G4HEPionPlusInelastic.cc

Go to the documentation of this file.

//
// ********************************************************************
// * License and Disclaimer                                           *
// *                                                                  *
// * The  Geant4 software  is  copyright of the Copyright Holders  of *
// * the Geant4 Collaboration.  It is provided  under  the terms  and *
// * conditions of the Geant4 Software License,  included in the file *
// * LICENSE and available at  http://cern.ch/geant4/license .  These *
// * include a list of copyright holders.                             *
// *                                                                  *
// * Neither the authors of this software system, nor their employing *
// * institutes,nor the agencies providing financial support for this *
// * work  make  any representation or  warranty, express or implied, *
// * regarding  this  software system or assume any liability for its *
// * use.  Please see the license in the file  LICENSE  and URL above *
// * for the full disclaimer and the limitation of liability.         *
// *                                                                  *
// * This  code  implementation is the result of  the  scientific and *
// * technical work of the GEANT4 collaboration.                      *
// * By using,  copying,  modifying or  distributing the software (or *
// * any work based  on the software)  you  agree  to acknowledge its *
// * use  in  resulting  scientific  publications,  and indicate your *
// * acceptance of all terms of the Geant4 Software license.          *
// ********************************************************************
//
// $Id$
//
 
// 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.  
// First work done by J.L.Chuma and F.W.Jones, TRIUMF, June 96.  
// H. Fesefeldt, RWTH-Aachen, 23-October-1996
 
#include "G4HEPionPlusInelastic.hh"
#include "globals.hh"
#include "G4ios.hh"
#include "G4PhysicalConstants.hh"
 
void G4HEPionPlusInelastic::ModelDescription(std::ostream& outFile) const
{
  outFile << "G4HEPionPlusInelastic 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*
G4HEPionPlusInelastic::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 << "G4HEPionPlusInelastic: incident energy < 1 GeV" << G4endl;
 
  if (verboseLevel > 1) {
    G4cout << "G4HEPionPlusInelastic::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; 
    
  FirstIntInCasPionPlus(inElastic, availableEnergy, pv, vecLength,
                        incidentParticle, targetParticle, atomicWeight);
 
  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
G4HEPionPlusInelastic::FirstIntInCasPionPlus(G4bool& inElastic,
                                             const G4double availableEnergy,
                                             G4HEVector pv[],
                                             G4int& vecLen,
                                             const G4HEVector& incidentParticle,
                                             const G4HEVector& targetParticle,
                                             const G4double atomicWeight)
 
// 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 neutronCode = Neutron.getCode();
  G4int protonCode = Proton.getCode();
  G4double pionMass = PionPlus.getMass();
 
  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=Imax(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=Imax(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 places
                                              // the same as beam and target                                    
   pv[0] = incidentParticle;
   pv[1] = targetParticle;
   vecLen = 2;
 
   if( !inElastic ) 
     {                                     // quasi-elastic scattering, no pions produced
       if( targetCode == neutronCode ) 
         {
           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( Amin( 9.0, incidentTotalMomentum*5. ) );
           if( G4UniformRand() < cech[iplab]/std::pow(atomicWeight,0.42) ) 
             {                             // charge exchange  pi+ n -> pi0 p
               pv[0] = PionZero;
               pv[1] = Proton;
             }
         }
       return;
     }
   else if (availableEnergy <= pionMass)
       return;
 
//                                            inelastic scattering
 
   npos = 0, nneg = 0, nzero = 0;
   G4double eab = availableEnergy;
   G4int ieab = G4int( eab*5.0 );
   
   G4double supp[] = {0., 0.2, 0.45, 0.55, 0.65, 0.75, 0.85, 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 == protonCode )                    // target is a proton 
         {
           w0 = - sqr(1.+protb)/(2.*c*c);
           wp = w0 = std::exp(w0);
           if( G4UniformRand() < w0/(w0+wp) )  
             { npos = 0; nneg = 0; nzero = 1; }
           else 
             { npos = 1; nneg = 0; nzero = 0; }       
         } 
       else 
         {                                               // target is a neutron
           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( 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-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( 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=Imax(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( 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 == nneg)
         {
         }
       else if (npos == (1+nneg))
         {
           if( G4UniformRand() < 0.5)
             {
               pv[1] = Neutron;
             }
           else
             {
               pv[0] = PionZero;
             }
         }
       else      
         {
           pv[0] = PionZero;
           pv[1] = Neutron;
         } 
     }  
   else
     {
       if( npos == nneg)
         {
           if( G4UniformRand() < 0.25)
             {
               pv[0] = PionZero;
               pv[1] = Proton;
             }
           else
             {
             }
         } 
       else if ( npos == (1+nneg))
         {
           pv[0] = PionZero;
         }
       else
         {
           pv[1] = Proton;
         }
     }      
 
 
   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;
 }