G4DiffractiveSplitableHadron.cc

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// $Id: G4DiffractiveSplitableHadron.cc 74627 2013-10-17 07:04:38Z gcosmo $
// GEANT4 tag $Name:  $
//

// ------------------------------------------------------------
//      GEANT 4 class implementation file
//
//      ---------------- G4DiffractiveSplitableHadron----------------
//             by Gunter Folger, August 1998.
//       class splitting an interacting particle. Used by FTF String Model.
// ------------------------------------------------------------

#include "G4DiffractiveSplitableHadron.hh"

#include "G4ParticleDefinition.hh"
#include "Randomize.hh"


//============================================================================

G4DiffractiveSplitableHadron::G4DiffractiveSplitableHadron() {
  PartonIndex = -1;
  Parton[0] = new G4Parton( 1 );
  Parton[1] = new G4Parton(-1 );
}


//============================================================================

G4DiffractiveSplitableHadron::G4DiffractiveSplitableHadron( const G4ReactionProduct& aPrimary ) :
  G4VSplitableHadron( aPrimary )
{
  PartonIndex = -2;
  Parton[0] = NULL;
}


//============================================================================

G4DiffractiveSplitableHadron::G4DiffractiveSplitableHadron( const G4Nucleon& aNucleon ) :
  G4VSplitableHadron( aNucleon )
{
  PartonIndex = -2;
  Parton[0] = NULL;
}


//============================================================================

G4DiffractiveSplitableHadron::G4DiffractiveSplitableHadron( const G4VKineticNucleon* aNucleon ) :
  G4VSplitableHadron( aNucleon )
{
  PartonIndex = -2;
  Parton[0] = NULL;
}


//============================================================================

G4DiffractiveSplitableHadron::~G4DiffractiveSplitableHadron() {
  //G4cout << "Destruct G4DiffractiveSplitableHadron" << Parton[0] << " " << Parton[1] << G4endl;
  //if ( Parton[0] != NULL ) { delete Parton[0]; delete Parton[1]; }
}


//============================================================================

void G4DiffractiveSplitableHadron::SplitUp() {
  //G4cout << "SplitUp() IsSplit() Parton[0] " << IsSplit() << " " << Parton[0] << G4endl;
  if ( IsSplit() ) return;
  Splitting();
  // Split once only...
  if ( Parton[0] != NULL ) return;

  // flavours of quark ends
  G4int PDGcode = GetDefinition()->GetPDGEncoding();
  G4int stringStart, stringEnd;
  ChooseStringEnds( PDGcode, &stringStart, &stringEnd );

  Parton[0] = new G4Parton( stringStart );
  Parton[1] = new G4Parton( stringEnd );
  PartonIndex = -1;
}


//============================================================================

G4Parton* G4DiffractiveSplitableHadron::GetNextParton() {
  ++PartonIndex;
  if ( PartonIndex > 1  ||  PartonIndex < 0 ) return NULL;
  G4int PartonInd( PartonIndex );
  if ( PartonIndex == 1 ) PartonIndex = -1;
  return Parton[ PartonInd ];
}


//============================================================================

G4Parton* G4DiffractiveSplitableHadron::GetNextAntiParton() {
  ++PartonIndex;
  if ( PartonIndex > 1  ||  PartonIndex < 0 ) return NULL;
  G4int PartonInd( PartonIndex );
  if ( PartonIndex == 1 ) PartonIndex = -1;
  return Parton[ PartonInd ];
}


//============================================================================

void G4DiffractiveSplitableHadron::SetFirstParton( G4int PDGcode ) {
  delete Parton[0];
  Parton[0] = new G4Parton( PDGcode );
}


//============================================================================

void G4DiffractiveSplitableHadron::SetSecondParton( G4int PDGcode ) {
  delete Parton[1];
  Parton[1] = new G4Parton( PDGcode );
}


//============================================================================

void G4DiffractiveSplitableHadron::ChooseStringEnds( G4int PDGcode, G4int* aEnd,
                                                     G4int* bEnd ) const {
  const G4double udspin1 = 1.0/6.0;
  const G4double uuspin1 = 1.0/3.0;
  //const G4double udspin0 = 1.0/2.0;

  G4int absPDGcode = std::abs( PDGcode );

  if ( absPDGcode < 1000 ) {  //--------------------  Meson -------------
    G4int heavy = absPDGcode/100;
    G4int light = (absPDGcode % 100)/10;
    //G4int anti = std::pow( -1 , std::max( heavy, light ) );
    G4int anti = 1 - 2*( std::max( heavy, light ) % 2 );
    if (PDGcode < 0 ) anti *= -1;
    heavy *= anti;
    light *= -1 * anti;
    if ( G4UniformRand() < 0.5 ) {
      *aEnd = heavy;
      *bEnd = light;
    } else {
      *aEnd = light;
      *bEnd = heavy;
    }
  } else {                    //-------------------- Baryon --------------
    G4int j1000 = PDGcode/1000;
    G4int j100  = (PDGcode % 1000)/100;
    G4int j10   = (PDGcode % 100)/10;
    G4double random = G4UniformRand();
    if ( std::abs( j100 ) >= std::abs( j10 ) ) {
      if ( random < udspin1 ) {
        *aEnd = j1000;
        *bEnd = Diquark( j100, j10, 1 );
      } else if ( random < udspin1 + uuspin1 ) {
        *aEnd = j10;
        *bEnd = Diquark( j1000, j100, 1 );
      } else {
        *aEnd = j100;
        // Careful, there is no diquark q1=q2, (q1 q2)0, possible for Omega-
        *bEnd = Diquark( j1000, j10, j1000 != j100 ? 0 : 1 );
      }
    } else {
      // Lambda-like hadrons have two lightest quarks in spin 0
      if ( random < udspin1 ) {
        *aEnd = j1000;
        // as above, but with charmed baryons
        *bEnd = Diquark( j100, j10, j100 != j10 ? 0 : 10 );
      } else if ( random < udspin1 + uuspin1 ) {
        *aEnd = j10;
        *bEnd = Diquark( j1000, j100, 1 );
      } else {
        *aEnd = j100;
        *bEnd = Diquark( j1000, j10, 1 );
      }
    }
  }

}


//============================================================================

G4int G4DiffractiveSplitableHadron::Diquark( G4int aquark, G4int bquark, G4int Spin) const {
  G4int diquarkPDG = std::max( std::abs( aquark ), std::abs( bquark ) ) * 1000 +
                     std::min( std::abs( aquark ), std::abs( bquark ) ) * 100  +
                     2*Spin + 1;
  return ( aquark > 0  &&  bquark > 0 ) ? diquarkPDG : -1*diquarkPDG;
}