Removing wide clusters from the reconstruction (M.Ivanov)

[u/mrichter/AliRoot.git] / TRD / AliTRDpidESD.cxx

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 * Author: The ALICE Off-line Project.                                    *
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 * about the suitability of this software for any purpose. It is          *
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//-----------------------------------------------------------------
//           Implementation of the TRD PID class
// Assigns the electron and pion liklihoods for each ESD track.
// The AliTRDprobdist class is instantiated here.
// The function MakePID(AliESD *event) calculates the probability
// of having dedx and the probability of having timbin at a given 
// momentum (mom) and particle type k (0 for e) and (2 for pi)
// from the precalculated timbin distributions. 
// Prashant Shukla <shukla@pi0.physi.uni-heidelberg.de>
//-----------------------------------------------------------------

#include "AliTRDpidESD.h"
#include "AliESD.h"
#include "AliESDtrack.h"
#include "AliTRDprobdist.h"

ClassImp(AliTRDpidESD)

//_________________________________________________________________________
AliTRDpidESD::AliTRDpidESD(Double_t *param)
{
  //
  //  The main constructor
  //
  fMIP=param[0];   // MIP signal
  fRes=param[1];   // relative resolution
  fRange=param[2]; // PID "range" (in sigmas)
}

Double_t AliTRDpidESD::Bethe(Double_t bg) 
{
  //
  // Parametrization of the Bethe-Bloch-curve
  // The parametrization is the same as for the TPC and is taken from Lehrhaus.
  //

  // This parameters have been adjusted to averaged values from GEANT
  const Double_t kP1 = 7.17960e-02;
  const Double_t kP2 = 8.54196;
  const Double_t kP3 = 1.38065e-06;
  const Double_t kP4 = 5.30972;
  const Double_t kP5 = 2.83798;

  // This parameters have been adjusted to Xe-data found in:
  // Allison & Cobb, Ann. Rev. Nucl. Sci. (1980), 30, 253
  //const Double_t kP1 = 0.76176E-1;
  //const Double_t kP2 = 10.632;
  //const Double_t kP3 = 3.17983E-6;
  //const Double_t kP4 = 1.8631;
  //const Double_t kP5 = 1.9479;

  // Lower cutoff of the Bethe-Bloch-curve to limit step sizes
  const Double_t kBgMin = 0.8;
  const Double_t kBBMax = 6.83298;
  //const Double_t kBgMin = 0.6;
  //const Double_t kBBMax = 17.2809;
  //const Double_t kBgMin = 0.4;
  //const Double_t kBBMax = 82.0;

  if (bg > kBgMin) {
    Double_t yy = bg / TMath::Sqrt(1. + bg*bg);
    Double_t aa = TMath::Power(yy,kP4);
    Double_t bb = TMath::Power((1./bg),kP5);
             bb = TMath::Log(kP3 + bb);
    return ((kP2 - aa - bb)*kP1 / aa);
  }
  else {
    return kBBMax;
  }

}

//_________________________________________________________________________
Int_t AliTRDpidESD::MakePID(AliESD *event)
{
  //
  //  This function calculates the "detector response" PID probabilities 
  //
  // The class AliTRDprobdist contains precalculated prob dis.
  AliTRDprobdist *pd = new AliTRDprobdist();
  //  Double_t ebin[200], ppi[200], pel[200];
  //  pd->GetData(2,ebin,ppi,pel);
  //  for(Int_t ie=0; ie<10; ie++)  
  //    printf(" %f %f %f \n", ebin[ie], ppi[ie], pel[ie]);

  Int_t ntrk=event->GetNumberOfTracks();
  for (Int_t i=0; i<ntrk; i++) {
    AliESDtrack *t=event->GetTrack(i);
    if ((t->GetStatus()&AliESDtrack::kTRDin)==0)
       if ((t->GetStatus()&AliESDtrack::kTRDout)==0)
          if ((t->GetStatus()&AliESDtrack::kTRDrefit)==0) continue;
    //    Int_t ns=AliESDtrack::kSPECIES;
    Int_t ns=AliPID::kSPECIES;
    Double_t p[10];
    Double_t mom=t->GetP();
    for (Int_t j=0; j<ns; j++) {
      p[j]=1.;
      for (Int_t ilayer=0; ilayer <6; ilayer++) {
        Double_t dedx=t->GetTRDsignals(ilayer);
        Int_t timbin=t->GetTRDTimBin(ilayer);
        if (j==0 || j==2){
          p[j]*= pd->GetProbability(j,mom,dedx);
          p[j]*= pd->GetProbabilityT(j,mom,timbin);
          p[j]*= 100;
        }
      } // loop over layers
    } //loop over particle species
    //    printf(" %f  %d  %f  %f  %f \n", mom, timbin, p[0], p[1], p[2]);
    if(p[0]) p[0]= p[0]/(p[0]+p[2]); 
    if(p[2]) p[2]= 1.-p[0];
    t->SetTRDpid(p);
  } //loop over track
  delete pd;
  return 0;
}


/*
//_________________________________________________________________________
MakePID(AliESD *event)
{
  //
  //  This function calculates the "detector response" PID probabilities 
  //
  Int_t ntrk=event->GetNumberOfTracks();
  for (Int_t i=0; i<ntrk; i++) {
    AliESDtrack *t=event->GetTrack(i);
    if ((t->GetStatus()&AliESDtrack::kTRDin)==0)
       if ((t->GetStatus()&AliESDtrack::kTRDout)==0)
          if ((t->GetStatus()&AliESDtrack::kTRDrefit)==0) continue;
	  //    Int_t ns=AliESDtrack::kSPECIES;
    Int_t ns=AliPID::kSPECIES;
    Double_t p[10];
    for (Int_t j=0; j<ns; j++) {
      Double_t mass=AliPID::ParticleMass(j);
      Double_t mass=masses[j];
      Double_t mom=t->GetP();
      Double_t dedx=t->GetTRDsignal()/fMIP;
      Double_t bethe= AliTRDpidESD::Bethe(mom/mass); 
      Double_t sigma=fRes*bethe;
      if (TMath::Abs(dedx-bethe) > fRange*sigma) {
	p[j]=TMath::Exp(-0.5*fRange*fRange)/sigma;
        continue;
      }
      p[j]=TMath::Exp(-0.5*(dedx-bethe)*(dedx-bethe)/(sigma*sigma))/sigma;
    }
    t->SetTRDpid(p);
    //    if(i==50) printf("%f %f %f \n", p[0], p[1], p[2]);
  }
  return 0;
}

*/