G4RPGXiZeroInelastic.cc

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// $Id$
//
 
#include "G4RPGXiZeroInelastic.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"
 
G4HadFinalState*
G4RPGXiZeroInelastic::ApplyYourself(const G4HadProjectile& aTrack,
                                    G4Nucleus& targetNucleus)
{    
  const G4HadProjectile *originalIncident = &aTrack;
  if (originalIncident->GetKineticEnergy() <= 0.1*MeV) {
    theParticleChange.SetStatusChange(isAlive);
    theParticleChange.SetEnergyChange(aTrack.GetKineticEnergy());
    theParticleChange.SetMomentumChange(aTrack.Get4Momentum().vect().unit()); 
    return &theParticleChange;      
  }

  // create the target particle
  G4DynamicParticle* originalTarget = targetNucleus.ReturnTargetParticle();
    
  if (verboseLevel > 1) {
    const G4Material *targetMaterial = aTrack.GetMaterial();
    G4cout << "G4RPGXiZeroInelastic::ApplyYourself called" << G4endl;
    G4cout << "kinetic energy = " << originalIncident->GetKineticEnergy()/MeV << "MeV, ";
    G4cout << "target material = " << targetMaterial->GetName() << ", ";
    G4cout << "target particle = " << originalTarget->GetDefinition()->GetParticleName()
           << G4endl;
  }

  // Fermi motion and evaporation
  // As of Geant3, the Fermi energy calculation had not been Done
  G4double ek = originalIncident->GetKineticEnergy()/MeV;
  G4double amas = originalIncident->GetDefinition()->GetPDGMass()/MeV;
  G4ReactionProduct modifiedOriginal;
  modifiedOriginal = *originalIncident;
    
    G4double tkin = targetNucleus.Cinema( ek );
    ek += tkin;
    modifiedOriginal.SetKineticEnergy( ek*MeV );
    G4double et = ek + amas;
    G4double p = std::sqrt( std::abs((et-amas)*(et+amas)) );
    G4double pp = modifiedOriginal.GetMomentum().mag()/MeV;
    if( pp > 0.0 )
    {
      G4ThreeVector momentum = modifiedOriginal.GetMomentum();
      modifiedOriginal.SetMomentum( momentum * (p/pp) );
    }
    //
    // calculate black track energies
    //
    tkin = targetNucleus.EvaporationEffects( ek );
    ek -= tkin;
    modifiedOriginal.SetKineticEnergy( ek*MeV );
    et = ek + amas;
    p = std::sqrt( std::abs((et-amas)*(et+amas)) );
    pp = modifiedOriginal.GetMomentum().mag()/MeV;
    if( pp > 0.0 )
    {
      G4ThreeVector momentum = modifiedOriginal.GetMomentum();
      modifiedOriginal.SetMomentum( momentum * (p/pp) );
    }
  G4ReactionProduct currentParticle = modifiedOriginal;
  G4ReactionProduct targetParticle;
  targetParticle = *originalTarget;
  currentParticle.SetSide( 1 ); // incident always goes in forward hemisphere
  targetParticle.SetSide( -1 );  // target always goes in backward hemisphere
  G4bool incidentHasChanged = false;
  G4bool targetHasChanged = false;
  G4bool quasiElastic = false;
  G4FastVector<G4ReactionProduct,GHADLISTSIZE> vec;  // vec will contain the secondary particles
  G4int vecLen = 0;
  vec.Initialize( 0 );
    
  const G4double cutOff = 0.1;
  if (currentParticle.GetKineticEnergy()/MeV > cutOff)
    Cascade(vec, vecLen, originalIncident, currentParticle, targetParticle,
            incidentHasChanged, targetHasChanged, quasiElastic);
    
  CalculateMomenta(vec, vecLen, originalIncident, originalTarget,
                   modifiedOriginal, targetNucleus, currentParticle,
                   targetParticle, incidentHasChanged, targetHasChanged,
                   quasiElastic);
    
  SetUpChange(vec, vecLen, currentParticle, targetParticle, incidentHasChanged);
    
  delete originalTarget;
  return &theParticleChange;
}


void
G4RPGXiZeroInelastic::Cascade(G4FastVector<G4ReactionProduct,GHADLISTSIZE> &vec,
                              G4int& vecLen,
                              const G4HadProjectile* originalIncident,
                              G4ReactionProduct& currentParticle,
                              G4ReactionProduct& targetParticle,
                              G4bool& incidentHasChanged,
                              G4bool& targetHasChanged,
                              G4bool& quasiElastic)
{
  // Derived from H. Fesefeldt's original FORTRAN code CASX0
  //
  // XiZero undergoes interaction with nucleon within a nucleus.  Check if it is
  // energetically possible to produce pions/kaons.  In not, assume nuclear excitation
  // occurs and input particle is degraded in energy. No other particles are produced.
  // If reaction is possible, find the correct number of pions/protons/neutrons
  // produced using an interpolation to multiplicity data.  Replace some pions or
  // protons/neutrons by kaons or strange baryons according to the average
  // multiplicity per inelastic reaction.

  const G4double mOriginal = originalIncident->GetDefinition()->GetPDGMass()/MeV;
  const G4double etOriginal = originalIncident->GetTotalEnergy()/MeV;
  const G4double targetMass = targetParticle.GetMass()/MeV;
  G4double centerofmassEnergy = std::sqrt(mOriginal*mOriginal +
                                          targetMass*targetMass +
                                          2.0*targetMass*etOriginal);
  G4double availableEnergy = centerofmassEnergy-(targetMass+mOriginal);
  if (availableEnergy <= G4PionPlus::PionPlus()->GetPDGMass()/MeV) {
    quasiElastic = true;
    return;
  }
  static G4ThreadLocal G4bool first = true;
  const G4int numMul = 1200;
  const G4int numSec = 60;
  static G4ThreadLocal G4double protmul[numMul], protnorm[numSec]; // proton constants
  static G4ThreadLocal G4double neutmul[numMul], neutnorm[numSec]; // neutron constants

  // np = number of pi+, nneg = number of pi-, nz = number of pi0
  G4int counter, nt=0, np=0, nneg=0, nz=0;
  G4double test;
  const G4double c = 1.25;    
  const G4double b[] = { 0.7, 0.7 };
  if (first) {  // Computation of normalization constants will only be done once
    first = false;
    G4int i;
    for (i = 0; i < numMul; ++i) protmul[i] = 0.0;
    for (i = 0; i < numSec; ++i) protnorm[i] = 0.0;
    counter = -1;
    for( np=0; np<(numSec/3); ++np )
      {
        for( nneg=std::max(0,np-2); nneg<=(np+1); ++nneg )
        {
          for( nz=0; nz<numSec/3; ++nz )
          {
            if( ++counter < numMul )
            {
              nt = np+nneg+nz;
              if( nt>0 && nt<=numSec )
              {
                protmul[counter] = Pmltpc(np,nneg,nz,nt,b[0],c);
                protnorm[nt-1] += protmul[counter];
              }
            }
          }
        }
      }
      for( i=0; i<numMul; ++i )neutmul[i] = 0.0;
      for( i=0; i<numSec; ++i )neutnorm[i] = 0.0;
      counter = -1;
      for( np=0; np<numSec/3; ++np )
      {
        for( nneg=std::max(0,np-1); nneg<=(np+2); ++nneg )
        {
          for( nz=0; nz<numSec/3; ++nz )
          {
            if( ++counter < numMul )
            {
              nt = np+nneg+nz;
              if( nt>0 && nt<=numSec )
              {
                neutmul[counter] = Pmltpc(np,nneg,nz,nt,b[1],c);
                neutnorm[nt-1] += neutmul[counter];
              }
            }
          }
        }
      }
      for( i=0; i<numSec; ++i )
      {
        if( protnorm[i] > 0.0 )protnorm[i] = 1.0/protnorm[i];
        if( neutnorm[i] > 0.0 )neutnorm[i] = 1.0/neutnorm[i];
      }
    }   // end of initialization
    
    const G4double expxu = 82.;           // upper bound for arg. of exp
    const G4double expxl = -expxu;        // lower bound for arg. of exp
    G4ParticleDefinition *aNeutron = G4Neutron::Neutron();
    G4ParticleDefinition *aProton = G4Proton::Proton();
    G4ParticleDefinition *aKaonMinus = G4KaonMinus::KaonMinus();
    G4ParticleDefinition *aSigmaPlus = G4SigmaPlus::SigmaPlus();
    G4ParticleDefinition *aXiMinus = G4XiMinus::XiMinus();
    //
    // energetically possible to produce pion(s)  -->  inelastic scattering
    //
    G4double n, anpn;
    GetNormalizationConstant( availableEnergy, n, anpn );
    G4double ran = G4UniformRand();
    G4double dum, excs = 0.0;
    if( targetParticle.GetDefinition() == aProton )
    {
      counter = -1;
      for( np=0; np<numSec/3 && ran>=excs; ++np )
      {
        for( nneg=std::max(0,np-2); nneg<=(np+1) && ran>=excs; ++nneg )
        {
          for( nz=0; nz<numSec/3 && ran>=excs; ++nz )
          {
            if( ++counter < numMul )
            {
              nt = np+nneg+nz;
              if( nt>0 && nt<=numSec )
              {
                test = std::exp( std::min( expxu, std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
                dum = (pi/anpn)*nt*protmul[counter]*protnorm[nt-1]/(2.0*n*n);
                if( std::fabs(dum) < 1.0 )
                {
                  if( test >= 1.0e-10 )excs += dum*test;
                }
                else
                  excs += dum*test;
              }
            }
          }
        }
      }
      if( ran >= excs )  // 3 previous loops continued to the end
      {
        quasiElastic = true;
        return;
      }
      np--; nneg--; nz--;
      //
      // number of secondary mesons determined by kno distribution
      // check for total charge of final state mesons to determine
      // the kind of baryons to be produced, taking into account
      // charge and strangeness conservation
      //
      if( np < nneg+1 )
      {
        if( np != nneg )   // charge mismatch
        {
          currentParticle.SetDefinitionAndUpdateE( aSigmaPlus );
          incidentHasChanged = true;
          //
          // correct the strangeness by replacing a pi- by a kaon-
          //
          vec.Initialize( 1 );
          G4ReactionProduct *p = new G4ReactionProduct;
          p->SetDefinition( aKaonMinus );
          (G4UniformRand() < 0.5) ? p->SetSide( -1 ) : p->SetSide( 1 );
          vec.SetElement( vecLen++, p );
          --nneg;
        }
      }
      else if( np == nneg+1 )
      {
        if( G4UniformRand() < 0.5 )
        {
          targetParticle.SetDefinitionAndUpdateE( aNeutron );
          targetHasChanged = true;
        }
        else
        {
          currentParticle.SetDefinitionAndUpdateE( aXiMinus );
          incidentHasChanged = true;
        }
      }
      else
      {
        currentParticle.SetDefinitionAndUpdateE( aXiMinus );
        incidentHasChanged = true;
        targetParticle.SetDefinitionAndUpdateE( aNeutron );
        targetHasChanged = true;
      }
    }
    else  // target must be a neutron
    {
      counter = -1;
      for( np=0; np<numSec/3 && ran>=excs; ++np )
      {
        for( nneg=std::max(0,np-1); nneg<=(np+2) && ran>=excs; ++nneg )
        {
          for( nz=0; nz<numSec/3 && ran>=excs; ++nz )
          {
            if( ++counter < numMul )
            {
              nt = np+nneg+nz;
              if( nt>0 && nt<=numSec )
              {
                test = std::exp( std::min( expxu, std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
                dum = (pi/anpn)*nt*neutmul[counter]*neutnorm[nt-1]/(2.0*n*n);
                if( std::fabs(dum) < 1.0 )
                {
                  if( test >= 1.0e-10 )excs += dum*test;
                }
                else
                  excs += dum*test;
              }
            }
          }
        }
      }
      if( ran >= excs )  // 3 previous loops continued to the end
      {
        quasiElastic = true;
        return;
      }
      np--; nneg--; nz--;
      if( np < nneg )
      {
        if( np+1 == nneg )
        {
          targetParticle.SetDefinitionAndUpdateE( aProton );
          targetHasChanged = true;
        }
        else   // charge mismatch
        {
          currentParticle.SetDefinitionAndUpdateE( aSigmaPlus );
          incidentHasChanged = true;
          targetParticle.SetDefinitionAndUpdateE( aProton );
          targetHasChanged = true;
          //
          // correct the strangeness by replacing a pi- by a kaon-
          //
          vec.Initialize( 1 );
          G4ReactionProduct *p = new G4ReactionProduct;
          p->SetDefinition( aKaonMinus );
          (G4UniformRand() < 0.5) ? p->SetSide( -1 ) : p->SetSide( 1 );
          vec.SetElement( vecLen++, p );
          --nneg;
        }
      }
      else if( np == nneg )
      {
        if( G4UniformRand() >= 0.5 )
        {
          currentParticle.SetDefinitionAndUpdateE( aXiMinus );
          incidentHasChanged = true;
          targetParticle.SetDefinitionAndUpdateE( aProton );
          targetHasChanged = true;
        }
      }
      else
      {
        currentParticle.SetDefinitionAndUpdateE( aXiMinus );
        incidentHasChanged = true;
      }        
  }

  SetUpPions(np, nneg, nz, vec, vecLen);
  return;
}

 /* end of file */