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);
        
    }
}