STEER/AliHMPIDPIDResponse.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 "AliHMPIDRecon.h"     //class header
  27 #include <AliESDtrack.h>       //FindPid()
  28 #include <TRandom.h>           //Resolution()
  29
  30 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  31 AliHMPIDPid::AliHMPIDPid():TNamed("HMPIDrec","HMPIDPid")
  32 {
  33 //..
  34 //init of data members
  35 //..
  36 }
  37 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  38 Double_t AliHMPIDPIDResponse::CosTheta(Float_t mom, Int_t species) {
  39   Double_t mass = AliPID::ParticleMass(species);
  40   TMath::Sqrt(mass*mass+pmod*pmod)/(AliHMPIDParam::Instance()->MeanIdxRad()*pmod);                   //  evaluate the theor. Theta Cherenkov
  41 }
  42 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  43 Double_t AliHMPIDPIDResponse::Resolution(Double_t thetaCerTh, AliESDtrack *pTrk)
  44 {
  45   AliHMPIDParam *pParam = AliHMPIDParam::Instance();
  46
  47   AliHMPIDRecon rec;
  48   Float_t xRa,yRa,thRa,phRa;
  49   pTrk->GetHMPIDtrk(xRa,yRa,thRa,phRa);
  50   rec.SetTrack(xRa,yRa,thRa,phRa);
  51   Double_t thetaMax = TMath::ACos(1./pParam->MeanIdxRad());
  52   Int_t nPhots = (Int_t)(21.*TMath::Sin(thetaCerTh)*TMath::Sin(thetaCerTh)/(TMath::Sin(thetaMax)*TMath::Sin(thetaMax))+0.01);
  53
  54   Double_t sigmatot = 0;
  55   Int_t nTrks = 20;
  56   for(Int_t iTrk=0;iTrk<nTrks;iTrk++) {
  57     Double_t invSigma = 0;
  58     Int_t nPhotsAcc = 0;
  59     for(Int_t j=0;j<nPhots;j++){
  60       Double_t phi = gRandom->Rndm()*TMath::TwoPi();
  61       TVector2 pos; pos=rec.TracePhot(thetaCerTh,phi);
  62       if(!pParam->IsInside(pos.X(),pos.Y())) continue;
  63       if(pParam->IsInDead(pos.X(),pos.Y())) continue;
  64       Double_t sigma2 = pParam->Sigma2(thRa,phRa,thetaCerTh,phi);//photon candidate sigma^2
  65       if(sigma2!=0) {
  66         invSigma += 1./sigma2;
  67         nPhotsAcc++;
  68       }
  69     }
  70     if(invSigma!=0) sigmatot += 1./TMath::Sqrt(invSigma);
  71   }
  72   return sigmatot/nTrks;
  73 }