//_________________________________________________________________________
Double_t AliITSPIDResponse::BetheAleph(Double_t p, Double_t mass) const {
  //
  // returns AliExternalTrackParam::BetheBloch normalized to 
  // fgMIP at the minimum
  //
  
  Double_t bb=
    AliExternalTrackParam::BetheBlochAleph(p/mass,fKp1,fKp2,fKp3,fKp4,fKp5);
  return bb;
}

//_________________________________________________________________________
Double_t AliITSPIDResponse::Bethe(Double_t p, Double_t mass, Bool_t isSA) const {
  //
  // returns AliExternalTrackParam::BetheBloch normalized to 
  // fgMIP at the minimum
  //

  Double_t bg=p/mass;
  Double_t beta = bg/TMath::Sqrt(1.+ bg*bg);
  Double_t gamma=bg/beta;
  Double_t bb=1.;
  
  Double_t par[5];
  if(isSA){
    if(mass>0.0005 && mass<0.00052){
      //if is an electron use a specific BB parameterization
      //To be used only between 100 and 160 MeV/c
      for(Int_t ip=0; ip<5;ip++) par[ip]=fBBsaElectron[ip];
    }else{
      for(Int_t ip=0; ip<5;ip++) par[ip]=fBBsa[ip];
    }
  }else{
    for(Int_t ip=0; ip<5;ip++) par[ip]=fBBtpcits[ip];
  }
  Double_t eff=1.0;
  if(bg<par[2])
    eff=(bg-par[3])*(bg-par[3])+par[4];
  else
    eff=(par[2]-par[3])*(par[2]-par[3])+par[4];
  
  if(gamma>=0. && beta>0.){
    bb=(par[1]+2.0*TMath::Log(gamma)-beta*beta)*(par[0]/(beta*beta))*eff;
  }
  return bb;
}

//_________________________________________________________________________
Double_t AliITSPIDResponse::BetheITSsaHybrid(Double_t p, Double_t mass) const {
  //
  // returns AliExternalTrackParam::BetheBloch normalized to 
  // fgMIP at the minimum. The PHOBOS parameterization is used for beta*gamma>0.76. 
  // For beta*gamma<0.76 a polinomial function is used
  
  Double_t bg=p/mass;
  Double_t beta = bg/TMath::Sqrt(1.+ bg*bg);
  Double_t gamma=bg/beta;
  Double_t bb=1.;
  
  Double_t par[9];
  //parameters for pi, K, p
  for(Int_t ip=0; ip<9;ip++) par[ip]=fBBsaHybrid[ip];
  //if it is an electron the PHOBOS part of the parameterization is tuned for e
  //in the range used for identification beta*gamma is >0.76 for electrons
  //To be used only between 100 and 160 MeV/c
  if(mass>0.0005 && mass<0.00052)for(Int_t ip=0; ip<5;ip++) par[ip]=fBBsaElectron[ip]; 
  
  if(gamma>=0. && beta>0. && bg>0.1){
    if(bg>0.76){//PHOBOS
      Double_t eff=1.0;
      if(bg<par[2])
	eff=(bg-par[3])*(bg-par[3])+par[4];
      else
	eff=(par[2]-par[3])*(par[2]-par[3])+par[4];
      
      bb=(par[1]+2.0*TMath::Log(gamma)-beta*beta)*(par[0]/(beta*beta))*eff;
    }else{//Polinomial
      bb=par[5] + par[6]/bg + par[7]/(bg*bg) + par[8]/(bg*bg*bg);
    }
  }
  return bb; 
}

//_________________________________________________________________________
Double_t AliITSPIDResponse::GetResolution(Double_t bethe, 
					  Int_t nPtsForPid, 
					  Bool_t isSA) const {
  // 
  // Calculate expected resolution for truncated mean
  //
  Float_t r;
  if(isSA) r=fResolSA[nPtsForPid];
  else r=fResolTPCITS[nPtsForPid];
  return r*bethe;
}


//_________________________________________________________________________
void AliITSPIDResponse::GetITSProbabilities(Float_t mom, Double_t qclu[4], Double_t condprobfun[AliPID::kSPECIES], Bool_t isMC) const {
  //
  // Method to calculate PID probabilities for a single track
  // using the likelihood method
  //
  const Int_t nLay = 4;
  const Int_t nPart= 4;

  static AliITSPidParams pars(isMC);  // Pid parametrisation parameters
  
  Double_t itsProb[nPart] = {1,1,1,1}; // e, p, K, pi

  for (Int_t iLay = 0; iLay < nLay; iLay++) {
    if (qclu[iLay] <= 50.)
      continue;

    Float_t dedx = qclu[iLay];
    Float_t layProb = pars.GetLandauGausNorm(dedx,AliPID::kProton,mom,iLay+3);
    itsProb[0] *= layProb;
    
    layProb = pars.GetLandauGausNorm(dedx,AliPID::kKaon,mom,iLay+3);
    itsProb[1] *= layProb;
    
    layProb = pars.GetLandauGausNorm(dedx,AliPID::kPion,mom,iLay+3);
    itsProb[2] *= layProb;
   
    layProb = pars.GetLandauGausNorm(dedx,AliPID::kElectron,mom,iLay+3);
    itsProb[3] *= layProb;
  }

  // Normalise probabilities
  Double_t sumProb = 0;
  for (Int_t iPart = 0; iPart < nPart; iPart++) {
    sumProb += itsProb[iPart];
  }
  sumProb += itsProb[2]; // muon cannot be distinguished from pions

  for (Int_t iPart = 0; iPart < nPart; iPart++) {
    itsProb[iPart]/=sumProb;
  }
  condprobfun[AliPID::kElectron] = itsProb[3];
  condprobfun[AliPID::kMuon] = itsProb[2];
  condprobfun[AliPID::kPion] = itsProb[2];
  condprobfun[AliPID::kKaon] = itsProb[1];
  condprobfun[AliPID::kProton] = itsProb[0];
  return;
}

//_________________________________________________________________________
Double_t AliITSPIDResponse::GetNumberOfSigmas( const AliVTrack* track, AliPID::EParticleType type) const
{
  //
  // number of sigmas
  //
  UChar_t clumap=track->GetITSClusterMap();
  Int_t nPointsForPid=0;
  for(Int_t i=2; i<6; i++){
    if(clumap&(1<<i)) ++nPointsForPid;
  }
  Float_t mom=track->P();
  
  //check for ITS standalone tracks
  Bool_t isSA=kTRUE;
  if( track->GetStatus() & AliVTrack::kTPCin ) isSA=kFALSE;
  
  const Float_t dEdx=track->GetITSsignal();
  
  //TODO: in case of the electron, use the SA parametrisation,
  //      this needs to be changed if ITS provides a parametrisation
  //      for electrons also for ITS+TPC tracks
  return GetNumberOfSigmas(mom,dEdx,type,nPointsForPid,isSA || (type==AliPID::kElectron));
}

//_________________________________________________________________________
Double_t AliITSPIDResponse::GetSignalDelta( const AliVTrack* track, AliPID::EParticleType type, Bool_t ratio/*=kFALSE*/) const
{
  //
  // Signal - expected
  //
  const Float_t mom=track->P();
  const Double_t chargeFactor = TMath::Power(AliPID::ParticleCharge(type),2.);
  Bool_t isSA=kTRUE;
  if( track->GetStatus() & AliVTrack::kTPCin ) isSA=kFALSE;
  
  const Float_t dEdx=track->GetITSsignal();
  
  //TODO: in case of the electron, use the SA parametrisation,
  //      this needs to be changed if ITS provides a parametrisation
  //      for electrons also for ITS+TPC tracks
  
  const Float_t bethe = Bethe(mom,AliPID::ParticleMassZ(type), isSA || (type==AliPID::kElectron))*chargeFactor;

  Double_t delta=-9999.;
  if (!ratio) delta=dEdx-bethe;
  else if (bethe>1.e-20) delta=dEdx/bethe;
  
  return delta;
}

//_________________________________________________________________________
Int_t AliITSPIDResponse::GetParticleIdFromdEdxVsP(Float_t mom, Float_t signal, Bool_t isSA) const{
  // method to get particle identity with simple cuts on dE/dx vs. momentum

  Double_t massp=AliPID::ParticleMass(AliPID::kProton);
  Double_t massk=AliPID::ParticleMass(AliPID::kKaon);
  Double_t bethep=Bethe(mom,massp,isSA);
  Double_t bethek=Bethe(mom,massk,isSA);
  if(signal>(0.5*(bethep+bethek))) return AliPID::kProton;
  Double_t masspi=AliPID::ParticleMass(AliPID::kPion);
  Double_t bethepi=Bethe(mom,masspi,isSA);
  if(signal>(0.5*(bethepi+bethek))) return AliPID::kKaon;
  return AliPID::kPion;
    
}
Commit	Line	Data
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"
567624b5	25	#include "AliVTrack.h"
10d100d4	26	#include "AliITSPIDResponse.h"
	27	#include "AliITSPidParams.h"
	28	#include "AliExternalTrackParam.h"
	29
10d100d4	30	ClassImp(AliITSPIDResponse)
10d100d4	31
15e979c9	32	AliITSPIDResponse::AliITSPIDResponse(Bool_t isMC):
10d100d4	33	fRes(0.13),
	34	fKp1(15.77),
	35	fKp2(4.95),
	36	fKp3(0.312),
	37	fKp4(2.14),
	38	fKp5(0.82)
	39	{
15e979c9	40	if(!isMC){
	41	fBBtpcits[0]=0.73;
	42	fBBtpcits[1]=14.68;
	43	fBBtpcits[2]=0.905;
	44	fBBtpcits[3]=1.2;
	45	fBBtpcits[4]=6.6;
62ccfebf	46	fBBsa[0]=2.73198E7; //pure PHOBOS parameterization
88f46717	47	fBBsa[1]=6.92389;
	48	fBBsa[2]=1.90088E-6;
	49	fBBsa[3]=1.90088E-6;
	50	fBBsa[4]=3.40644E-7;
62ccfebf	51	fBBsaHybrid[0]=1.43505E7; //PHOBOS+Polinomial parameterization
	52	fBBsaHybrid[1]=49.3402;
	53	fBBsaHybrid[2]=1.77741E-7;
	54	fBBsaHybrid[3]=1.77741E-7;
	55	fBBsaHybrid[4]=1.01311E-7;
	56	fBBsaHybrid[5]=77.2777;
	57	fBBsaHybrid[6]=33.4099;
	58	fBBsaHybrid[7]=46.0089;
	59	fBBsaHybrid[8]=-2.26583;
	60	fBBsaElectron[0]=4.05799E6; //electrons in the ITS
88f46717	61	fBBsaElectron[1]=38.5713;
	62	fBBsaElectron[2]=1.46462E-7;
	63	fBBsaElectron[3]=1.46462E-7;
	64	fBBsaElectron[4]=4.40284E-7;
8abeb05b	65	fResolSA[0]=1.; // 0 cluster tracks should not be used
88f46717	66	fResolSA[1]=0.25; // rough values for tracks with 1
	67	fResolSA[2]=0.131; // value from pp 2010 run (L. Milano, 16-Jun-11)
	68	fResolSA[3]=0.113; // value from pp 2010 run
8abeb05b	69	fResolSA[4]=0.104; // value from pp 2010 run
15e979c9	70	for(Int_t i=0; i<5;i++) fResolTPCITS[i]=0.13;
15e979c9	71	}else{
99daa709	72	fBBtpcits[0]=1.04;
	73	fBBtpcits[1]=27.14;
	74	fBBtpcits[2]=1.00;
	75	fBBtpcits[3]=0.964;
	76	fBBtpcits[4]=2.59;
62ccfebf	77	fBBsa[0]=2.02078E7; //pure PHOBOS parameterization
88f46717	78	fBBsa[1]=14.0724;
	79	fBBsa[2]=3.84454E-7;
	80	fBBsa[3]=3.84454E-7;
	81	fBBsa[4]=2.43913E-7;
62ccfebf	82	fBBsaHybrid[0]=1.05381E7; //PHOBOS+Polinomial parameterization
	83	fBBsaHybrid[1]=89.3933;
	84	fBBsaHybrid[2]=2.4831E-7;
	85	fBBsaHybrid[3]=2.4831E-7;
	86	fBBsaHybrid[4]=7.80591E-8;
	87	fBBsaHybrid[5]=62.9214;
	88	fBBsaHybrid[6]=32.347;
	89	fBBsaHybrid[7]=58.7661;
	90	fBBsaHybrid[8]=-3.39869;
	91	fBBsaElectron[0]=2.26807E6; //electrons in the ITS
88f46717	92	fBBsaElectron[1]=99.985;
	93	fBBsaElectron[2]=0.000714841;
	94	fBBsaElectron[3]=0.000259585;
	95	fBBsaElectron[4]=1.39412E-7;
8abeb05b	96	fResolSA[0]=1.; // 0 cluster tracks should not be used
88f46717	97	fResolSA[1]=0.25; // rough values for tracks with 1
	98	fResolSA[2]=0.126; // value from pp 2010 simulations (L. Milano, 16-Jun-11)
	99	fResolSA[3]=0.109; // value from pp 2010 simulations
	100	fResolSA[4]=0.097; // value from pp 2010 simulations
15e979c9	101	for(Int_t i=0; i<5;i++) fResolTPCITS[i]=0.13;
15e979c9	102	}
10d100d4	103	}
10d100d4	104
56576f1e	105	/*
10d100d4	106	//_________________________________________________________________________
10d100d4	107	AliITSPIDResponse::AliITSPIDResponse(Double_t *param):
9ebbddd4	108	fRes(param[0]),
10d100d4	109	fKp1(15.77),
	110	fKp2(4.95),
	111	fKp3(0.312),
	112	fKp4(2.14),
	113	fKp5(0.82)
	114	{
	115	//
	116	// The main constructor
	117	//
6b4634a4	118	for (Int_t i=0; i<5;i++) {
	119	fBBsa[i]=0.;
	120	fBBtpcits[i]=0.;
	121	fResolSA[i]=0.;
	122	fResolTPCITS[i]=0.;
	123	}
10d100d4	124	}
56576f1e	125	*/
10d100d4	126
8abeb05b	127	//_________________________________________________________________________
15e979c9	128	Double_t AliITSPIDResponse::BetheAleph(Double_t p, Double_t mass) const {
10d100d4	129	//
	130	// returns AliExternalTrackParam::BetheBloch normalized to
	131	// fgMIP at the minimum
	132	//
15e979c9	133
10d100d4	134	Double_t bb=
10d100d4	135	AliExternalTrackParam::BetheBlochAleph(p/mass,fKp1,fKp2,fKp3,fKp4,fKp5);
9ebbddd4	136	return bb;
10d100d4	137	}
10d100d4	138
8abeb05b	139	//_________________________________________________________________________
15e979c9	140	Double_t AliITSPIDResponse::Bethe(Double_t p, Double_t mass, Bool_t isSA) const {
	141	//
	142	// returns AliExternalTrackParam::BetheBloch normalized to
	143	// fgMIP at the minimum
	144	//
	145
	146	Double_t bg=p/mass;
	147	Double_t beta = bg/TMath::Sqrt(1.+ bg*bg);
	148	Double_t gamma=bg/beta;
62ccfebf	149	Double_t bb=1.;
62ccfebf	150
15e979c9	151	Double_t par[5];
15e979c9	152	if(isSA){
88f46717	153	if(mass>0.0005 && mass<0.00052){
	154	//if is an electron use a specific BB parameterization
	155	//To be used only between 100 and 160 MeV/c
	156	for(Int_t ip=0; ip<5;ip++) par[ip]=fBBsaElectron[ip];
	157	}else{
	158	for(Int_t ip=0; ip<5;ip++) par[ip]=fBBsa[ip];
	159	}
15e979c9	160	}else{
	161	for(Int_t ip=0; ip<5;ip++) par[ip]=fBBtpcits[ip];
	162	}
	163	Double_t eff=1.0;
	164	if(bg<par[2])
	165	eff=(bg-par[3])*(bg-par[3])+par[4];
	166	else
	167	eff=(par[2]-par[3])*(par[2]-par[3])+par[4];
88f46717	168
15e979c9	169	if(gamma>=0. && beta>0.){
	170	bb=(par[1]+2.0TMath::Log(gamma)-betabeta)(par[0]/(betabeta))*eff;
	171	}
	172	return bb;
	173	}
	174
62ccfebf	175	//_________________________________________________________________________
	176	Double_t AliITSPIDResponse::BetheITSsaHybrid(Double_t p, Double_t mass) const {
	177	//
	178	// returns AliExternalTrackParam::BetheBloch normalized to
	179	// fgMIP at the minimum. The PHOBOS parameterization is used for beta*gamma>0.76.
	180	// For beta*gamma<0.76 a polinomial function is used
	181
	182	Double_t bg=p/mass;
	183	Double_t beta = bg/TMath::Sqrt(1.+ bg*bg);
	184	Double_t gamma=bg/beta;
	185	Double_t bb=1.;
	186
	187	Double_t par[9];
	188	//parameters for pi, K, p
	189	for(Int_t ip=0; ip<9;ip++) par[ip]=fBBsaHybrid[ip];
	190	//if it is an electron the PHOBOS part of the parameterization is tuned for e
	191	//in the range used for identification beta*gamma is >0.76 for electrons
	192	//To be used only between 100 and 160 MeV/c
	193	if(mass>0.0005 && mass<0.00052)for(Int_t ip=0; ip<5;ip++) par[ip]=fBBsaElectron[ip];
	194
	195	if(gamma>=0. && beta>0. && bg>0.1){
	196	if(bg>0.76){//PHOBOS
	197	Double_t eff=1.0;
	198	if(bg<par[2])
	199	eff=(bg-par[3])*(bg-par[3])+par[4];
	200	else
	201	eff=(par[2]-par[3])*(par[2]-par[3])+par[4];
	202
	203	bb=(par[1]+2.0TMath::Log(gamma)-betabeta)(par[0]/(betabeta))*eff;
	204	}else{//Polinomial
	205	bb=par[5] + par[6]/bg + par[7]/(bgbg) + par[8]/(bgbg*bg);
	206	}
	207	}
	208	return bb;
	209	}
	210
8abeb05b	211	//_________________________________________________________________________
15e979c9	212	Double_t AliITSPIDResponse::GetResolution(Double_t bethe,
	213	Int_t nPtsForPid,
	214	Bool_t isSA) const {
10d100d4	215	//
	216	// Calculate expected resolution for truncated mean
	217	//
15e979c9	218	Float_t r;
	219	if(isSA) r=fResolSA[nPtsForPid];
	220	else r=fResolTPCITS[nPtsForPid];
	221	return r*bethe;
10d100d4	222	}
10d100d4	223
15e979c9	224
	225
	226
8abeb05b	227	//_________________________________________________________________________
b52bfc67	228	void AliITSPIDResponse::GetITSProbabilities(Float_t mom, Double_t qclu[4], Double_t condprobfun[AliPID::kSPECIES], Bool_t isMC) const {
10d100d4	229	//
	230	// Method to calculate PID probabilities for a single track
	231	// using the likelihood method
	232	//
	233	const Int_t nLay = 4;
2ca1f4ee	234	const Int_t nPart= 4;
10d100d4	235
b52bfc67	236	static AliITSPidParams pars(isMC); // Pid parametrisation parameters
10d100d4	237
2ca1f4ee	238	Double_t itsProb[nPart] = {1,1,1,1}; // e, p, K, pi
10d100d4	239
10d100d4	240	for (Int_t iLay = 0; iLay < nLay; iLay++) {
2ca1f4ee	241	if (qclu[iLay] <= 50.)
10d100d4	242	continue;
	243
	244	Float_t dedx = qclu[iLay];
	245	Float_t layProb = pars.GetLandauGausNorm(dedx,AliPID::kProton,mom,iLay+3);
	246	itsProb[0] *= layProb;
	247
	248	layProb = pars.GetLandauGausNorm(dedx,AliPID::kKaon,mom,iLay+3);
10d100d4	249	itsProb[1] *= layProb;
	250
	251	layProb = pars.GetLandauGausNorm(dedx,AliPID::kPion,mom,iLay+3);
	252	itsProb[2] *= layProb;
2ca1f4ee	253
	254	layProb = pars.GetLandauGausNorm(dedx,AliPID::kElectron,mom,iLay+3);
	255	itsProb[3] *= layProb;
10d100d4	256	}
	257
	258	// Normalise probabilities
	259	Double_t sumProb = 0;
	260	for (Int_t iPart = 0; iPart < nPart; iPart++) {
	261	sumProb += itsProb[iPart];
	262	}
2ca1f4ee	263	sumProb += itsProb[2]; // muon cannot be distinguished from pions
10d100d4	264
	265	for (Int_t iPart = 0; iPart < nPart; iPart++) {
	266	itsProb[iPart]/=sumProb;
	267	}
2ca1f4ee	268	condprobfun[AliPID::kElectron] = itsProb[3];
897a0e31	269	condprobfun[AliPID::kMuon] = itsProb[2];
897a0e31	270	condprobfun[AliPID::kPion] = itsProb[2];
10d100d4	271	condprobfun[AliPID::kKaon] = itsProb[1];
	272	condprobfun[AliPID::kProton] = itsProb[0];
	273	return;
	274	}
15e979c9	275
567624b5	276	//_________________________________________________________________________
	277	Double_t AliITSPIDResponse::GetNumberOfSigmas( const AliVTrack* track, AliPID::EParticleType type) const
	278	{
	279	//
	280	// number of sigmas
	281	//
	282	UChar_t clumap=track->GetITSClusterMap();
	283	Int_t nPointsForPid=0;
	284	for(Int_t i=2; i<6; i++){
	285	if(clumap&(1<<i)) ++nPointsForPid;
	286	}
	287	Float_t mom=track->P();
	288
	289	//check for ITS standalone tracks
	290	Bool_t isSA=kTRUE;
	291	if( track->GetStatus() & AliVTrack::kTPCin ) isSA=kFALSE;
	292
	293	const Float_t dEdx=track->GetITSsignal();
	294
	295	//TODO: in case of the electron, use the SA parametrisation,
	296	// this needs to be changed if ITS provides a parametrisation
	297	// for electrons also for ITS+TPC tracks
	298	return GetNumberOfSigmas(mom,dEdx,type,nPointsForPid,isSA \|\| (type==AliPID::kElectron));
	299	}
	300
	301	//_________________________________________________________________________
1d59271b	302	Double_t AliITSPIDResponse::GetSignalDelta( const AliVTrack* track, AliPID::EParticleType type, Bool_t ratio/=kFALSE/) const
567624b5	303	{
	304	//
	305	// Signal - expected
	306	//
	307	const Float_t mom=track->P();
	308	const Double_t chargeFactor = TMath::Power(AliPID::ParticleCharge(type),2.);
	309	Bool_t isSA=kTRUE;
	310	if( track->GetStatus() & AliVTrack::kTPCin ) isSA=kFALSE;
	311
	312	const Float_t dEdx=track->GetITSsignal();
	313
	314	//TODO: in case of the electron, use the SA parametrisation,
	315	// this needs to be changed if ITS provides a parametrisation
	316	// for electrons also for ITS+TPC tracks
	317
1d59271b	318	const Float_t bethe = Bethe(mom,AliPID::ParticleMassZ(type), isSA \|\| (type==AliPID::kElectron))*chargeFactor;
	319
	320	Double_t delta=-9999.;
	321	if (!ratio) delta=dEdx-bethe;
	322	else if (bethe>1.e-20) delta=dEdx/bethe;
	323
	324	return delta;
567624b5	325	}
567624b5	326
8abeb05b	327	//_________________________________________________________________________
	328	Int_t AliITSPIDResponse::GetParticleIdFromdEdxVsP(Float_t mom, Float_t signal, Bool_t isSA) const{
	329	// method to get particle identity with simple cuts on dE/dx vs. momentum
	330
	331	Double_t massp=AliPID::ParticleMass(AliPID::kProton);
	332	Double_t massk=AliPID::ParticleMass(AliPID::kKaon);
	333	Double_t bethep=Bethe(mom,massp,isSA);
	334	Double_t bethek=Bethe(mom,massk,isSA);
	335	if(signal>(0.5*(bethep+bethek))) return AliPID::kProton;
	336	Double_t masspi=AliPID::ParticleMass(AliPID::kPion);
	337	Double_t bethepi=Bethe(mom,masspi,isSA);
	338	if(signal>(0.5*(bethepi+bethek))) return AliPID::kKaon;
	339	return AliPID::kPion;
	340
	341	}