G4RPGKPlusInelastic.cc

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// $Id$
//
 
#include "G4RPGKPlusInelastic.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"
 
G4HadFinalState*
G4RPGKPlusInelastic::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();
  G4ReactionProduct targetParticle( originalTarget->GetDefinition() );
    
  if( verboseLevel > 1 )
  {
    const G4Material *targetMaterial = aTrack.GetMaterial();
    G4cout << "G4RPGKPlusInelastic::ApplyYourself called" << G4endl;
    G4cout << "kinetic energy = " << originalIncident->GetKineticEnergy() << "MeV, ";
    G4cout << "target material = " << targetMaterial->GetName() << ", ";
    G4cout << "target particle = " << originalTarget->GetDefinition()->GetParticleName()
           << G4endl;
  }    
  G4ReactionProduct currentParticle( const_cast<G4ParticleDefinition *>(originalIncident->GetDefinition()));
  currentParticle.SetMomentum( originalIncident->Get4Momentum().vect() );
  currentParticle.SetKineticEnergy( originalIncident->GetKineticEnergy() );
    
  // Fermi motion and evaporation
  // As of Geant3, the Fermi energy calculation had not been Done
    
  G4double ek = originalIncident->GetKineticEnergy();
  G4double amas = originalIncident->GetDefinition()->GetPDGMass();
    
  G4double tkin = targetNucleus.Cinema( ek );
  ek += tkin;
  currentParticle.SetKineticEnergy( ek );
  G4double et = ek + amas;
  G4double p = std::sqrt( std::abs((et-amas)*(et+amas)) );
  G4double pp = currentParticle.GetMomentum().mag();
  if( pp > 0.0 )
  {
    G4ThreeVector momentum = currentParticle.GetMomentum();
    currentParticle.SetMomentum( momentum * (p/pp) );
  }
    
  // calculate black track energies
    
  tkin = targetNucleus.EvaporationEffects( ek );
  ek -= tkin;
  currentParticle.SetKineticEnergy( ek );
  et = ek + amas;
  p = std::sqrt( std::abs((et-amas)*(et+amas)) );
  pp = currentParticle.GetMomentum().mag();
  if( pp > 0.0 )
  {
    G4ThreeVector momentum = currentParticle.GetMomentum();
    currentParticle.SetMomentum( momentum * (p/pp) );
  }
    
  G4ReactionProduct modifiedOriginal = currentParticle;
    
  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*MeV;
  if( currentParticle.GetKineticEnergy() > 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 G4RPGKPlusInelastic::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 CASKP
  //
  // K+ 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();
  const G4double etOriginal = originalIncident->GetTotalEnergy();
  const G4double targetMass = targetParticle.GetMass();
  G4double centerofmassEnergy = std::sqrt( mOriginal*mOriginal +
                                        targetMass*targetMass +
                                        2.0*targetMass*etOriginal );
  G4double availableEnergy = centerofmassEnergy-(targetMass+mOriginal);
  if( availableEnergy < G4PionPlus::PionPlus()->GetPDGMass() )
  {
    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

  // np = number of pi+, nneg = number of pi-, nz = number of pi0

  G4int nt=0, np=0, nneg=0, nz=0;
  const G4double c = 1.25;    
  const G4double b[] = { 0.70, 0.70 };
  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;
      G4int counter = -1;
      for( np=0; np<(numSec/3); ++np )
      {
        for( nneg=std::max(0,np-2); nneg<=np; ++nneg )
        {
          for( nz=0; nz<numSec/3; ++nz )
          {
            if( ++counter < numMul )
            {
              nt = np+nneg+nz;
              if( nt > 0 )
              {
                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+1); ++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 *aKaonZS = G4KaonZeroShort::KaonZeroShort();
  G4ParticleDefinition *aKaonZL = G4KaonZeroLong::KaonZeroLong();
  G4ParticleDefinition *aNeutron = G4Neutron::Neutron();
  G4ParticleDefinition *aProton = G4Proton::Proton();
  G4int ieab = static_cast<G4int>(availableEnergy*5.0/GeV);
  const G4double supp[] = {0.,0.4,0.55,0.65,0.75,0.82,0.86,0.90,0.94,0.98};
  G4double test, w0, wp, wt, wm;
  if( (availableEnergy < 2.0*GeV) && (G4UniformRand() >= supp[ieab]) )
  {
    // suppress high multiplicity events at low momentum
    // only one pion will be produced
      
    nneg = np = nz = 0;
    if( targetParticle.GetDefinition() == aProton )
    {
      test = std::exp( std::min( expxu, std::max( expxl, -sqr(1.0+b[0])/(2.0*c*c) ) ) );
      w0 = test;
      wp = test*2.0;        
      if( G4UniformRand() < w0/(w0+wp) )
        nz = 1;
      else
        np = 1;
    }
    else  // target is a neutron
    {
      test = std::exp( std::min( expxu, std::max( expxl, -sqr(1.0+b[1])/(2.0*c*c) ) ) );
      w0 = test;
      wp = test;
      test = std::exp( std::min( expxu, std::max( expxl, -sqr(-1.0+b[1])/(2.0*c*c) ) ) );
      wm = test;
      wt = w0+wp+wm;
      wp += w0;
      G4double ran = G4UniformRand();
      if( ran < w0/wt )
        nz = 1;
      else if( ran < wp/wt )
        np = 1;
      else
        nneg = 1;
    }
  }
  else
  {
      G4double n, anpn;
      GetNormalizationConstant( availableEnergy, n, anpn );
      G4double ran = G4UniformRand();
      G4double dum, excs = 0.0;
      if( targetParticle.GetDefinition() == aProton )
      {
        G4int counter = -1;
        for( np=0; (np<numSec/3) && (ran>=excs); ++np )
        {
          for( nneg=std::max(0,np-2); (nneg<=np) && (ran>=excs); ++nneg )
          {
            for( nz=0; (nz<numSec/3) && (ran>=excs); ++nz )
            {
              if( ++counter < numMul )
              {
                nt = np+nneg+nz;
                if( nt > 0 )
                {
                  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 )return;  // 3 previous loops continued to the end
        np--; nneg--; nz--;
      }
      else  // target must be a neutron
      {
        G4int counter = -1;
        for( np=0; (np<numSec/3) && (ran>=excs); ++np )
        {
          for( nneg=std::max(0,np-1); (nneg<=(np+1)) && (ran>=excs); ++nneg )
          {
            for( nz=0; (nz<numSec/3) && (ran>=excs); ++nz )
            {
              if( ++counter < numMul )
              {
                nt = np+nneg+nz;
                if( (nt>=1) && (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 )return;  // 3 previous loops continued to the end
        np--; nneg--; nz--;
      }
  }

  if( targetParticle.GetDefinition() == aProton )
  {
    switch( np-nneg )
    {
     case 1:
       if( G4UniformRand() < 0.5 )
       {
         if( G4UniformRand() < 0.5 )
           currentParticle.SetDefinitionAndUpdateE( aKaonZS );
         else
           currentParticle.SetDefinitionAndUpdateE( aKaonZL );
         incidentHasChanged = true;
       }
       else
       {
         targetParticle.SetDefinitionAndUpdateE( aNeutron );
         targetHasChanged = true;
       }
       break;
     case 2:
       if( G4UniformRand() < 0.5 )
         currentParticle.SetDefinitionAndUpdateE( aKaonZS );
       else
         currentParticle.SetDefinitionAndUpdateE( aKaonZL );
       incidentHasChanged = true;
       targetParticle.SetDefinitionAndUpdateE( aNeutron );
       incidentHasChanged = true;
       targetHasChanged = true;
       break;
     default:
       break;
    }
  }
  else   // target is a neutron
  {
    switch( np-nneg )
    {
     case 0:
       if( G4UniformRand() < 0.25 )
       {
         if( G4UniformRand() < 0.5 )
           currentParticle.SetDefinitionAndUpdateE( aKaonZS );
         else
           currentParticle.SetDefinitionAndUpdateE( aKaonZL );
         targetParticle.SetDefinitionAndUpdateE( aProton );
         incidentHasChanged = true;
         targetHasChanged = true;
       }
       break;
     case 1:
       if( G4UniformRand() < 0.5 )
         currentParticle.SetDefinitionAndUpdateE( aKaonZS );
       else
         currentParticle.SetDefinitionAndUpdateE( aKaonZL );
       incidentHasChanged = true;
       break;
     default: // assumes nneg = np+1 so charge is conserved
       targetParticle.SetDefinitionAndUpdateE( aProton );
       targetHasChanged = true;
       break;
    }
  }

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

 /* end of file */