G4QuasiElasticChannel.cc

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// Author : Gunter Folger March 2007
// Modified by Mikhail Kossov. Apr2009, E/M conservation: ResidualNucleus is added (ResNuc)
// Class Description
// Final state production model for theoretical models of hadron inelastic
// quasi elastic scattering in geant4;
// Class Description - End
//
// Modified:
// 20110805  M. Kelsey -- Follow change to G4V3DNucleus::GetNucleons()
// 20110808  M. Kelsey -- Move #includes from .hh, add many missing

#include "G4QuasiElasticChannel.hh"

#include "G4Fancy3DNucleus.hh"
#include "G4DynamicParticle.hh"
#include "G4HadTmpUtil.hh"        /* lrint */
#include "G4KineticTrack.hh"
#include "G4KineticTrackVector.hh"
#include "G4LorentzVector.hh"
#include "G4Neutron.hh"
#include "G4Nucleon.hh"
#include "G4Nucleus.hh"
#include "G4ParticleDefinition.hh"
#include "G4ParticleTable.hh"
#include "G4QuasiElRatios.hh"
#include "globals.hh"
#include <vector>

//#define debug_scatter


G4QuasiElasticChannel::G4QuasiElasticChannel()
  : theQuasiElastic(G4QuasiElRatios::GetPointer()),
    the3DNucleus(new G4Fancy3DNucleus) {}

G4QuasiElasticChannel::~G4QuasiElasticChannel()
{
  delete the3DNucleus;
}

G4double G4QuasiElasticChannel::GetFraction(G4Nucleus &theNucleus,
    const G4DynamicParticle & thePrimary)
{
    #ifdef debug_scatter   
      G4cout << "G4QuasiElasticChannel:: P=" << thePrimary.GetTotalMomentum()
             << ", pPDG=" << thePrimary.GetDefinition()->GetPDGEncoding()
             << ", Z = "  << theNucleus.GetZ_asInt())
             << ", N = "  << theNucleus.GetN_asInt())
             << ", A = "  << theNucleus.GetA_asInt() << G4endl;
    #endif

  std::pair<G4double,G4double> ratios;
  ratios=theQuasiElastic->GetRatios(thePrimary.GetTotalMomentum(),
                                    thePrimary.GetDefinition()->GetPDGEncoding(),
                                    theNucleus.GetZ_asInt(),
                                    theNucleus.GetN_asInt());
    #ifdef debug_scatter   
      G4cout << "G4QuasiElasticChannel::ratios " << ratios.first << " x " <<ratios.second
             << "  = " << ratios.first*ratios.second << G4endl;
    #endif
        
  return ratios.first*ratios.second;
}

G4KineticTrackVector * G4QuasiElasticChannel::Scatter(G4Nucleus &theNucleus,
                                                      const G4DynamicParticle & thePrimary)
{
  G4int A=theNucleus.GetA_asInt();
  G4int Z=theNucleus.GetZ_asInt();
  //   build Nucleus and choose random nucleon to scatter with
  the3DNucleus->Init(theNucleus.GetA_asInt(),theNucleus.GetZ_asInt());
  const std::vector<G4Nucleon>& nucleons=the3DNucleus->GetNucleons();
  G4double targetNucleusMass=the3DNucleus->GetMass();
  G4LorentzVector targetNucleus4Mom(0.,0.,0.,targetNucleusMass);
  G4int index;
  do {
    index=G4lrint((A-1)*G4UniformRand());
  } while (index < 0 || index >= static_cast<G4int>(nucleons.size()));

  G4ParticleDefinition * pDef= nucleons[index].GetDefinition();

  G4int resA=A - 1;
  G4int resZ=Z - static_cast<int>(pDef->GetPDGCharge());
  G4ParticleDefinition* resDef;
  G4double residualNucleusMass;
  if(resZ)
  {
    resDef=G4ParticleTable::GetParticleTable()->FindIon(resZ,resA,0,resZ);
    residualNucleusMass=resDef->GetPDGMass();
  }
  else {
    resDef=G4Neutron::Neutron();
    residualNucleusMass=resA * G4Neutron::Neutron()->GetPDGMass();
  }
   #ifdef debug_scatter
     G4cout<<"G4QElChan::Scatter: neutron - proton? A ="<<A<<", Z="<<Z<<", projName="
           <<pDef->GetParticleName()<<G4endl;
   #endif

  G4LorentzVector pNucleon=nucleons[index].Get4Momentum();
  G4double residualNucleusEnergy=std::sqrt(sqr(residualNucleusMass) +
                                           pNucleon.vect().mag2());
  pNucleon.setE(targetNucleusMass-residualNucleusEnergy);
  G4LorentzVector residualNucleus4Mom=targetNucleus4Mom-pNucleon;
 
  std::pair<G4LorentzVector,G4LorentzVector> result;
 
  result=theQuasiElastic->Scatter(pDef->GetPDGEncoding(),pNucleon,
                                  thePrimary.GetDefinition()->GetPDGEncoding(),
                                  thePrimary.Get4Momentum());
  G4LorentzVector scatteredHadron4Mom;
  if (result.first.e() > 0.)
    scatteredHadron4Mom=result.second;
  else {  //scatter failed
    //G4cout << "Warning - G4QuasiElasticChannel::Scatter no scattering" << G4endl;
    //return 0;       //no scatter
    scatteredHadron4Mom=thePrimary.Get4Momentum();
    residualNucleus4Mom=G4LorentzVector(0.,0.,0.,targetNucleusMass);
    resDef=G4ParticleTable::GetParticleTable()->FindIon(Z,A,0,Z);
  }

#ifdef debug_scatter
  G4LorentzVector EpConservation=pNucleon+thePrimary.Get4Momentum() 
                                 - result.first - result.second;
  if (   (EpConservation.vect().mag2() > .01*MeV*MeV )
      || (std::abs(EpConservation.e()) > 0.1 * MeV ) ) 
  {
    G4cout << "Warning - G4QuasiElasticChannel::Scatter E-p non conservation : "
           << EpConservation << G4endl;
  }    
#endif

  G4KineticTrackVector * ktv = new G4KineticTrackVector();
  G4KineticTrack * sPrim=new G4KineticTrack(thePrimary.GetDefinition(),
                                            0.,G4ThreeVector(0), scatteredHadron4Mom);
  ktv->push_back(sPrim);
  if (result.first.e() > 0.)
  {
    G4KineticTrack * sNuc=new G4KineticTrack(pDef, 0.,G4ThreeVector(0), result.first);
    ktv->push_back(sNuc);
  }
  if(resZ || resA==1) // For the only neutron or for tnuclei with Z>0 
  {
    G4KineticTrack * rNuc=new G4KineticTrack(resDef,
                           0.,G4ThreeVector(0), residualNucleus4Mom);
    ktv->push_back(rNuc);
  }
  else // The residual nucleus consists of only neutrons 
  {
    residualNucleus4Mom/=resA;     // Split 4-mom of A*n system equally
    for(G4int in=0; in<resA; in++) // Loop over neutrons in A*n system.
    {
      G4KineticTrack* rNuc=new G4KineticTrack(resDef,
                           0.,G4ThreeVector(0), residualNucleus4Mom);
      ktv->push_back(rNuc);
    }
  }
#ifdef debug_scatter
  G4cout<<"G4QElC::Scat: Nucleon: "<<result.first <<" mass "<<result.first.mag() << G4endl;
  G4cout<<"G4QElC::Scat: Project: "<<result.second<<" mass "<<result.second.mag()<< G4endl;
#endif
  return ktv;
}

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