G4HEPionMinusInelastic.cc

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// $Id$
//
// 11-OCT-2007 F.W. Jones: fixed incorrect Imax (should be Imin) in
//             sampling of charge exchange.
 
// 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.  
// First work done by J.L.Chuma and F.W.Jones, TRIUMF, June 96.  
// H. Fesefeldt, RWTH-Aachen, 23-October-1996
 
#include "G4HEPionMinusInelastic.hh"
#include "globals.hh"
#include "G4ios.hh"
#include "G4PhysicalConstants.hh"
 
void G4HEPionMinusInelastic::ModelDescription(std::ostream& outFile) const
{
  outFile << "G4HEPionMinusInelastic is one of the High Energy\n"
          << "Parameterized (HEP) models used to implement inelastic\n"
          << "pi- 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 pi- with initial energies\n"
          << "above 20 GeV.\n";
}
 
 
G4HadFinalState*
G4HEPionMinusInelastic::ApplyYourself(const G4HadProjectile& aTrack,
                                      G4Nucleus& targetNucleus)
{
  G4HEVector* pv = new G4HEVector[MAXPART];
  const G4HadProjectile* aParticle = &aTrack;
  const G4double A = targetNucleus.GetA_asInt();
  const G4double Z = targetNucleus.GetZ_asInt();
  G4HEVector incidentParticle(aParticle);
     
  G4double atomicNumber = Z;
  G4double atomicWeight = A;
 
  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 << "GHEPionMinusInelastic: incident energy < 1 GeV" << G4endl;
 
  if (verboseLevel > 1) {
    G4cout << "G4HEPionMinusInelastic::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;
 
  // The value of the inElastic flag was originally defined in the Gheisha
  // stand-alone code as follows: 
  //   G4bool inElastic = InElasticCrossSectionInFirstInt
  //                      (availableEnergy, incidentCode, incidentTotalMomentum);  
  // For unknown reasons, it was replaced by the following code in Geant
 
  G4bool inElastic = true;
  //    if (G4UniformRand() < elasticCrossSection/totalCrossSection) inElastic = false;    
 
  vecLength = 0;
        
  if (verboseLevel > 1)
    G4cout << "ApplyYourself: CallFirstIntInCascade for particle "
           << incidentCode << G4endl;
 
  G4bool successful = false; 
    
  FirstIntInCasPionMinus(inElastic, availableEnergy, pv, vecLength,
                         incidentParticle, targetParticle);
 
  if (verboseLevel > 1)
    G4cout << "ApplyYourself::StrangeParticlePairProduction" << G4endl;
 
  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;
 
  FillParticleChange(pv,  vecLength);
  delete [] pv;
  theParticleChange.SetStatusChange(stopAndKill);
  return &theParticleChange;
}
 
 
void
G4HEPionMinusInelastic::FirstIntInCasPionMinus(G4bool& inElastic,
                                               const G4double availableEnergy,
                                               G4HEVector pv[],
                                               G4int& vecLen,
                                               const G4HEVector& incidentParticle,
                                               const G4HEVector& targetParticle)
 
// Pion- 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 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-,  nero = number of pi0
 
  G4int i, counter, nt, npos, nneg, nero;
 
  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=Imax(0,npos-1); nneg<=(npos+1); nneg++ ) 
               {
                 for( nero=0; nero<numSec/3; nero++ ) 
                    {
                      if( ++counter < numMul ) 
                        {
                          nt = npos+nneg+nero;
                          if( (nt>0) && (nt<=numSec) ) 
                            {
                              protmul[counter] =
                                    pmltpc(npos,nneg,nero,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( nero=0; nero<numSec/3; nero++ ) 
                    {
                      if( ++counter < numMul ) 
                        {
                          nt = npos+nneg+nero;
                          if( (nt>0) && (nt<=numSec) ) 
                            {
                               neutmul[counter] =
                                      pmltpc(npos,nneg,nero,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 places
   // 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, nero = 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 cech[] = {1., 0.95, 0.79, 0.32, 0.19, 0.16, 0.14, 0.12, 0.10, 0.08};
       G4int iplab = Imin(9, G4int( incidentTotalMomentum*5.));
       if( G4UniformRand() < cech[iplab] )
         {
           if( targetCode == protonCode )
             {
               pv[0] = PionZero;
               pv[1] = Neutron;
               return;
             }
           else
             {
               return;
             }
         }
 
       G4double w0, wp, wm, wt, ran;
       if( targetCode == protonCode )                    // target is a proton 
         {
           w0 = - sqr(1.+protb)/(2.*c*c);
           wp = w0 = std::exp(w0);
           wm = - sqr(-1.+protb)/(2.*c*c);
           wm = std::exp(wm);
           wp *= 10.;
           wt = w0+wp+wm;
           wp = w0+wp;
           ran = G4UniformRand();
           if( ran < w0/wt )  
             { npos = 0; nneg = 0; nero = 1; }
           else if ( ran < wp/wt )
             { npos = 1; nneg = 0; nero = 0; }
           else
             { npos = 0; nneg = 1; nero = 0; }       
         } 
       else 
         {                                           // target is a neutron
           w0 = -sqr(1.+neutb)/(2.*c*c);
           wm = -sqr(-1.+neutb)/(2.*c*c);
           w0 = std::exp(w0);
           wm = std::exp(wm);
           if( G4UniformRand() < w0/(w0+wm) )
             { npos = 0; nneg = 0; nero = 1; }       
           else
             { npos = 0; nneg = 1; nero = 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( Amin( expxu, Amax( 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=Imax(0,npos-1); nneg<=(npos+1); nneg++) {
               for (nero=0; nero<numSec/3; nero++) {
                 if (++counter < numMul) {
                   nt = npos+nneg+nero;
                   if ( (nt>0) && (nt<=numSec) ) {
                     test = std::exp( Amin( expxu, Amax( 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 (nero=0; nero<numSec/3; nero++) {
                 if (++counter < numMul) {
                   nt = npos+nneg+nero;
                   if ( (nt>=1) && (nt<=numSec) ) {
                     test = std::exp( Amin( expxu, Amax( 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 == (1+nneg))
         {
           pv[1] = Neutron;
         }
       else if (npos == nneg)
         {
           if( G4UniformRand() < 0.75)
             {
             }
           else
             {
               pv[0] = PionZero;
               pv[1] = Neutron;
             }
         }
       else      
         {
           pv[0] = PionZero;
         } 
     }  
   else
     {
       if( npos == (nneg-1))
         {
           if( G4UniformRand() < 0.5)
             {
               pv[1] = Proton;
             }
           else
             {
               pv[0] = PionZero;
             }
         } 
       else if ( npos == nneg)
         {
         }
       else
         {
           pv[0] = PionZero;
           pv[1] = Proton;
         }
     }      
 
 
   nt = npos + nneg + nero;
   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( nero > 0 )
                { 
                  pv[vecLen++] = PionZero;
                  nero--;
                }
            }
         nt = npos + nneg + nero;
       } 
   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;
 }