G4LESigmaPlusInelastic.cc

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// $Id$
//
// Hadronic Process: SigmaPlus Inelastic Process
// J.L. Chuma, TRIUMF, 19-Feb-1997
// Modified by J.L.Chuma 30-Apr-97: added originalTarget for CalculateMomenta
 
#include "G4LESigmaPlusInelastic.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"
 
void G4LESigmaPlusInelastic::ModelDescription(std::ostream& outFile) const
{
  outFile << "G4LESigmaPlusInelastic is one of the Low Energy Parameterized\n"
          << "(LEP) models used to implement inelastic Sigma+ scattering\n"
          << "from nuclei.  It is a re-engineered version of the GHEISHA\n"
          << "code of H. Fesefeldt.  It divides the initial collision\n"
          << "products into backward- and forward-going clusters which are\n"
          << "then decayed into final state hadrons.  The model does not\n"
          << "conserve energy on an event-by-event basis.  It may be\n"
          << "applied to Sigma+ with initial energies between 0 and 25\n"
          << "GeV.\n";
}

G4HadFinalState*
G4LESigmaPlusInelastic::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 << "G4LESigmaPlusInelastic::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);

  if (isotopeProduction) DoIsotopeCounting(originalIncident, targetNucleus);

  delete originalTarget;
  return &theParticleChange;
}

 
void G4LESigmaPlusInelastic::Cascade(
   G4FastVector<G4ReactionProduct,GHADLISTSIZE> &vec,
   G4int& vecLen,
   const G4HadProjectile *originalIncident,
   G4ReactionProduct &currentParticle,
   G4ReactionProduct &targetParticle,
   G4bool &incidentHasChanged,
   G4bool &targetHasChanged,
   G4bool &quasiElastic )
{
  // derived from original FORTRAN code CASSP by H. Fesefeldt (30-Nov-1987)
  //
  // SigmaPlus 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 G4bool first = true;
  const G4int numMul = 1200;
  const G4int numSec = 60;
  static G4double protmul[numMul], protnorm[numSec]; // proton constants
  static G4double neutmul[numMul], neutnorm[numSec]; // neutron constants

  // npos = number of pi+, nneg = number of pi-, nzero = number of pi0
  G4int counter, nt=0, npos=0, nneg=0, nzero=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 (npos = 0; npos < (numSec/3); ++npos) {
      for (nneg = npos; nneg <= (npos+2); ++nneg) {
        for (nzero = 0; nzero < numSec/3; ++nzero) {
          if (++counter < numMul) {
            nt = npos+nneg+nzero;
            if (nt > 0 && nt <= numSec) {
              protmul[counter] = Pmltpc(npos,nneg,nzero,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( npos=0; npos<numSec/3; ++npos )
      {
        for( nneg=std::max(0,npos-1); nneg<=(npos+1); ++nneg )
        {
          for( nzero=0; nzero<numSec/3; ++nzero )
          {
            if( ++counter < numMul )
            {
              nt = npos+nneg+nzero;
              if( nt>0 && nt<=numSec )
              {
                neutmul[counter] = Pmltpc(npos,nneg,nzero,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 *aLambda = G4Lambda::Lambda();
  G4ParticleDefinition *aSigmaZero = G4SigmaZero::SigmaZero();

  // 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( npos=0; npos<numSec/3 && ran>=excs; ++npos )
      {
        for( nneg=npos; nneg<=(npos+2) && ran>=excs; ++nneg )
        {
          for( nzero=0; nzero<numSec/3 && ran>=excs; ++nzero )
          {
            if( ++counter < numMul )
            {
              nt = npos+nneg+nzero;
              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;
      }
      npos--; nneg--; nzero--;
      switch( std::min( 3, std::max( 1, npos-nneg+3 ) ) )
      {
       case 1:
         if( G4UniformRand() < 0.5 )
           currentParticle.SetDefinitionAndUpdateE( aLambda );
         else
           currentParticle.SetDefinitionAndUpdateE( aSigmaZero );
         incidentHasChanged = true;
         targetParticle.SetDefinitionAndUpdateE( aNeutron );
         targetHasChanged = true;
         break;
       case 2:
         if( G4UniformRand() < 0.5 )
         {
           targetParticle.SetDefinitionAndUpdateE( aNeutron );
           targetHasChanged = true;
         }
         else
         {
           if( G4UniformRand() < 0.5 )
             currentParticle.SetDefinitionAndUpdateE( aLambda );
           else
             currentParticle.SetDefinitionAndUpdateE( aSigmaZero );
           incidentHasChanged = true;
         }             
         break;
       case 3:
         break;
      }
    }
    else  // target must be a neutron
    {
      counter = -1;
      for( npos=0; npos<numSec/3 && ran>=excs; ++npos )
      {
        for( nneg=std::max(0,npos-1); nneg<=(npos+1) && ran>=excs; ++nneg )
        {
          for( nzero=0; nzero<numSec/3 && ran>=excs; ++nzero )
          {
            if( ++counter < numMul )
            {
              nt = npos+nneg+nzero;
              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;
      }
      npos--; nneg--; nzero--;
      switch( std::min( 3, std::max( 1, npos-nneg+2 ) ) )
      {
       case 1:
         targetParticle.SetDefinitionAndUpdateE( aProton );
         targetHasChanged = true;
         break;
       case 2:
         if( G4UniformRand() < 0.5 )
         {
           if( G4UniformRand() < 0.5 )
           {
             currentParticle.SetDefinitionAndUpdateE( aLambda );
             incidentHasChanged = true;
             targetParticle.SetDefinitionAndUpdateE( aProton );
             targetHasChanged = true;
           }
           else
           {
             targetParticle.SetDefinitionAndUpdateE( aNeutron );
             targetHasChanged = true;
           }
         }
         else
         {
           if( G4UniformRand() < 0.5 )
           {
             currentParticle.SetDefinitionAndUpdateE( aSigmaZero );
             incidentHasChanged = true;
             targetParticle.SetDefinitionAndUpdateE( aProton );
             targetHasChanged = true;
           }
         }
         break;
       case 3:
         if( G4UniformRand() < 0.5 )
           currentParticle.SetDefinitionAndUpdateE( aLambda );
         else
           currentParticle.SetDefinitionAndUpdateE( aSigmaZero );
         incidentHasChanged = true;
         break;
      }
    }
  SetUpPions(npos, nneg, nzero, vec, vecLen);
  return;
}

 /* end of file */
 

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