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// $Id: G4CHIPSElastic.cc,v 1.3 2009/10/08 18:56:57 vnivanch Exp $
// GEANT4 tag $Name: geant4-09-03 $
//
//---------------------------------------------------------------------
//
// Geant4 Class : G4CHIPSElastic
//
// Author : V.Ivanchenko 29 June 2009 
//  
// Modified:
//
//---------------------------------------------------------------------
// CHIPS model of hadron elastic scattering
//

#include "G4CHIPSElastic.hh"
#include "G4VQCrossSection.hh"
#include "G4ParticleDefinition.hh"
#include "G4QElasticCrossSection.hh"

G4VQCrossSection* G4CHIPSElastic::xsManager = 0;

G4CHIPSElastic::G4CHIPSElastic() : G4VHadronElastic("hElasticCHIPS")
{
  if(!xsManager) {xsManager = G4QElasticCrossSection::GetPointer();}
}

G4CHIPSElastic::~G4CHIPSElastic()
{}

G4double 
G4CHIPSElastic::SampleInvariantT(const G4ParticleDefinition* p, 
				 G4double plab, G4int Z, G4int A)
{
  G4int N = A - Z;
  if(Z == 1 && N == 2) N = 1;
  else if(Z == 2 && N == 1) N = 2;
  G4int projPDG = p->GetPDGEncoding();
  G4double cs = xsManager->GetCrossSection(false,plab,Z,N,projPDG);
  G4double t = 0.0;
  if(cs > 0.0) t = xsManager->GetExchangeT(Z,N,projPDG);
  else         t = G4VHadronElastic::SampleInvariantT(p, plab, Z, A);
  return t;
}