HMPID/AliHMPIDPid.cxx

   1 /**************************************************************************
   2  * Copyright(c) 1998-1999, 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 //////////////////////////////////////////////////////////////////////////
  17 //                                                                      //
  18 // AliHMPIDPid                                                          //
  19 //                                                                      //
  20 // HMPID class to perfom particle identification                        //
  21 //                                                                      //
  22 //////////////////////////////////////////////////////////////////////////
  23
  24 #include "AliHMPIDPid.h"       //class header
  25 #include "AliHMPIDParam.h"     //class header
  26 #include <AliESDtrack.h>       //FindPid()
  27
  28 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  29 AliHMPIDPid::AliHMPIDPid():TTask("HMPIDrec","HMPIDPid")
  30 {
  31 //..
  32 //init of data members
  33 //..
  34 }
  35 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  36 void AliHMPIDPid::FindPid(AliESDtrack *pTrk,Int_t nsp,Double_t *prob)
  37 {
  38 // Calculates probability to be a electron-muon-pion-kaon-proton
  39 // from the given Cerenkov angle and momentum assuming no initial particle composition
  40 // (i.e. apriory probability to be the particle of the given sort is the same for all sorts)
  41
  42   if(pTrk->GetHMPIDsignal()<=0){//HMPID does not find anything reasonable for this track, assign 0.2 for all species
  43     for(Int_t iPart=0;iPart<nsp;iPart++) prob[iPart]=1.0/(Float_t)nsp;
  44     return;
  45   }
  46
  47   Double_t pmod = pTrk->GetP();
  48   Double_t hTot=0;
  49   Double_t *h = new Double_t [nsp];
  50
  51   for(Int_t iPart=0;iPart<nsp;iPart++){
  52     Double_t mass = AliPID::ParticleMass(iPart);
  53     Double_t cosThetaTh = TMath::Sqrt(mass*mass+pmod*pmod)/(AliHMPIDParam::Instance()->MeanIdxRad()*pmod);
  54     if(cosThetaTh<1) //calculate the height of theoretical theta ckov on the gaus of experimental one
  55       h[iPart] =TMath::Gaus(TMath::ACos(cosThetaTh),pTrk->GetHMPIDsignal(),TMath::Sqrt(pTrk->GetHMPIDchi2()),kTRUE);
  56     else             //beta < 1/ref. idx. => no light at all
  57       h[iPart] =0 ;
  58     hTot    +=h[iPart]; //total height of all theoretical heights for normalization
  59   }//species loop
  60
  61   Double_t hMin=TMath::Gaus(pTrk->GetHMPIDsignal()-4*TMath::Sqrt(pTrk->GetHMPIDchi2()),pTrk->GetHMPIDsignal(),TMath::Sqrt(pTrk->GetHMPIDchi2()),kTRUE);//5 sigma protection
  62
  63   for(Int_t iPart=0;iPart<nsp;iPart++) {//species loop to assign probabilities
  64     if(hTot>hMin) prob[iPart]=h[iPart]/hTot;
  65     else prob[iPart]=1.0/(Float_t)nsp;            //all theoretical values are far away from experemental one
  66   }
  67   delete [] h;
  68 }
  69 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++