[u/mrichter/AliRoot.git] / STEER / 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 "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]=5.33458E4;
    fBBsa[1]=16.5303;
    fBBsa[2]=2.60065E-3;
    fBBsa[3]=3.59533E-4;
    fBBsa[4]=7.51168E-5;  
    fResolSA[0]=1.;   // 0 cluster tracks should not be used
    fResolSA[1]=0.25;  // rough values for tracks with 1 or 2
    fResolSA[2]=0.2;   // clusters (not to be used)
    fResolSA[3]=0.116; // value from pp 2010 run (L. Milano, 18-Jan-11)
    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]=-2.48;
    fBBsa[1]=23.13;
    fBBsa[2]=1.161;
    fBBsa[3]=0.93;
    fBBsa[4]=-1.2973;
    fResolSA[0]=1.;   // 0 cluster tracks should not be used
    fResolSA[1]=0.25;  // rough values for tracks with 1 or 2
    fResolSA[2]=0.2;   // clusters (not to be used)
    fResolSA[3]=0.110; // value from pp 2010 simulations (L. Milano, 18-Jan-11)
    fResolSA[4]=0.096; // 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
  //
}


//_________________________________________________________________________
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 par[5];
  if(isSA){
    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];

  Double_t bb=0.;
  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::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]) const {
  //
  // Method to calculate PID probabilities for a single track
  // using the likelihood method
  //
  const Int_t nLay = 4;
  const Int_t nPart = 3;

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

  for (Int_t iLay = 0; iLay < nLay; iLay++) {
    if (qclu[iLay] <= 0)
      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);
    if (mom < 0.16) layProb=0.00001;
    itsProb[1] *= layProb;
    
    layProb = pars.GetLandauGausNorm(dedx,AliPID::kPion,mom,iLay+3);
    itsProb[2] *= layProb;
  }

  // Normalise probabilities
  Double_t sumProb = 0;
  for (Int_t iPart = 0; iPart < nPart; iPart++) {
    sumProb += itsProb[iPart];
  }

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

//_________________________________________________________________________
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"
	25	#include "AliITSPIDResponse.h"
	26	#include "AliITSPidParams.h"
	27	#include "AliExternalTrackParam.h"
	28
10d100d4	29	ClassImp(AliITSPIDResponse)
10d100d4	30
15e979c9	31	AliITSPIDResponse::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;
8abeb05b	50	fResolSA[0]=1.; // 0 cluster tracks should not be used
	51	fResolSA[1]=0.25; // rough values for tracks with 1 or 2
	52	fResolSA[2]=0.2; // clusters (not to be used)
	53	fResolSA[3]=0.116; // value from pp 2010 run (L. Milano, 18-Jan-11)
	54	fResolSA[4]=0.104; // value from pp 2010 run
15e979c9	55	for(Int_t i=0; i<5;i++) fResolTPCITS[i]=0.13;
15e979c9	56	}else{
99daa709	57	fBBtpcits[0]=1.04;
	58	fBBtpcits[1]=27.14;
	59	fBBtpcits[2]=1.00;
	60	fBBtpcits[3]=0.964;
	61	fBBtpcits[4]=2.59;
646e694f	62	fBBsa[0]=-2.48;
	63	fBBsa[1]=23.13;
	64	fBBsa[2]=1.161;
	65	fBBsa[3]=0.93;
	66	fBBsa[4]=-1.2973;
8abeb05b	67	fResolSA[0]=1.; // 0 cluster tracks should not be used
	68	fResolSA[1]=0.25; // rough values for tracks with 1 or 2
	69	fResolSA[2]=0.2; // clusters (not to be used)
	70	fResolSA[3]=0.110; // value from pp 2010 simulations (L. Milano, 18-Jan-11)
	71	fResolSA[4]=0.096; // value from pp 2010 simulations
15e979c9	72	for(Int_t i=0; i<5;i++) fResolTPCITS[i]=0.13;
15e979c9	73	}
10d100d4	74	}
	75
	76	//_________________________________________________________________________
	77	AliITSPIDResponse::AliITSPIDResponse(Double_t *param):
9ebbddd4	78	fRes(param[0]),
10d100d4	79	fKp1(15.77),
	80	fKp2(4.95),
	81	fKp3(0.312),
	82	fKp4(2.14),
	83	fKp5(0.82)
	84	{
	85	//
	86	// The main constructor
	87	//
10d100d4	88	}
	89
	90
8abeb05b	91	//_________________________________________________________________________
15e979c9	92	Double_t AliITSPIDResponse::BetheAleph(Double_t p, Double_t mass) const {
10d100d4	93	//
	94	// returns AliExternalTrackParam::BetheBloch normalized to
	95	// fgMIP at the minimum
	96	//
15e979c9	97
10d100d4	98	Double_t bb=
10d100d4	99	AliExternalTrackParam::BetheBlochAleph(p/mass,fKp1,fKp2,fKp3,fKp4,fKp5);
9ebbddd4	100	return bb;
10d100d4	101	}
10d100d4	102
8abeb05b	103	//_________________________________________________________________________
15e979c9	104	Double_t AliITSPIDResponse::Bethe(Double_t p, Double_t mass, Bool_t isSA) const {
	105	//
	106	// returns AliExternalTrackParam::BetheBloch normalized to
	107	// fgMIP at the minimum
	108	//
	109
	110	Double_t bg=p/mass;
	111	Double_t beta = bg/TMath::Sqrt(1.+ bg*bg);
	112	Double_t gamma=bg/beta;
	113	Double_t par[5];
	114	if(isSA){
	115	for(Int_t ip=0; ip<5;ip++) par[ip]=fBBsa[ip];
	116	}else{
	117	for(Int_t ip=0; ip<5;ip++) par[ip]=fBBtpcits[ip];
	118	}
	119	Double_t eff=1.0;
	120	if(bg<par[2])
	121	eff=(bg-par[3])*(bg-par[3])+par[4];
	122	else
	123	eff=(par[2]-par[3])*(par[2]-par[3])+par[4];
	124
	125	Double_t bb=0.;
	126	if(gamma>=0. && beta>0.){
	127	bb=(par[1]+2.0TMath::Log(gamma)-betabeta)(par[0]/(betabeta))*eff;
	128	}
	129	return bb;
	130	}
	131
8abeb05b	132	//_________________________________________________________________________
15e979c9	133	Double_t AliITSPIDResponse::GetResolution(Double_t bethe,
	134	Int_t nPtsForPid,
	135	Bool_t isSA) const {
10d100d4	136	//
	137	// Calculate expected resolution for truncated mean
	138	//
15e979c9	139	Float_t r;
	140	if(isSA) r=fResolSA[nPtsForPid];
	141	else r=fResolTPCITS[nPtsForPid];
	142	return r*bethe;
10d100d4	143	}
10d100d4	144
15e979c9	145
	146
	147
8abeb05b	148	//_________________________________________________________________________
10d100d4	149	void AliITSPIDResponse::GetITSProbabilities(Float_t mom, Double_t qclu[4], Double_t condprobfun[AliPID::kSPECIES]) const {
	150	//
	151	// Method to calculate PID probabilities for a single track
	152	// using the likelihood method
	153	//
	154	const Int_t nLay = 4;
	155	const Int_t nPart = 3;
	156
	157	static AliITSPidParams pars; // Pid parametrisation parameters
	158
	159	Double_t itsProb[nPart] = {1,1,1}; // p, K, pi
	160
	161	for (Int_t iLay = 0; iLay < nLay; iLay++) {
	162	if (qclu[iLay] <= 0)
	163	continue;
	164
	165	Float_t dedx = qclu[iLay];
	166	Float_t layProb = pars.GetLandauGausNorm(dedx,AliPID::kProton,mom,iLay+3);
	167	itsProb[0] *= layProb;
	168
	169	layProb = pars.GetLandauGausNorm(dedx,AliPID::kKaon,mom,iLay+3);
	170	if (mom < 0.16) layProb=0.00001;
	171	itsProb[1] *= layProb;
	172
	173	layProb = pars.GetLandauGausNorm(dedx,AliPID::kPion,mom,iLay+3);
	174	itsProb[2] *= layProb;
	175	}
	176
	177	// Normalise probabilities
	178	Double_t sumProb = 0;
	179	for (Int_t iPart = 0; iPart < nPart; iPart++) {
	180	sumProb += itsProb[iPart];
	181	}
	182
	183	for (Int_t iPart = 0; iPart < nPart; iPart++) {
	184	itsProb[iPart]/=sumProb;
	185	}
	186
	187	condprobfun[AliPID::kElectron] = itsProb[2]/3.;
	188	condprobfun[AliPID::kMuon] = itsProb[2]/3.;
	189	condprobfun[AliPID::kPion] = itsProb[2]/3.;
	190	condprobfun[AliPID::kKaon] = itsProb[1];
	191	condprobfun[AliPID::kProton] = itsProb[0];
	192	return;
	193	}
15e979c9	194
8abeb05b	195	//_________________________________________________________________________
	196	Int_t AliITSPIDResponse::GetParticleIdFromdEdxVsP(Float_t mom, Float_t signal, Bool_t isSA) const{
	197	// method to get particle identity with simple cuts on dE/dx vs. momentum
	198
	199	Double_t massp=AliPID::ParticleMass(AliPID::kProton);
	200	Double_t massk=AliPID::ParticleMass(AliPID::kKaon);
	201	Double_t bethep=Bethe(mom,massp,isSA);
	202	Double_t bethek=Bethe(mom,massk,isSA);
	203	if(signal>(0.5*(bethep+bethek))) return AliPID::kProton;
	204	Double_t masspi=AliPID::ParticleMass(AliPID::kPion);
	205	Double_t bethepi=Bethe(mom,masspi,isSA);
	206	if(signal>(0.5*(bethepi+bethek))) return AliPID::kKaon;
	207	return AliPID::kPion;
	208
	209	}