STEER/AliTOFPIDResponse.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 //           Implementation of the TOF PID class                   //
  19 //      Origin: Iouri Belikov, CERN, Jouri.Belikov@cern.ch         //
  20 //                                                                 //
  21 //-----------------------------------------------------------------//
  22
  23 #include "TMath.h"
  24 #include "AliLog.h"
  25
  26 #include "AliTOFPIDResponse.h"
  27
  28 ClassImp(AliTOFPIDResponse)
  29
  30 //_________________________________________________________________________
  31 AliTOFPIDResponse::AliTOFPIDResponse():
  32   fSigma(0),
  33   fPmax(0),         // zero at 0.5 GeV/c for pp
  34   fTime0(0)
  35 {
  36 }
  37 //_________________________________________________________________________
  38 AliTOFPIDResponse::AliTOFPIDResponse(Double_t *param):
  39   fSigma(param[0]),
  40   fPmax(0),          // zero at 0.5 GeV/c for pp
  41   fTime0(0)
  42 {
  43   //
  44   //  The main constructor
  45   //
  46   //
  47
  48   //fPmax=TMath::Exp(-0.5*3*3)/fSigma; // ~3 sigma at 0.5 GeV/c for PbPb
  49 }
  50 //_________________________________________________________________________
  51 Double_t
  52 AliTOFPIDResponse::GetMismatchProbability(Double_t p, Double_t mass) const {
  53   //
  54   // Returns the probability of mismatching
  55   // assuming 1/(p*beta)^2 scaling
  56   //
  57   const Double_t km=0.5;                   // "reference" momentum (GeV/c)
  58
  59   Double_t ref2=km*km*km*km/(km*km + mass*mass);// "reference" (p*beta)^2
  60   Double_t p2beta2=p*p*p*p/(p*p + mass*mass);
  61
  62   return fPmax*ref2/p2beta2;
  63 }
  64 //_________________________________________________________________________
  65 Double_t AliTOFPIDResponse::GetExpectedSigma(Float_t mom, Float_t time, Float_t mass) const {
  66   //
  67   // Return the expected sigma of the PID signal for the specified
  68   // particle type.
  69   // If the operation is not possible, return a negative value.
  70   //
  71
  72   Double_t dpp = 0.01;      //mean relative pt resolution;
  73   if (mom>0.5) dpp = 0.01*mom;
  74
  75
  76   Double_t sigma = dpp*time/(1.+ mom*mom/(mass*mass));
  77
  78   return TMath::Sqrt(sigma*sigma + fSigma*fSigma);
  79 }
  80