G4LEAntiNeutronInelastic.cc

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// $Id$
//
// Hadronic Process: AntiNeutron Inelastic Process
// J.L. Chuma, TRIUMF, 18-Feb-1997
// J.P.Wellisch: 23-Apr-97: Added theNucleus.SetParameters call
// J.P. Wellisch: 23-Apr-97: nm = np+1; in line 392
// Modified by J.L.Chuma 30-Apr-97: added originalTarget for CalculateMomenta
//
 
#include <iostream>
 
#include "G4LEAntiNeutronInelastic.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"
 
G4LEAntiNeutronInelastic::G4LEAntiNeutronInelastic(const G4String& name)
 :G4InelasticInteraction(name)
{
  SetMinEnergy(0.0);
  SetMaxEnergy(25.*GeV);
  G4cout << "WARNING: model G4LEAntiNeutronInelastic is being deprecated and will\n"
         << "disappear in Geant4 version 10.0"  << G4endl;
}
 
 
void G4LEAntiNeutronInelastic::ModelDescription(std::ostream& outFile) const
{
  outFile << "G4LEAntiNeutronInelastic is one of the Low Energy\n"
          << "Parameterized (LEP) models used to implement inelastic\n"
          << "anti-neutron scattering from nuclei.  It is a re-engineered\n"
          << "version of the GHEISHA code of H. Fesefeldt.  It divides the\n"
          << "initial collision products into backward- and forward-going\n"
          << "clusters which are then decayed into final state hadrons.\n"
          << "The model does not conserve energy on an event-by-event\n"
          << "basis.  It may be applied to anti-neutrons with initial\n"
          << "energies between 0 and 25 GeV.\n";
}
 
 
G4HadFinalState*
G4LEAntiNeutronInelastic::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 << "G4LEAntiNeutronInelastic::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*MeV;
  const G4double anni = std::min(1.3*currentParticle.GetTotalMomentum()/GeV, 0.4);
    
  if ((currentParticle.GetKineticEnergy()/MeV > cutOff) ||
      (G4UniformRand() > anni) )
    Cascade(vec, vecLen, originalIncident, currentParticle, targetParticle,
            incidentHasChanged, targetHasChanged, quasiElastic);
  else
    quasiElastic = true;
    
  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 G4LEAntiNeutronInelastic::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 CASNB by H. Fesefeldt (13-Sep-1987)
  //
  // AntiNeutron 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 pOriginal = originalIncident->GetTotalMomentum()/MeV;
  const G4double targetMass = targetParticle.GetMass()/MeV;
  G4double centerofmassEnergy = std::sqrt( mOriginal*mOriginal +
                                        targetMass*targetMass +
                                        2.0*targetMass*etOriginal );
  G4double availableEnergy = centerofmassEnergy-(targetMass+mOriginal);
    
  static G4bool first = true;
  const G4int numMul = 1200;
  const G4int numMulA = 400;
  const G4int numSec = 60;
  static G4double protmul[numMul], protnorm[numSec]; // proton constants
  static G4double neutmul[numMul], neutnorm[numSec]; // neutron constants
  static G4double protmulA[numMulA], protnormA[numSec]; // proton constants
  static G4double neutmulA[numMulA], neutnormA[numSec]; // neutron constants
 
  // npos = number of pi+, nneg = number of pi-, nzero = number of pi0
  G4int counter;
  G4int nt=0;
  G4int npos = 0, nneg = 0, nzero = 0;
  G4double test;
  const G4double c = 1.25;    
  const G4double b[] = { 0.70, 0.70 };
 
  if (first) {      // compute normalization constants (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; ++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];
    }
 
    // do the same for annihilation channels
    for( i=0; i<numMulA; ++i )protmulA[i] = 0.0;
    for( i=0; i<numSec; ++i )protnormA[i] = 0.0;
    counter = -1;
    for (npos = 1; npos < (numSec/3); ++npos) {
      nneg = npos-1;
      for (nzero = 0; nzero < numSec/3; ++nzero) {
        if (++counter < numMulA) {
          nt = npos+nneg+nzero;
          if (nt > 1 && nt <= numSec) {
            protmulA[counter] = Pmltpc(npos,nneg,nzero,nt,b[0],c);
            protnormA[nt-1] += protmulA[counter];
          }
        }
      }
    }
    for (i = 0; i < numMulA; ++i) neutmulA[i] = 0.0;
    for (i = 0; i < numSec; ++i) neutnormA[i] = 0.0;
    counter = -1;
    for (npos = 0; npos < numSec/3; ++npos) {
      nneg = npos;
      for (nzero = 0; nzero < numSec/3; ++nzero) {
        if (++counter < numMulA) {
          nt = npos+nneg+nzero;
          if (nt > 1 && nt <= numSec) {
            neutmulA[counter] = Pmltpc(npos,nneg,nzero,nt,b[1],c);
            neutnormA[nt-1] += neutmulA[counter];
          }
        }
      }
    }
    for (i = 0; i < numSec; ++i) {
      if (protnormA[i] > 0.0) protnormA[i] = 1.0/protnormA[i];
      if (neutnormA[i] > 0.0) neutnormA[i] = 1.0/neutnormA[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 *anAntiProton = G4AntiProton::AntiProton();
  G4ParticleDefinition *aPiPlus = G4PionPlus::PionPlus();
    
  // energetically possible to produce pion(s)  -->  inelastic scattering
  //                                   otherwise quasi-elastic scattering
    
  const G4double anhl[] = {1.00,1.00,1.00,1.00,1.00,1.00,1.00,1.00,0.97,0.88,
                           0.85,0.81,0.75,0.64,0.64,0.55,0.55,0.45,0.47,0.40,
                           0.39,0.36,0.33,0.10,0.01};
  G4int iplab = G4int( pOriginal/GeV*10.0 );
  if( iplab >  9 )iplab = G4int( (pOriginal/GeV- 1.0)*5.0 ) + 10;
  if( iplab > 14 )iplab = G4int(  pOriginal/GeV- 2.0 ) + 15;
  if( iplab > 22 )iplab = G4int( (pOriginal/GeV-10.0)/10.0 ) + 23;
  if( iplab > 24 )iplab = 24;
  if (G4UniformRand() > anhl[iplab]) {
    if (availableEnergy <= aPiPlus->GetPDGMass()/MeV) {
      quasiElastic = true;
      return;
    }
    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 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
      npos = nneg = nzero = 0;
      if (targetParticle.GetDefinition() == aProton) {
        test = std::exp(std::min(expxu,
                        std::max( expxl, -(1.0+b[0])*(1.0+b[0])/(2.0*c*c) ) ) );
        w0 = test;
        wp = test;
        if (G4UniformRand() < w0/(w0+wp) ) nzero = 1;
        else npos = 1;
      } else {
        // target is a neutron
        test = std::exp(std::min(expxu,
                        std::max( expxl, -(1.0+b[1])*(1.0+b[1])/(2.0*c*c) ) ) );
        w0 = test;
        wp = test;
        test = std::exp(std::min(expxu,
                        std::max( expxl, -(-1.0+b[1])*(-1.0+b[1])/(2.0*c*c) ) ) );
        wm = test;
        wt = w0+wp+wm;
        wp += w0;
        G4double ran = G4UniformRand();
        if( ran < w0/wt )
          nzero = 1;
        else if( ran < wp/wt )
          npos = 1;
        else
          nneg = 1;
      }
    } else {
      // (availableEnergy >= 2.0*GeV) || (random number < supp[ieab])
      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 && ran >= excs; ++nneg) {
            for (nzero = 0; nzero < numSec/3 && ran >= excs; ++nzero) {
              if (++counter < numMul) {
                nt = npos + nneg + nzero;
                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) {
          // 3 previous loops continued to the end
          quasiElastic = true;
          return;
        }
        npos--; nneg--; nzero--;
 
      } 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 >= 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) {
          // 3 previous loops continued to the end
          quasiElastic = true;
          return;
        }
        npos--; nneg--; nzero--;
      }
    }
 
    if (targetParticle.GetDefinition() == aProton) {
      switch (npos-nneg)
      {
       case 1:
         if( G4UniformRand() < 0.5 )
         {
           currentParticle.SetDefinitionAndUpdateE( anAntiProton );
           incidentHasChanged = true;
         }
         else
         {
           targetParticle.SetDefinitionAndUpdateE( aNeutron );
           targetHasChanged = true;
         }
         break;
       case 2:
         currentParticle.SetDefinitionAndUpdateE( anAntiProton );
         targetParticle.SetDefinitionAndUpdateE( aNeutron );
         incidentHasChanged = true;
         targetHasChanged = true;
         break;
       default:
         break;
      }
    } else {
      // target must be a neutron
      switch (npos-nneg)
      {
        case 0:
          if (G4UniformRand() < 0.33) {
             currentParticle.SetDefinitionAndUpdateE( anAntiProton );
             targetParticle.SetDefinitionAndUpdateE( aProton );
             incidentHasChanged = true;
             targetHasChanged = true;
          }
          break;
        case 1:
          currentParticle.SetDefinitionAndUpdateE( anAntiProton );
          incidentHasChanged = true;
          break;
        default:
          targetParticle.SetDefinitionAndUpdateE( aProton );
          targetHasChanged = true;
          break;
      }
    }
  } else {
    // random number <= anhl[iplab]
    if (centerofmassEnergy <= 2*aPiPlus->GetPDGMass()/MeV) {
      quasiElastic = true;
      return;
    }
 
    // annihilation channels
    G4double n, anpn;
    GetNormalizationConstant(-centerofmassEnergy, n, anpn);
    G4double ran = G4UniformRand();
    G4double dum, excs = 0.0;
    if (targetParticle.GetDefinition() == aProton) {
      counter = -1;
      for (npos = 1; (npos < numSec/3) && (ran>=excs); ++npos) {
        nneg = npos-1;
        for (nzero = 0; (nzero < numSec/3) && (ran>=excs); ++nzero) {
          if (++counter < numMulA) {
            nt = npos+nneg+nzero;
            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*protmulA[counter]*protnormA[nt-1]/(2.0*n*n);
              if (std::fabs(dum) < 1.0)
                {
                  if( test >= 1.0e-10 )excs += dum*test;
                }
                else
                  excs += dum*test;
              }
            }
          }
        }
    } else {
      // target must be a neutron
      counter = -1;
      for (npos = 0; (npos < numSec/3) && (ran >= excs); ++npos) {
        nneg = npos;
        for (nzero = 0; (nzero < numSec/3) && (ran >= excs); ++nzero) {
          if (++counter < numMulA) {
            nt = npos+nneg+nzero;
            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*neutmulA[counter]*neutnormA[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--; nzero--;
    currentParticle.SetMass( 0.0 );
    targetParticle.SetMass( 0.0 );
  }
 
  while(npos+nneg+nzero < 3) nzero++;
  SetUpPions(npos, nneg, nzero, vec, vecLen);
  return;
}