G4LELambdaInelastic.cc

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// $Id$
//
// Hadronic Process: Lambda Inelastic Process
// J.L. Chuma, TRIUMF, 18-Feb-1997
// Modified by J.L.Chuma 30-Apr-97: added originalTarget for CalculateMomenta
 
#include <iostream>

#include "G4LELambdaInelastic.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"

G4LELambdaInelastic::G4LELambdaInelastic(const G4String& name)
 :G4InelasticInteraction(name)
{
  SetMinEnergy(0.0);
  SetMaxEnergy(25.*GeV);
  G4cout << "WARNING: model G4LELambdaInelastic is being deprecated and will\n"
         << "disappear in Geant4 version 10.0"  << G4endl;
}


void G4LELambdaInelastic::ModelDescription(std::ostream& outFile) const
{
  outFile << "G4LELambdaInelastic is one of the Low Energy Parameterized\n"
          << "(LEP) models used to implement inelastic Lambda 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 lambdas with initial energies between 0 and 25\n"
          << "GeV.\n";
}


G4HadFinalState*
G4LELambdaInelastic::ApplyYourself(const G4HadProjectile& aTrack,
                                   G4Nucleus& targetNucleus)
{
  const G4HadProjectile *originalIncident = &aTrack;

  // create the target particle

  G4DynamicParticle* originalTarget = targetNucleus.ReturnTargetParticle();
    
  if (verboseLevel > 1) {
    const G4Material *targetMaterial = aTrack.GetMaterial();
    G4cout << "G4LELambdaInelastic::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 G4LELambdaInelastic::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 CASL0 by H. Fesefeldt (13-Sep-1987)
  //
  // Lambda 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[] = { 0.70, 0.35 };
    if( first ) {      // compute normalization constants, this 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=std::max(0,npos-2); nneg<=(npos+1); ++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+2); ++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 *aSigmaPlus = G4SigmaPlus::SigmaPlus();
    G4ParticleDefinition *aSigmaMinus = G4SigmaMinus::SigmaMinus();
    G4ParticleDefinition *aSigmaZero = G4SigmaZero::SigmaZero();
    
    // energetically possible to produce pion(s)  -->  inelastic scattering
    //                                   otherwise quasi-elastic 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=std::max(0,npos-2); 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*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--;
      G4int ncht = std::max( 1, npos-nneg );
      switch( ncht ) {
       case 1:
         currentParticle.SetDefinitionAndUpdateE( aSigmaPlus );
         incidentHasChanged = true;
         break;
       case 2:
         if( G4UniformRand() < 0.5 ) {
           if( G4UniformRand() < 0.5 ) {
             currentParticle.SetDefinitionAndUpdateE( aSigmaZero );
             incidentHasChanged = true;
           }
         } else {
           currentParticle.SetDefinitionAndUpdateE( aSigmaPlus );
           incidentHasChanged = true;
           targetParticle.SetDefinitionAndUpdateE( aNeutron );
           targetHasChanged = true;
         }
         break;
       case 3:
         if( G4UniformRand() < 0.5 ) {
           if( G4UniformRand() < 0.5 ) {
             currentParticle.SetDefinitionAndUpdateE( aSigmaZero );
             incidentHasChanged = true;
           }
           targetParticle.SetDefinitionAndUpdateE( aNeutron );
           targetHasChanged = true;
         } else {
           currentParticle.SetDefinitionAndUpdateE( aSigmaMinus );
           incidentHasChanged = true;
         }
         break;
       default:
         currentParticle.SetDefinitionAndUpdateE( aSigmaMinus );
         incidentHasChanged = true;
         targetParticle.SetDefinitionAndUpdateE( aNeutron );
         targetHasChanged = true;
         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+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*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--;
      G4int ncht = std::max( 1, npos-nneg+3 );
      switch( ncht ) {
       case 1:
         currentParticle.SetDefinitionAndUpdateE( aSigmaPlus );
         incidentHasChanged = true;
         targetParticle.SetDefinitionAndUpdateE( aProton );
         targetHasChanged = true;
         break;
       case 2:
         if( G4UniformRand() < 0.5 ) {
           if( G4UniformRand() < 0.5 ) {
             currentParticle.SetDefinitionAndUpdateE( aSigmaZero );
             incidentHasChanged = true;
           }
           targetParticle.SetDefinitionAndUpdateE( aProton );
           targetHasChanged = true;
         } else {
           currentParticle.SetDefinitionAndUpdateE( aSigmaPlus );
           incidentHasChanged = true;
         }
         break;
       case 3:
         if( G4UniformRand() < 0.5 ) {
           if( G4UniformRand() < 0.5 ) {
             currentParticle.SetDefinitionAndUpdateE( aSigmaZero );
             incidentHasChanged = true;
           }
         } else {
           currentParticle.SetDefinitionAndUpdateE( aSigmaMinus );
           incidentHasChanged = true;
           targetParticle.SetDefinitionAndUpdateE( aProton );
           targetHasChanged = true;
         }
         break;
       default:
         currentParticle.SetDefinitionAndUpdateE( aSigmaMinus );
         incidentHasChanged = true;
         break;
      }
    }

  SetUpPions( npos, nneg, nzero, vec, vecLen );
  return;
}