G4INCLStrangeAbsorbtionChannel.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 "G4INCLStrangeAbsorbtionChannel.hh"
#include "G4INCLKinematicsUtils.hh"
#include "G4INCLBinaryCollisionAvatar.hh"
#include "G4INCLRandom.hh"
#include "G4INCLGlobals.hh"
#include "G4INCLLogger.hh"
 
namespace G4INCL {
 
  StrangeAbsorbtionChannel::StrangeAbsorbtionChannel(Particle *p1, Particle *p2)
    : particle1(p1), particle2(p2)
  {
 
  }
 
  StrangeAbsorbtionChannel::~StrangeAbsorbtionChannel(){}
  
  void StrangeAbsorbtionChannel::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 StrangeAbsorbtionChannel::fillFinalState(FinalState *fs) {
    Particle * nucleon;
    Particle * strange;
    
    ThreeVector const incidentDirection = particle1->getMomentum() + particle2->getMomentum();
    
    if(particle1->isNucleon()) {
      nucleon = particle1;
      strange = particle2;
    } else {
      nucleon = particle2;
      strange = particle1;
    }
// assert(strange->isSigma() || strange->isAntiKaon());
 
    ParticleType finalType = Neutron;
    if(ParticleConfig::isPair(nucleon, strange, Neutron, KZeroBar)) {
      finalType = PiZero;
    } else if(ParticleConfig::isPair(nucleon, strange, Proton, KZeroBar)) {
      finalType = PiPlus;
    } else if(ParticleConfig::isPair(nucleon, strange, Neutron, KMinus)) {
      finalType = PiMinus;
    } else if(ParticleConfig::isPair(nucleon, strange, Proton, KMinus)) {
      finalType = PiZero;
    } else if(ParticleConfig::isPair(nucleon, strange, Proton, SigmaMinus)) {
      finalType = Neutron;
    } else if(ParticleConfig::isPair(nucleon, strange, Neutron, SigmaZero)) {
      finalType = Neutron;
    } else if(ParticleConfig::isPair(nucleon, strange, Proton, SigmaZero)) {
      finalType = Proton;
    } else if(ParticleConfig::isPair(nucleon, strange, Neutron, SigmaPlus)) {
      finalType = Proton;
    } else {
      INCL_ERROR("Unknown particle pair in Strange-N absorption: " << nucleon << '\t' << strange << '\n');
      return;
    }
 
    G4double energycm = KinematicsUtils::totalEnergyInCM(nucleon, strange);
    
    G4double finalTypemass = ParticleTable::getINCLMass(finalType);
    nucleon->setType(Lambda); // nucleon becomes the lambda
    G4double lambdamass = nucleon->getMass();
    
    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(energycm,
                                              lambdamass,
                                              finalTypemass);
    
    q1 *= xq;
    q2 *= xq;
    q3 *= xq;
    
    ThreeVector finalMomentum(q1, q2, q3);
    
    strange->setType(finalType);
    strange->setMomentum(finalMomentum);
    strange->adjustEnergyFromMomentum();
    nucleon->setMomentum(-finalMomentum);
    nucleon->adjustEnergyFromMomentum();
 
    fs->addModifiedParticle(nucleon); // nucleon became a lambda
    fs->addModifiedParticle(strange);  // the strange particle became an unstange particle
  }
 
}