/**************************************************************************
 * Copyright(c) 1998-1999, 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.                  *
 **************************************************************************/

//-----------------------------------------------------------------//
//                                                                 //
//           Implementation of the TOF PID class                   //
//      Origin: Iouri Belikov, CERN, Jouri.Belikov@cern.ch         //
//                                                                 //
//-----------------------------------------------------------------//

#include "TMath.h"
#include "AliLog.h"

#include "AliTOFPIDResponse.h"

ClassImp(AliTOFPIDResponse)

//_________________________________________________________________________
AliTOFPIDResponse::AliTOFPIDResponse(): 
  fSigma(0),
  fPmax(0),         // zero at 0.5 GeV/c for pp
  fTime0(0)
{
}
//_________________________________________________________________________
AliTOFPIDResponse::AliTOFPIDResponse(Double_t *param):
  fSigma(param[0]),
  fPmax(0),          // zero at 0.5 GeV/c for pp
  fTime0(0)
{
  //
  //  The main constructor
  //
  //

  //fPmax=TMath::Exp(-0.5*3*3)/fSigma; // ~3 sigma at 0.5 GeV/c for PbPb 
}
//_________________________________________________________________________
Double_t 
AliTOFPIDResponse::GetMismatchProbability(Double_t p, Double_t mass) const {
  //
  // Returns the probability of mismatching 
  // assuming 1/(p*beta)^2 scaling
  //
  const Double_t km=0.5;                   // "reference" momentum (GeV/c)

  Double_t ref2=km*km*km*km/(km*km + mass*mass);// "reference" (p*beta)^2
  Double_t p2beta2=p*p*p*p/(p*p + mass*mass);

  return fPmax*ref2/p2beta2;
}
//_________________________________________________________________________
Double_t AliTOFPIDResponse::GetExpectedSigma(Float_t mom, Float_t time, Float_t mass) const {
  //
  // Return the expected sigma of the PID signal for the specified
  // particle type.
  // If the operation is not possible, return a negative value.
  //

  Double_t dpp = 0.01;      //mean relative pt resolution;
  if (mom>0.5) dpp = 0.01*mom;

 
  Double_t sigma = dpp*time/(1.+ mom*mom/(mass*mass));

  return TMath::Sqrt(sigma*sigma + fSigma*fSigma);
}