G4INCLParticleEntryChannel.cc

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

#include "globals.hh"

#include "G4INCLParticleEntryChannel.hh"
#include "G4INCLRootFinder.hh"
#include "G4INCLIntersection.hh"
#include <algorithm>

namespace G4INCL {

  ParticleEntryChannel::ParticleEntryChannel(Nucleus *n, Particle *p)
    :theNucleus(n), theParticle(p)
  {}

  ParticleEntryChannel::~ParticleEntryChannel()
  {}

  FinalState* ParticleEntryChannel::getFinalState() {
    // Behaves slightly differency if a third body (the projectile) is present
    G4bool isNN = theNucleus->isNucleusNucleusCollision();

    /* Corrections to the energy of the entering nucleon
     *
     * In particle-nucleus reactions, the goal of this correction is to satisfy
     * energy conservation in particle-nucleus reactions using real particle
     * and nuclear masses.
     *
     * In nucleus-nucleus reactions, in addition to the above, the correction
     * is determined by a model for the excitation energy of the
     * quasi-projectile (QP). The energy of the entering nucleon is such that
     * the QP excitation energy, as determined by conservation, is what given
     * by our model.
     *
     * Possible choices for the correction (or, equivalently, for the QP excitation energy):
     * 1. the correction is 0. (same as in particle-nucleus);
     * 2. the correction is the separation energy of the entering nucleon in
     *    the current QP;
     * 3. the QP excitation energy is given by A. Boudard's algorithm, as
     *    implemented in INCL4.2-HI/Geant4.
     *
     * Ideally, the QP excitation energy should always be >=0. Algorithms 1.
     * and 2. do not guarantee this, although violations to the rule seem to be
     * more severe for 1. than for 2.. Algorithm 3., by construction, yields
     * non-negative QP excitation energies.
     */
    G4double theCorrection;
    if(isNN) {
// assert(theParticle->isNucleon());
      ProjectileRemnant * const projectileRemnant = theNucleus->getProjectileRemnant();
// assert(projectileRemnant);

      // No correction (model 1. above)
      /*
      theCorrection = theParticle->getEmissionQValueCorrection(
          theNucleus->getA() + theParticle->getA(),
          theNucleus->getZ() + theParticle->getZ())
        + theParticle->getTableMass() - theParticle->getINCLMass();
      const G4double theProjectileCorrection = 0.;
      */

      // Correct the energy of the entering particle for the Q-value of the
      // emission from the projectile (model 2. above)
      /*
      theCorrection = theParticle->getTransferQValueCorrection(
          projectileRemnant->getA(), projectileRemnant->getZ(),
          theNucleus->getA(), theNucleus->getZ());
      G4double theProjectileCorrection;
      if(projectileRemnant->getA()>theParticle->getA()) { // if there are any particles left
        // Compute the projectile Q-value (to be used as a correction to the
        // other components of the projectile remnant)
        theProjectileCorrection = ParticleTable::getTableQValue(
            projectileRemnant->getA() - theParticle->getA(),
            projectileRemnant->getZ() - theParticle->getZ(),
            theParticle->getA(),
            theParticle->getZ());
      } else
        theProjectileCorrection = 0.;
      */

      // Fix the correction in such a way that the quasi-projectile excitation
      // energy is given by A. Boudard's INCL4.2-HI model.
      const G4double theProjectileExcitationEnergy =
       (projectileRemnant->getA()-theParticle->getA()>1) ?
       (projectileRemnant->computeExcitationEnergy(theParticle->getID())) :
       0.;
      const G4double theProjectileEffectiveMass =
        ParticleTable::getTableMass(projectileRemnant->getA() - theParticle->getA(), projectileRemnant->getZ() - theParticle->getZ())
        + theProjectileExcitationEnergy;
      const ThreeVector &theProjectileMomentum = projectileRemnant->getMomentum() - theParticle->getMomentum();
      const G4double theProjectileEnergy = std::sqrt(theProjectileMomentum.mag2() + theProjectileEffectiveMass*theProjectileEffectiveMass);
      const G4double theProjectileCorrection = theProjectileEnergy - (projectileRemnant->getEnergy() - theParticle->getEnergy());
      theCorrection = theParticle->getEmissionQValueCorrection(
          theNucleus->getA() + theParticle->getA(),
          theNucleus->getZ() + theParticle->getZ())
        + theParticle->getTableMass() - theParticle->getINCLMass()
        + theProjectileCorrection;

      projectileRemnant->removeParticle(theParticle, theProjectileCorrection);
    } else {
      const G4int ACN = theNucleus->getA() + theParticle->getA();
      const G4int ZCN = theNucleus->getZ() + theParticle->getZ();
      // Correction to the Q-value of the entering particle
      theCorrection = theParticle->getEmissionQValueCorrection(ACN,ZCN);
      DEBUG("The following Particle enters with correction " << theCorrection
          << theParticle->print() << std::endl);
    }

    const G4double energyBefore = theParticle->getEnergy() - theCorrection;
    G4bool success = particleEnters(theCorrection);
    FinalState *fs = new FinalState();
    fs->addEnteringParticle(theParticle);

    if(!success) {
      fs->makeParticleBelowZero();
    } else if(theParticle->isNucleon() &&
        theParticle->getKineticEnergy()<theNucleus->getPotential()->getFermiEnergy(theParticle)) {
      // If the participant is a nucleon entering below its Fermi energy, force a
      // compound nucleus
      fs->makeParticleBelowFermi();
    }

    fs->setTotalEnergyBeforeInteraction(energyBefore);
    return fs;
  }

  G4bool ParticleEntryChannel::particleEnters(const G4double theQValueCorrection) {

    // \todo{this is the place to add refraction}

    theParticle->setINCLMass(); // Will automatically put the particle on shell

    // Add the nuclear potential to the kinetic energy when entering the
    // nucleus

    class IncomingEFunctor : public RootFunctor {
      public:
        IncomingEFunctor(Particle * const p, Nucleus const * const n, const G4double correction) :
          RootFunctor(0., 1E6),
          theParticle(p),
          thePotential(n->getPotential()),
          theEnergy(theParticle->getEnergy()),
          theMass(theParticle->getMass()),
          theQValueCorrection(correction),
          theMomentum(theParticle->getMomentum())
          {}
        ~IncomingEFunctor() {}
        G4double operator()(const G4double v) const {
          G4double energyInside = std::max(theMass, theEnergy + v - theQValueCorrection);
          theParticle->setEnergy(energyInside);
          theParticle->setPotentialEnergy(v);
          // Scale the particle momentum
          theParticle->setMomentum(theMomentum); // keep the same direction
          theParticle->adjustMomentumFromEnergy();
          return v - thePotential->computePotentialEnergy(theParticle);
        }
        void cleanUp(const G4bool /*success*/) const {}
      private:
        Particle *theParticle;
        NuclearPotential::INuclearPotential const *thePotential;
        G4double theEnergy;
        G4double theMass;
        G4double theQValueCorrection;
        ThreeVector theMomentum;
    } theIncomingEFunctor(theParticle,theNucleus,theQValueCorrection);

    G4double v = theNucleus->getPotential()->computePotentialEnergy(theParticle);
    if(theParticle->getKineticEnergy()+v-theQValueCorrection<0.) { // Particle entering below 0. Die gracefully
      DEBUG("Particle " << theParticle->getID() << " is trying to enter below 0" << std::endl);
      return false;
    }
    G4bool success = RootFinder::solve(&theIncomingEFunctor, v);
    if(success) { // Apply the solution
      std::pair<G4double,G4double> theSolution = RootFinder::getSolution();
      theIncomingEFunctor(theSolution.first);
    } else {
      WARN("Couldn't compute the potential for incoming particle, root-finding algorithm failed." << std::endl);
    }
    return success;
  }

}