G4HEKaonZeroShortInelastic.cc

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// $Id$
//

// G4 Process: Gheisha High Energy Collision model.
// This includes the high energy cascading model, the two-body-resonance model
// and the low energy two-body model. Not included are the low energy stuff
// like nuclear reactions, nuclear fission without any cascading and all
// processes for particles at rest.
//  
// New version by D.H. Wright (SLAC) to fix seg fault in old version
// 21 January 2010

#include "G4HEKaonZeroShortInelastic.hh"
#include "globals.hh"
#include "G4ios.hh"
#include "G4PhysicalConstants.hh"

void G4HEKaonZeroShortInelastic::ModelDescription(std::ostream& outFile) const
{
  outFile << "G4HEKaonZeroShortInelastic is one of the High Energy\n"
          << "Parameterized (HEP) models used to implement inelastic\n"
          << "K0S 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 K0S with initial energies\n"
          << "above 20 GeV.\n";
}


G4HadFinalState*
G4HEKaonZeroShortInelastic::ApplyYourself(const G4HadProjectile& aTrack,
                                          G4Nucleus& targetNucleus)
{
  G4HEVector* pv = new G4HEVector[MAXPART];
  const G4HadProjectile* aParticle = &aTrack;
  const G4double atomicWeight = targetNucleus.GetA_asInt();
  const G4double atomicNumber = targetNucleus.GetZ_asInt();
  G4HEVector incidentParticle(aParticle);

  G4int incidentCode = incidentParticle.getCode();
  G4double incidentMass = incidentParticle.getMass();
  G4double incidentTotalEnergy = incidentParticle.getEnergy();

  // G4double incidentTotalMomentum = incidentParticle.getTotalMomentum();
  // DHW 19 May 2011: variable set but not used

  G4double incidentKineticEnergy = incidentTotalEnergy - incidentMass;

  if(incidentKineticEnergy < 1)
    G4cout << "GHEKaonZeroShortInelastic: incident energy < 1 GeV" << G4endl;

  if(verboseLevel > 1) {
    G4cout << "G4HEKaonZeroShortInelastic::ApplyYourself" << G4endl;
    G4cout << "incident particle " << incidentParticle.getName()
           << "mass "              << incidentMass
           << "kinetic energy "    << incidentKineticEnergy
           << G4endl;
    G4cout << "target material with (A,Z) = (" 
           << atomicWeight << "," << atomicNumber << ")" << G4endl;
  }
    
  G4double inelasticity = NuclearInelasticity(incidentKineticEnergy, 
                                              atomicWeight, atomicNumber);
  if(verboseLevel > 1)
    G4cout << "nuclear inelasticity = " << inelasticity << G4endl;
    
  incidentKineticEnergy -= inelasticity;
    
  G4double excitationEnergyGNP = 0.;
  G4double excitationEnergyDTA = 0.; 

  G4double excitation = NuclearExcitation(incidentKineticEnergy,
                                          atomicWeight, atomicNumber,
                                          excitationEnergyGNP,
                                          excitationEnergyDTA);
  if(verboseLevel > 1)
    G4cout << "nuclear excitation = " << excitation << excitationEnergyGNP 
           << excitationEnergyDTA << G4endl;             

  incidentKineticEnergy -= excitation;
  incidentTotalEnergy = incidentKineticEnergy + incidentMass;
  // incidentTotalMomentum = std::sqrt( (incidentTotalEnergy-incidentMass)                    
  //                                   *(incidentTotalEnergy+incidentMass));
  // DHW 19 May 2011: variable set but not used

  G4HEVector targetParticle;
  if(G4UniformRand() < atomicNumber/atomicWeight) { 
    targetParticle.setDefinition("Proton");
  } else { 
    targetParticle.setDefinition("Neutron");
  }

  G4double targetMass = targetParticle.getMass();
  G4double centerOfMassEnergy = std::sqrt(incidentMass*incidentMass
                                        + targetMass*targetMass
                                        + 2.0*targetMass*incidentTotalEnergy);
  G4double availableEnergy = centerOfMassEnergy - targetMass - incidentMass;

  G4bool inElastic = true;
  vecLength = 0;           
        
  if(verboseLevel > 1)
    G4cout << "ApplyYourself: CallFirstIntInCascade for particle "
           << incidentCode << G4endl;

  G4bool successful = false; 
    
  // Split K0L into K0 and K0bar
  if (G4UniformRand() < 0.5)
    FirstIntInCasAntiKaonZero(inElastic, availableEnergy, pv, vecLength,
                              incidentParticle, targetParticle );
  else
    FirstIntInCasKaonZero(inElastic, availableEnergy, pv, vecLength,
                          incidentParticle, targetParticle, atomicWeight );

  // Do nuclear interaction with either K0 or K0bar 
  if ((vecLength > 0) && (availableEnergy > 1.)) 
    StrangeParticlePairProduction(availableEnergy, centerOfMassEnergy,
                                  pv, vecLength,
                                  incidentParticle, targetParticle);

  HighEnergyCascading(successful, pv, vecLength,
                      excitationEnergyGNP, excitationEnergyDTA,
                      incidentParticle, targetParticle,
                      atomicWeight, atomicNumber);
  if (!successful)
    HighEnergyClusterProduction(successful, pv, vecLength,
                                excitationEnergyGNP, excitationEnergyDTA,
                                incidentParticle, targetParticle,
                                atomicWeight, atomicNumber);
  if (!successful) 
    MediumEnergyCascading(successful, pv, vecLength, 
                          excitationEnergyGNP, excitationEnergyDTA, 
                          incidentParticle, targetParticle,
                          atomicWeight, atomicNumber);

  if (!successful)
    MediumEnergyClusterProduction(successful, pv, vecLength,
                                  excitationEnergyGNP, excitationEnergyDTA,       
                                  incidentParticle, targetParticle,
                                  atomicWeight, atomicNumber);
  if (!successful)
    QuasiElasticScattering(successful, pv, vecLength,
                           excitationEnergyGNP, excitationEnergyDTA,
                           incidentParticle, targetParticle, 
                           atomicWeight, atomicNumber);

  if (!successful) 
    ElasticScattering(successful, pv, vecLength,
                      incidentParticle,    
                      atomicWeight, atomicNumber);

  if (!successful) 
    G4cout << "GHEInelasticInteraction::ApplyYourself fails to produce final state particles"
           << G4endl;

  // Check for K0, K0bar and change particle types to K0L, K0S if necessary
  G4int kcode;
  for (G4int i = 0; i < vecLength; i++) {
    kcode = pv[i].getCode();
    if (kcode == KaonZero.getCode() || kcode == AntiKaonZero.getCode()) {
      if (G4UniformRand() < 0.5) 
        pv[i] = KaonZeroShort; 
      else
        pv[i] = KaonZeroLong;
    }
  } 

  //      ................
 
  FillParticleChange(pv,  vecLength);
  delete [] pv;
  theParticleChange.SetStatusChange(stopAndKill);
  return &theParticleChange;
}


void
G4HEKaonZeroShortInelastic::FirstIntInCasKaonZero(G4bool& inElastic,
                                                  const G4double availableEnergy,
                                                  G4HEVector pv[],
                                                  G4int& vecLen,
                                                  const G4HEVector& incidentParticle,
                                                  const G4HEVector& targetParticle,
                                                  const G4double atomicWeight)

// Kaon0 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.
{
  static const G4double expxu = 82.;     // upper bound for arg. of exp
  static const G4double expxl = -expxu;  // lower bound for arg. of exp

  static const G4double protb = 0.7;
  static const G4double neutb = 0.7;
  static const G4double c = 1.25;

  static const G4int numMul = 1200;
  static const G4int numSec = 60;

  G4int neutronCode = Neutron.getCode();
  G4int protonCode  = Proton.getCode();

  G4int targetCode = targetParticle.getCode();
  G4double incidentTotalMomentum = incidentParticle.getTotalMomentum();

  static G4bool first = true;
  static G4double protmul[numMul], protnorm[numSec];  // proton constants
  static G4double neutmul[numMul], neutnorm[numSec];  // neutron constants

  // misc. local variables
  // npos = number of pi+,  nneg = number of pi-,  nzero = number of pi0

  G4int i, counter, nt, npos, nneg, nzero;

  if (first) {
    // compute normalization constants, this will only be done once
    first = false;
    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-1); 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,protb,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=npos; 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,neutb,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


  // Initialize the first two particles
  // the same as beam and target
  pv[0] = incidentParticle;
  pv[1] = targetParticle;
  vecLen = 2;

  if( !inElastic ) {
    // quasi-elastic scattering, no pions produced
    if( targetCode == protonCode) {
      G4double cech[] = {0.33,0.27,0.29,0.31,0.27,0.18,0.13,0.10,0.09,0.07};
      G4int iplab = G4int( std::min( 9.0, incidentTotalMomentum*5. ) );
      if( G4UniformRand() < cech[iplab]/std::pow(atomicWeight,0.42)) {
        // charge exchange  K+ n -> K0 p
        pv[0] = KaonPlus;
        pv[1] = Neutron;
      }
    }
    return;
  } else if (availableEnergy <= PionPlus.getMass()) {
    return;
  }

  // Inelastic scattering

  npos = 0, nneg = 0, nzero = 0;
  G4double eab = availableEnergy;
  G4int ieab = G4int( eab*5.0 );

  G4double supp[] = {0., 0.4, 0.55, 0.65, 0.75, 0.82, 0.86, 0.90, 0.94, 0.98};
  if( (ieab <= 9) && (G4UniformRand() >=  supp[ieab])) {
    // Suppress high multiplicity events at low momentum
    // only one additional pion will be produced
    G4double w0, wp, wm, wt, ran;
    if (targetCode == neutronCode) {
      // target is a neutron
      w0 = - sqr(1.+protb)/(2.*c*c);
      w0 = std::exp(w0);
      wm = - sqr(-1.+protb)/(2.*c*c);
      wm = std::exp(wm);
      w0 = w0/2.;
      wm = wm*1.5;
      if (G4UniformRand() < w0/(w0+wm) ) {
        npos = 0;
        nneg = 0;
        nzero = 1;
      } else {
        npos = 0;
        nneg = 1;
        nzero = 0;
      }

    } else {
      // target is a proton
      w0 = -sqr(1.+neutb)/(2.*c*c);
      wp = w0 = std::exp(w0);
      wm = -sqr(-1.+neutb)/(2.*c*c);
      wm = std::exp(wm);
      wt = w0+wp+wm;
      wp = w0+wp;
      ran = G4UniformRand();
      if ( ran < w0/wt) {
        npos = 0;
        nneg = 0;
        nzero = 1;
      } else if (ran < wp/wt) {
        npos = 1;
        nneg = 0;
        nzero = 0;
      } else {
        npos = 0;
        nneg = 1;
        nzero = 0;
      }
    }
  } else {
    // number of total particles vs. centre of mass Energy - 2*proton mass

    G4double aleab = std::log(availableEnergy);
    G4double n = 3.62567+aleab*(0.665843+aleab*(0.336514
                 + aleab*(0.117712+0.0136912*aleab))) - 2.0;

    // Normalization constant for kno-distribution.
    // Calculate first the sum of all constants, check for numerical problems.
    G4double test, dum, anpn = 0.0;

       for (nt=1; nt<=numSec; nt++) {
         test = std::exp( std::min( expxu, std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
         dum = pi*nt/(2.0*n*n);
         if (std::fabs(dum) < 1.0) {
           if( test >= 1.0e-10 )anpn += dum*test;
         } else {
           anpn += dum*test;
         }
       }

       G4double ran = G4UniformRand();
       G4double excs = 0.0;
       if( targetCode == protonCode )
         {
           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) ) {
                           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) goto outOfLoop;      //----------------------->
                         }
                       }
                     }
                   }
              }

                                     // 3 previous loops continued to the end
           inElastic = false;                 // quasi-elastic scattering
           return;
         }
       else
         {                                         // target must be a neutron
           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>=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) goto outOfLoop;       // -------------------------->
                         }
                       }
                     }
                   }
              }
                                                  // 3 previous loops continued to the end
           inElastic = false;                     // quasi-elastic scattering.
           return;
         }
     }
   outOfLoop:           //  <-----------------------------------------------

   if( targetCode == neutronCode)
     {
       if( npos == nneg)
         {
         }
       else if (npos == (nneg-1))
         {
           if( G4UniformRand() < 0.5)
             {
               pv[0] = KaonPlus;
             }
           else
             {
               pv[1] = Proton;
             }
         }
       else
         {
           pv[0] = KaonPlus;
           pv[1] = Proton;
         }
     }
   else
     {
       if( npos == nneg )
         {
           if( G4UniformRand() < 0.25)
             {
               pv[0] = KaonPlus;
               pv[1] = Neutron;
             }
           else
             {
             }
         }
       else if ( npos == (nneg+1))
         {
           pv[1] = Neutron;
         }
       else
         {
           pv[0] = KaonPlus;
         }
     }

  nt = npos + nneg + nzero;
  while (nt > 0) {
    G4double ran = G4UniformRand();
    if (ran < (G4double)npos/nt) {
      if (npos > 0) {
        pv[vecLen++] = PionPlus;
        npos--;
      }
    } else if ( ran < (G4double)(npos+nneg)/nt) {
      if (nneg > 0) {
        pv[vecLen++] = PionMinus;
        nneg--;
      }
    } else {
      if (nzero > 0) {
        pv[vecLen++] = PionZero;
        nzero--;
      }
    }
    nt = npos + nneg + nzero;
  }

  if (verboseLevel > 1) {
    G4cout << "Particles produced: " ;
    G4cout << pv[0].getName() << " " ;
    G4cout << pv[1].getName() << " " ;
    for (i=2; i < vecLen; i++) G4cout << pv[i].getName() << " " ;
    G4cout << G4endl;
  }

  return;
}


void
G4HEKaonZeroShortInelastic::FirstIntInCasAntiKaonZero(G4bool& inElastic,
                                                      const G4double availableEnergy,
                                                      G4HEVector pv[],
                                                      G4int& vecLen,
                                                      const G4HEVector& incidentParticle,
                                                      const G4HEVector& targetParticle)

// AntiKaon0 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.
{
  static const G4double expxu = 82.;     // upper bound for arg. of exp
  static const G4double expxl = -expxu;  // lower bound for arg. of exp

  static const G4double protb = 0.7;
  static const G4double neutb = 0.7;
  static const G4double c = 1.25;

  static const G4int numMul = 1200;
  static const G4int numSec = 60;

  G4int neutronCode = Neutron.getCode();
  G4int protonCode = Proton.getCode();
  G4int kaonMinusCode = KaonMinus.getCode();
  G4int kaonZeroCode = KaonZero.getCode();
  G4int antiKaonZeroCode = AntiKaonZero.getCode();  

  G4int targetCode = targetParticle.getCode();
  G4double incidentTotalMomentum = incidentParticle.getTotalMomentum();

  static G4bool first = true;
  static G4double protmul[numMul], protnorm[numSec];  // proton constants
  static G4double neutmul[numMul], neutnorm[numSec];  // neutron constants

  // misc. local variables
  // npos = number of pi+,  nneg = number of pi-,  nzero = number of pi0

  G4int i, counter, nt, npos, nneg, nzero;

  if (first) {
    // compute normalization constants, this will only be done once
    first = false;
    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,protb,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,neutb,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

  // initialize the first two particles
  // the same as beam and target                                    
  pv[0] = incidentParticle;
  pv[1] = targetParticle;
  vecLen = 2;

  if (!inElastic || (availableEnergy <= PionPlus.getMass())) 
    return;
                                        
  // Inelastic scattering

  npos = 0, nneg = 0, nzero = 0;
  G4double cech[] = { 1., 1., 1., 0.70, 0.60, 0.55, 0.35, 0.25, 0.18, 0.15};
  G4int iplab = G4int( incidentTotalMomentum*5.);
  if( (iplab < 10) && (G4UniformRand() < cech[iplab]) ) {
    G4int ipl = std::min(19, G4int( incidentTotalMomentum*5.));
    G4double cnk0[] = {0.17, 0.18, 0.17, 0.24, 0.26, 0.20, 0.22, 0.21, 0.34, 0.45,
                       0.58, 0.55, 0.36, 0.29, 0.29, 0.32, 0.32, 0.33, 0.33, 0.33};
    if(G4UniformRand() < cnk0[ipl]) {
      if(targetCode == protonCode) {
        return;
      } else {
        pv[0] = KaonMinus;
        pv[1] = Proton;
        return;
      }
    }

    G4double ran = G4UniformRand();
    if(targetCode == protonCode) {

      // target is a proton 
      if( ran < 0.25 ) {
        ; 
      } else if (ran < 0.50) {
        pv[0] = PionPlus;
        pv[1] = SigmaZero;
      } else if (ran < 0.75) {
        ;
      } else {
        pv[0] = PionPlus;
        pv[1] = Lambda;
      }
    } else {

      // target is a neutron
      if( ran < 0.25 ) { 
        pv[0] = PionMinus;
        pv[1] = SigmaPlus;
      } else if (ran < 0.50) {
        pv[0] = PionZero;
        pv[1] = SigmaZero;
      } else if (ran < 0.75) { 
        pv[0] = PionPlus;
        pv[1] = SigmaMinus;
      } else {
        pv[0] = PionZero;
        pv[1] = Lambda;
      }
    }
    return;

  } else {
    // number of total particles vs. centre of mass Energy - 2*proton mass
   
    G4double aleab = std::log(availableEnergy);
    G4double n = 3.62567+aleab*(0.665843+aleab*(0.336514
                 + aleab*(0.117712+0.0136912*aleab))) - 2.0;
   
    // Normalization constant for kno-distribution.
    // Calculate first the sum of all constants, check for numerical problems.   
    G4double test, dum, anpn = 0.0;

    for (nt=1; nt<=numSec; nt++) {
      test = std::exp( std::min( expxu, std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
      dum = pi*nt/(2.0*n*n);
      if (std::fabs(dum) < 1.0) { 
        if( test >= 1.0e-10 )anpn += dum*test;
      } else { 
        anpn += dum*test;
      }
    }
   
    G4double ran = G4UniformRand();
    G4double excs = 0.0;
    if (targetCode == protonCode) {
      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) ) {
                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) goto outOfLoop;      //----------------------->
              }
            }
          }
        }
      }
                            // 3 previous loops continued to the end
      inElastic = false;    // quasi-elastic scattering   
      return;

    } else {         // target must be a neutron
      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>=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) goto outOfLoop;   // -------------------------->
              }
            }
          }
        }
      }
                              // 3 previous loops continued to the end
      inElastic = false;      // quasi-elastic scattering.
      return;
    }
  } 
  outOfLoop:   //  <------------------------------------------------------------------------   
    
  if( targetCode == protonCode)
     {
       if( npos == nneg)
         {
         }
       else if (npos == (1+nneg))
         {
           if( G4UniformRand() < 0.5)
             {
               pv[0] = KaonMinus;
             }
           else
             {
               pv[1] = Neutron;
             }
         }
       else      
         {
           pv[0] = KaonMinus;
           pv[1] = Neutron;
         } 
     }  
  else
     {
       if( npos == nneg)
         {
           if( G4UniformRand() < 0.75)
             {
             }
           else
             {
               pv[0] = KaonMinus;
               pv[1] = Proton;
             }
         } 
       else if ( npos == (1+nneg))
         {
           pv[0] = KaonMinus;
         }
       else
         {
           pv[1] = Proton;
         }
     }      


  if( G4UniformRand() < 0.5 )   
     {
       if(    (    (pv[0].getCode() == kaonMinusCode)
                && (pv[1].getCode() == neutronCode)  )
           || (    (pv[0].getCode() == kaonZeroCode)
                && (pv[1].getCode() == protonCode)   )
           || (    (pv[0].getCode() == antiKaonZeroCode)
                && (pv[1].getCode() == protonCode)   )   )
         {
           G4double ran = G4UniformRand();
           if( pv[1].getCode() == protonCode)
             { 
               if(ran < 0.68)
                 {
                   pv[0] = PionPlus;
                   pv[1] = Lambda;
                 }
               else if (ran < 0.84)
                 {
                   pv[0] = PionZero;
                   pv[1] = SigmaPlus;
                 }
               else
                 {
                   pv[0] = PionPlus;
                   pv[1] = SigmaZero;
                 }
             }
           else
             {
               if(ran < 0.68)
                 {
                   pv[0] = PionMinus;
                   pv[1] = Lambda;
                 }
               else if (ran < 0.84)
                 {
                   pv[0] = PionMinus;
                   pv[1] = SigmaZero;
                 }
               else
                 {
                   pv[0] = PionZero;
                   pv[1] = SigmaMinus;
                 }
             }
         } 
       else
         {
           G4double ran = G4UniformRand();
           if (ran < 0.67)
              {
                pv[0] = PionZero;
                pv[1] = Lambda;
              }
           else if (ran < 0.78)
              {
                pv[0] = PionMinus;
                pv[1] = SigmaPlus;
              }
           else if (ran < 0.89)
              {
                pv[0] = PionZero;
                pv[1] = SigmaZero;
              }
           else
              {
                pv[0] = PionPlus;
                pv[1] = SigmaMinus;
              }
         }
    }

  nt = npos + nneg + nzero;
  while ( nt > 0) {
    G4double ran = G4UniformRand();
    if ( ran < (G4double)npos/nt) { 
      if( npos > 0 ) {
        pv[vecLen++] = PionPlus;
        npos--;
      }
    } else if (ran < (G4double)(npos+nneg)/nt) {   
      if( nneg > 0 ) { 
        pv[vecLen++] = PionMinus;
        nneg--;
      }
    } else {
      if( nzero > 0 ) { 
        pv[vecLen++] = PionZero;
        nzero--;
      }
    }
    nt = npos + nneg + nzero;
  }
 
  if (verboseLevel > 1) {
    G4cout << "Particles produced: " ;
    G4cout << pv[0].getName() << " " ;
    G4cout << pv[1].getName() << " " ;
    for (i=2; i < vecLen; i++) G4cout << pv[i].getName() << " " ;
    G4cout << G4endl;
  }

  return;
}

---