G4DiffractiveSplitableHadron.cc

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// ------------------------------------------------------------
//      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;
  G4LorentzVector tmp=G4LorentzVector(0.,0.,0.,0.);
  Parton[0] = new G4Parton( 1 );
  Parton[1] = new G4Parton(-1 );

  Parton[0]->Set4Momentum(tmp); Parton[1]->Set4Momentum(tmp);
}


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

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() {}


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

void G4DiffractiveSplitableHadron::SplitUp() {

  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 );

  G4LorentzVector tmp=G4LorentzVector(0.,0.,0.,0.);
  Parton[0]->Set4Momentum(tmp); Parton[1]->Set4Momentum(tmp);

  /*                                        // Inversion of a string
  if ( G4UniformRand() < 1.75 ) {  //0.75
    Parton[0] = new G4Parton( stringStart );
    Parton[1] = new G4Parton( stringEnd );
  } else {
    Parton[0] = new G4Parton( stringEnd );
    Parton[1] = new G4Parton( stringStart );
  }
  */

  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 );
  G4LorentzVector tmp=G4LorentzVector(0.,0.,0.,0.);
  Parton[0]->Set4Momentum(tmp);
}


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

void G4DiffractiveSplitableHadron::SetSecondParton( G4int PDGcode ) {
  delete Parton[1];
  Parton[1] = new G4Parton( PDGcode );
  G4LorentzVector tmp=G4LorentzVector(0.,0.,0.,0.);
  Parton[1]->Set4Momentum(tmp);
}


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

void G4DiffractiveSplitableHadron::ChooseStringEnds( G4int PDGcode, G4int* aEnd,
                                                     G4int* bEnd ) const {
  G4int absPDGcode = std::abs( PDGcode );

  if ( absPDGcode < 1000 ) {  //--------------------  Meson -------------
    G4int heavy(0), light(0);
    if (!((absPDGcode == 111)||(absPDGcode == 221)||(absPDGcode == 331)))
    {                          // Ordinary mesons =======================
     heavy = absPDGcode/100;
     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;
    } 
    else 
    {                         // Pi0, Eta, Eta' =======================
     if ( G4UniformRand() < 0.5 ) {heavy = 1; light = -1;}
     else                         {heavy = 2; light = -2;}
    }
    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 SuppresUUDDSS=1.0/2.0;
    if ((j1000 == j100) && (j1000 == j10)) SuppresUUDDSS=1.; 

    const G4int maxNumberOfLoops = 1000;
    G4int loopCounter = 0;
    do
    {
      G4double random = G4UniformRand();

      if (random < 0.33333)
      {
        if (( j100 == j10 ) && ( G4UniformRand() > SuppresUUDDSS )) continue;
        *aEnd = j1000;
        if ( j100 == j10 )             {*bEnd = Diquark( j100, j10, 1 );}
        else
          if ( G4UniformRand() > 0.25) {*bEnd = Diquark( j100, j10, 0 );}
          else                        {*bEnd = Diquark( j100, j10, 1 );}
        break;
       }
       else if (random < 0.66667)
       {
        if (( j1000 == j10 ) && ( G4UniformRand() > SuppresUUDDSS )) continue;
        *aEnd = j100;
        if ( j1000 == j10 )            {*bEnd = Diquark( j1000, j10, 1 );}
        else
          if ( G4UniformRand() > 0.25) {*bEnd = Diquark( j1000, j10, 0 );}
          else                        {*bEnd = Diquark( j1000, j10, 1 );}
        break;
       }
       else
       {
        if (( j1000 == j100 ) && ( G4UniformRand() > SuppresUUDDSS )) continue;
        *aEnd = j10;
        if ( j1000 == j100 )           {*bEnd = Diquark( j1000, j100, 1 );}
        else
          if ( G4UniformRand() > 0.25) {*bEnd = Diquark( j1000, j100, 0 );}
          else                        {*bEnd = Diquark( j1000, j100, 1 );}
        break;
       }
    } while ( (true) && 
              ++loopCounter < maxNumberOfLoops );  /* Loop checking, 10.08.2015, A.Ribon */
    if ( loopCounter >= maxNumberOfLoops ) {
      *aEnd = j10; *bEnd = Diquark( j1000, j100, 1 );  // Just something acceptable, without any physics consideration.
    }

  }
}


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

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;
}