G4INCLPionResonanceDecayChannel.cc

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//
// INCL++ intra-nuclear cascade model
// Alain Boudard, CEA-Saclay, France
// Joseph Cugnon, University of Liege, Belgium
// Jean-Christophe David, CEA-Saclay, France
// Pekka Kaitaniemi, CEA-Saclay, France, and Helsinki Institute of Physics, Finland
// Sylvie Leray, CEA-Saclay, France
// Davide Mancusi, CEA-Saclay, France
//
#define INCLXX_IN_GEANT4_MODE 1

#include "globals.hh"

#include "G4INCLPionResonanceDecayChannel.hh"
#include "G4INCLKinematicsUtils.hh"
#include "G4INCLBinaryCollisionAvatar.hh"
#include "G4INCLRandom.hh"
#include "G4INCLGlobals.hh"
#include "G4INCLPhaseSpaceGenerator.hh"
// #include <cassert>


namespace G4INCL {
  
  const G4double PionResonanceDecayChannel::angularSlope = 0.; // Slope to be defined, if needed.
  
  PionResonanceDecayChannel::PionResonanceDecayChannel(Particle *p, ThreeVector const &dir)
    :theParticle(p), incidentDirection(dir)
  { }
  
  PionResonanceDecayChannel::~PionResonanceDecayChannel() {}
  
//  Decay during the intranuclear cascade for Omega only
  G4double PionResonanceDecayChannel::computeDecayTime(Particle *p) {
  const G4double m = p->getMass();
  const G4double geff = p->getEnergy()/m;
//    const G4double geta = 1.31e-3;
    const G4double gomega = 8.49;
    G4double gg=0.;
    switch (p->getType()) {
/*      case Eta:
        gg=geta;
        break;*/
      case Omega:
        gg=gomega;
        break;
      default:
        INCL_FATAL("Unrecognized pion resonance type; type=" << p->getType() << '\n');
        break;
    }
    const G4double tpires = -G4INCL::PhysicalConstants::hc/gg*std::log(Random::shoot())*geff;
    return tpires;
  }
  
  void PionResonanceDecayChannel::sampleAngles(G4double *ctet_par, G4double *stet_par, G4double *phi_par) {

    (*ctet_par) = -1.0 + 2.0*Random::shoot();
    if(std::abs(*ctet_par) > 1.0) (*ctet_par) = Math::sign(*ctet_par);
    (*stet_par) = std::sqrt(1.-(*ctet_par)*(*ctet_par));
    (*phi_par) = Math::twoPi * Random::shoot();
  }
  
  void PionResonanceDecayChannel::fillFinalState(FinalState *fs) {
    
    ParticleType createdType;
    ParticleType pionType1=Neutron; // to avoid forgetting pionType definition when 3 particles are emitted
    ParticleType pionType2=Neutron; 

    const G4double sqrtS = theParticle->getMass();
    G4int nbpart = 3; // number of emitted particles
    G4double drnd=Random::shoot();
    switch (theParticle->getType()) {
      case Eta:
        if (drnd < 0.3972) { // renormalized to the only four decays taken into account here
//    2 photons
          nbpart=2;
          theParticle->setType(Photon);
          createdType = Photon;
        }
        else if (drnd < 0.7265) {
//    3 pi0
          theParticle->setType(PiZero);
          pionType1 = PiZero;
          pionType2 = PiZero;
        }
        else if (drnd < 0.9575) {
//    pi+ pi- pi0
        theParticle->setType(PiZero);
        pionType1 = PiPlus;
        pionType2 = PiMinus;
      }
        else {
//    pi+ pi- photon
          theParticle->setType(Photon);
          pionType1 = PiPlus;
          pionType2 = PiMinus;
        }
      break;
      case Omega:
        if (drnd < 0.9009) { // renormalized to the only three decays taken into account here
//    pi+ pi- pi0
          theParticle->setType(PiZero);
          pionType1 = PiPlus;
          pionType2 = PiMinus;
        }
        else if (drnd < 0.9845) {
//    pi0 photon
          nbpart=2;
          theParticle->setType(PiZero);
          createdType = Photon;
        }
        else {
//    pi+ pi-
          nbpart=2;
          theParticle->setType(PiPlus);
          createdType = PiMinus;
        }
        break;
      default:
        INCL_FATAL("Unrecognized pion resonance type; type=" << theParticle->getType() << '\n');
        break;
    }

    if (nbpart == 2) {      
      G4double fi, ctet, stet;
      sampleAngles(&ctet, &stet, &fi);
      
      G4double cfi = std::cos(fi);
      G4double sfi = std::sin(fi);
      G4double beta = incidentDirection.mag();
      
      G4double q1, q2, q3;
      G4double sal=0.0;
      if (beta >= 1.0e-10)
        sal = incidentDirection.perp()/beta;
      if (sal >= 1.0e-6) {
        G4double b1 = incidentDirection.getX();
        G4double b2 = incidentDirection.getY();
        G4double b3 = incidentDirection.getZ();
        G4double cal = b3/beta;
        G4double t1 = ctet+cal*stet*sfi/sal;
        G4double t2 = stet/sal;
        q1=(b1*t1+b2*t2*cfi)/beta;
        q2=(b2*t1-b1*t2*cfi)/beta;
        q3=(b3*t1/beta-t2*sfi);
      } else {
        q1 = stet*cfi;
        q2 = stet*sfi;
        q3 = ctet;
      }
            
      G4double xq = KinematicsUtils::momentumInCM(sqrtS,
                            theParticle->getMass(),
                            ParticleTable::getINCLMass(createdType));
      q1 *= xq;
      q2 *= xq;
      q3 *= xq;
      
      ThreeVector createdMomentum(q1, q2, q3);
      ThreeVector createdPosition(theParticle->getPosition());
      Particle *createdParticle = new Particle(createdType, createdMomentum, createdPosition);
      theParticle->setMomentum(-createdMomentum);
      theParticle->adjustEnergyFromMomentum();
      
      fs->addModifiedParticle(theParticle);
      fs->addCreatedParticle(createdParticle);
      
    }
    else if (nbpart == 3) {
// assert(pionType1!=Neutron && pionType2!=Neutron);
      ParticleList list;
      list.push_back(theParticle);
      const ThreeVector &rposdecay = theParticle->getPosition();
      const ThreeVector zero;
      Particle *Pion1 = new Particle(pionType1,zero,rposdecay);
      Particle *Pion2 = new Particle(pionType2,zero,rposdecay);
      list.push_back(Pion1);
      list.push_back(Pion2);
      
      fs->addModifiedParticle(theParticle);
      fs->addCreatedParticle(Pion1);
      fs->addCreatedParticle(Pion2);

      //      PhaseSpaceGenerator::generateBiased(sqrtS, list, 0, angularSlope); Biasing?
      PhaseSpaceGenerator::generate(sqrtS, list);
    }

  }
}