G4Parton.cc

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//
//
//
// ------------------------------------------------------------
//      GEANT 4 class implementation file
//
//      ---------------- G4Parton ----------------
//             by Gunter Folger, June 1998.
//       class for Parton (inside a string) used by Parton String Models
// ------------------------------------------------------------

#include "G4Parton.hh"
#include "G4HadronicException.hh"

G4Parton::G4Parton(G4int PDGcode)
{
  PDGencoding=PDGcode;
  theX = 0;
  theDefinition=G4ParticleTable::GetParticleTable()->FindParticle(PDGencoding);
  if (theDefinition == NULL)
  {
    G4cout << "Encoding = "<<PDGencoding<<G4endl;
    G4String text = "G4Parton::GetDefinition(): Encoding not in particle table";
    throw G4HadronicException(__FILE__, __LINE__, text);
  }
  //
  // colour by random in (1,2,3)=(R,G,B) for quarks and 
  //                  in (-1,-2,-3)=(Rbar,Gbar,Bbar) for anti-quarks:
  //
  if (theDefinition->GetParticleType() == "quarks") {
    theColour = ((G4int)(3.*G4UniformRand())+1)*(std::abs(PDGencoding)/PDGencoding) ;
  }
  //
  // colour by random in (-1,-2,-3)=(Rbar,Gbar,Bbar)=(GB,RB,RG) for di-quarks and
  //                  in (1,2,3)=(R,G,B)=(GB,RB,RG) for anti-di-quarks:
  //
  else if (theDefinition->GetParticleType() == "diquarks") {
    theColour = -((G4int)(3.*G4UniformRand())+1)*(std::abs(PDGencoding)/PDGencoding);
  }
  //
  // colour by random in (-11,-12,...,-33)=(RRbar,RGbar,RBbar,...,BBbar) for gluons:
  //
  else if (theDefinition->GetParticleType() == "gluons") {
    theColour = -(((G4int)(3.*G4UniformRand())+1)*10 + ((G4int)(3.*G4UniformRand())+1));
  }
  else {
    G4cout << "Encoding = "<<PDGencoding<<G4endl;
    G4String text = "G4Parton::GetDefinition(): Particle is not a parton";
    throw G4HadronicException(__FILE__, __LINE__, text);
  }
  //  
  // isospin-z from PDG-encoded isospin-z for 
  // quarks, anti-quarks, di-quarks, and anti-di-quarks:
  //
  if ((theDefinition->GetParticleType() == "quarks") || (theDefinition->GetParticleType() == "diquarks")){
    theIsoSpinZ = theDefinition->GetPDGIsospin3();
  }
  //
  // isospin-z choosen at random from PDG-encoded isospin for gluons (should be zero):
  //
  else {
    G4int thisPDGiIsospin=theDefinition->GetPDGiIsospin();
    if (thisPDGiIsospin == 0) {
      theIsoSpinZ = 0;
    }
    else {
      theIsoSpinZ = ((G4int)((thisPDGiIsospin+1)*G4UniformRand()))-thisPDGiIsospin*0.5;
    }
  }
  //
  // spin-z choosen at random from PDG-encoded spin:
  //
  G4int thisPDGiSpin=theDefinition->GetPDGiSpin();
  if (thisPDGiSpin == 0) {
    theSpinZ = 0;
  }
  else {
    G4int rand=((G4int)((thisPDGiSpin+1)*G4UniformRand()));
    theSpinZ = rand-thisPDGiSpin*0.5;;
  }
}

G4Parton::G4Parton(const G4Parton &right)
{
  PDGencoding = right.PDGencoding;
  theMomentum = right.theMomentum;
  thePosition = right.thePosition;
  theX = right.theX;
  theDefinition = right.theDefinition;
  theColour = right.theColour;
  theIsoSpinZ = right.theIsoSpinZ;
  theSpinZ = right.theSpinZ;
}

G4Parton & G4Parton::operator=(const G4Parton &right)
{
   if (this != &right)
   {
      PDGencoding=right.GetPDGcode();
      theMomentum=right.Get4Momentum();
      thePosition=right.GetPosition();
      theX = right.theX;
      theDefinition = right.theDefinition;
      theColour = right.theColour;
      theIsoSpinZ = right.theIsoSpinZ;
      theSpinZ = right.theSpinZ;
   }

  return *this;
}

G4Parton::~G4Parton()
{
//  cout << "G4Parton::~G4Parton(): this = "<<this <<endl;
//  cout << "break here"<<this <<endl;
}

void G4Parton::DefineMomentumInZ(G4double aLightConeMomentum, G4bool aDirection)
{
  G4double Mass = GetMass();
  G4LorentzVector a4Momentum = Get4Momentum();
  aLightConeMomentum*=theX;
  G4double TransverseMass2 = sqr(a4Momentum.px()) + sqr(a4Momentum.py()) + sqr(Mass);
  a4Momentum.setPz(0.5*(aLightConeMomentum - TransverseMass2/aLightConeMomentum)*(aDirection? 1: -1)); 
  a4Momentum.setE( 0.5*(aLightConeMomentum + TransverseMass2/aLightConeMomentum));
  Set4Momentum(a4Momentum);
}  

void G4Parton::DefineMomentumInZ(G4double aLightConeMomentum,G4double aLightConeE, G4bool aDirection)
{
  G4double Mass = GetMass();
  G4LorentzVector a4Momentum = Get4Momentum();
  aLightConeMomentum*=theX;
  aLightConeE*=theX;
  G4double TransverseMass2 = sqr(a4Momentum.px()) + sqr(a4Momentum.py()) + sqr(Mass);
  a4Momentum.setPz(0.5*(aLightConeMomentum - aLightConeE - TransverseMass2/aLightConeMomentum)*(aDirection? 1: -1)); 
  a4Momentum.setE( 0.5*(aLightConeMomentum + aLightConeE + TransverseMass2/aLightConeMomentum));
  Set4Momentum(a4Momentum);
}