G4INCLSigmaZeroDecayChannel.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 "G4INCLSigmaZeroDecayChannel.hh"
#include "G4INCLKinematicsUtils.hh"
#include "G4INCLBinaryCollisionAvatar.hh"
#include "G4INCLRandom.hh"
#include "G4INCLGlobals.hh"

namespace G4INCL {
  
  SigmaZeroDecayChannel::SigmaZeroDecayChannel(Particle *p, ThreeVector const &dir)
    :theParticle(p), incidentDirection(dir)
  {}
  
  SigmaZeroDecayChannel::~SigmaZeroDecayChannel() {}
  
  
  G4double SigmaZeroDecayChannel::computeDecayTime(Particle *p) {
// assert(p->getType() == SigmaZero);
    const G4double gamma = std::sqrt(1+std::pow(p->getMomentum().mag()/p->getMass(),2));
    const G4double tau = ParticleTable::getWidth(SigmaZero)*3E8*1E15*gamma; // fm
    const G4double t = -tau * std::log(Random::shoot());
    return t;
  }

  void SigmaZeroDecayChannel::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); // needed?
    (*stet_par) = std::sqrt(1.-(*ctet_par)*(*ctet_par));
    (*phi_par) = Math::twoPi * Random::shoot();
  }
  
  void SigmaZeroDecayChannel::fillFinalState(FinalState *fs) {
    
// assert( theParticle->getType() == SigmaZero);
    ParticleType createdType = Photon;
    
    const G4double sqrtS = theParticle->getMass();
    
    theParticle->setType(Lambda);
    G4double phi, c_tet, s_tet;
    sampleAngles(&c_tet, &s_tet, &phi);
    
    G4double c_phi = std::cos(phi);
    G4double s_phi = std::sin(phi);
    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 = c_tet+cal*s_tet*s_phi/sal;
      G4double t2 = s_tet/sal;
      q1=(b1*t1+b2*t2*c_phi)/beta;
      q2=(b2*t1-b1*t2*c_phi)/beta;
      q3=(b3*t1/beta-t2*s_phi);
    } else {
      q1 = s_tet*c_phi;
      q2 = s_tet*s_phi;
      q3 = c_tet;
    }
          
    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);
    
  }
}