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// $Id: G4Parton.cc,v 1.13 2002/12/12 19:17:58 gunter Exp $
// GEANT4 tag $Name: geant4-05-02 $
//
// ------------------------------------------------------------
//      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"

G4Parton::G4Parton(G4int PDGcode)
{
	PDGencoding=PDGcode;
	theX = 0;
	theDefinition=G4ParticleTable::GetParticleTable()->FindParticle(PDGencoding);
	if (theDefinition == NULL)
	{
	  G4cout << "Encoding = "<<PDGencoding<<G4endl;
	  G4Exception("G4Parton::GetDefinition(): Encoding not in particle table");
	}
	//
	// 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)*(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)*(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;
	  G4Exception("G4Parton::GetDefinition(): Particle is not a parton");
	}
	//  
	// 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;
}

const G4Parton & G4Parton::operator=(const G4Parton &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);
}