G4RPGAntiNeutronInelastic.cc

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// $Id$
//
 
#include "G4RPGAntiNeutronInelastic.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"

G4HadFinalState*
G4RPGAntiNeutronInelastic::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 << "G4RPGAntiNeutronInelastic::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 );
    
  delete originalTarget;
  return &theParticleChange;
}

 
void G4RPGAntiNeutronInelastic::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 CASNB
  // 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

  // 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[] = { 0.70, 0.70 };
  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; ++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+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];
      }
      //
      // 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( np=1; np<(numSec/3); ++np )
      {
        nneg = np-1;
        for( nz=0; nz<numSec/3; ++nz )
        {
          if( ++counter < numMulA )
          {
            nt = np+nneg+nz;
            if( nt>1 && nt<=numSec )
            {
              protmulA[counter] = Pmltpc(np,nneg,nz,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( np=0; np<numSec/3; ++np )
      {
        nneg = np;
        for( nz=0; nz<numSec/3; ++nz )
        {
          if( ++counter < numMulA )
          {
            nt = np+nneg+nz;
            if( nt>1 && nt<=numSec )
            {
              neutmulA[counter] = Pmltpc(np,nneg,nz,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
        //
        np = nneg = nz = 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) )
            nz = 1;
          else
            np = 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 )
            nz = 1;
          else if( ran < wp/wt )
            np = 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( 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 )  // 3 previous loops continued to the end
          {
            quasiElastic = true;
            return;
          }
          np--; nneg--; nz--;
        }
        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+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 )  // 3 previous loops continued to the end
          {
            quasiElastic = true;
            return;
          }
          np--; nneg--; nz--;
        }
      }
      if( targetParticle.GetDefinition() == aProton )
      {
        switch( np-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( np-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( np=1; (np<numSec/3) && (ran>=excs); ++np )
        {
          nneg = np-1;
          for( nz=0; (nz<numSec/3) && (ran>=excs); ++nz )
          {
            if( ++counter < numMulA )
            {
              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*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( np=0; (np<numSec/3) && (ran>=excs); ++np )
        {
          nneg = np;
          for( nz=0; (nz<numSec/3) && (ran>=excs); ++nz )
          {
            if( ++counter < numMulA )
            {
              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*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;
      }
      np--; nz--;
      currentParticle.SetMass( 0.0 );
      targetParticle.SetMass( 0.0 );
    }
    while(np+nneg+nz<3) nz++;

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

 /* end of file */
 

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