G4QGSMFragmentation.cc

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// $Id$
//
// -----------------------------------------------------------------------------
//      GEANT 4 class implementation file
//
//      History: first implementation, Maxim Komogorov, 10-Jul-1998
// -----------------------------------------------------------------------------
#include "G4QGSMFragmentation.hh"
#include "G4PhysicalConstants.hh"
#include "Randomize.hh"
#include "G4ios.hh"
#include "G4FragmentingString.hh"
#include "G4DiQuarks.hh"
#include "G4Quarks.hh"

// Class G4QGSMFragmentation 
//****************************************************************************************
 
G4QGSMFragmentation::G4QGSMFragmentation() :
arho(0.5), aphi(0.), an(-0.5), ala(-0.75), aksi(-1.), alft(0.5)
   {
   }

G4QGSMFragmentation::~G4QGSMFragmentation()
   {
   }

//----------------------------------------------------------------------------------------------------------

G4KineticTrackVector* G4QGSMFragmentation::FragmentString(const G4ExcitedString& theString)
{
//    Can no longer modify Parameters for Fragmentation.
        PastInitPhase=true;
        
//      check if string has enough mass to fragment...
        G4KineticTrackVector * LeftVector=LightFragmentationTest(&theString);
        if ( LeftVector != 0 ) return LeftVector;
        
        LeftVector = new G4KineticTrackVector;
        G4KineticTrackVector * RightVector=new G4KineticTrackVector;

// this should work but its only a semi deep copy. %GF  G4ExcitedString theStringInCMS(theString);
        G4ExcitedString *theStringInCMS=CPExcited(theString);
        G4LorentzRotation toCms=theStringInCMS->TransformToAlignedCms();

        G4bool success=false, inner_sucess=true;
        G4int attempt=0;
        while ( !success && attempt++ < StringLoopInterrupt )
        {
                G4FragmentingString *currentString=new G4FragmentingString(*theStringInCMS);

                std::for_each(LeftVector->begin(), LeftVector->end(), DeleteKineticTrack());
                LeftVector->clear();
                std::for_each(RightVector->begin(), RightVector->end(), DeleteKineticTrack());
                RightVector->clear();
                
                inner_sucess=true;  // set false on failure..
                while (! StopFragmenting(currentString) )
                {  // Split current string into hadron + new string
                        G4FragmentingString *newString=0;  // used as output from SplitUp...
                        G4KineticTrack * Hadron=Splitup(currentString,newString);
                        if ( Hadron != 0 && IsFragmentable(newString)) 
                        {
                           if ( currentString->GetDecayDirection() > 0 )
                                   LeftVector->push_back(Hadron);
                           else
                                   RightVector->push_back(Hadron);
                           delete currentString;
                           currentString=newString;
                        } else {
                         // abandon ... start from the beginning
                           if (newString) delete newString;          // Uzhi restore 20.06.08
                           if (Hadron)    delete Hadron;
                           inner_sucess=false;
                           break;
                        }
                } 
                // Split current string into 2 final Hadrons
                if ( inner_sucess && 
                     SplitLast(currentString,LeftVector, RightVector) ) 
                {
                        success=true;
                }
                delete currentString;
        }
        
        delete theStringInCMS;
        
        if ( ! success )
        {
                std::for_each(LeftVector->begin(), LeftVector->end(), DeleteKineticTrack());
                LeftVector->clear();
                std::for_each(RightVector->begin(), RightVector->end(), DeleteKineticTrack());
                delete RightVector;
                return LeftVector;
        }
                
        // Join Left- and RightVector into LeftVector in correct order.
        while(!RightVector->empty())
        {
            LeftVector->push_back(RightVector->back());
            RightVector->erase(RightVector->end()-1);
        }
        delete RightVector;

        CalculateHadronTimePosition(theString.Get4Momentum().mag(), LeftVector);

        G4LorentzRotation toObserverFrame(toCms.inverse());

        for(size_t C1 = 0; C1 < LeftVector->size(); C1++)
        {
           G4KineticTrack* Hadron = LeftVector->operator[](C1);
           G4LorentzVector Momentum = Hadron->Get4Momentum();
           Momentum = toObserverFrame*Momentum;
           Hadron->Set4Momentum(Momentum);
           G4LorentzVector Coordinate(Hadron->GetPosition(), Hadron->GetFormationTime());
           Momentum = toObserverFrame*Coordinate;
           Hadron->SetFormationTime(Momentum.e());
           G4ThreeVector aPosition(Momentum.vect());
           Hadron->SetPosition(theString.GetPosition()+aPosition);
        }
        return LeftVector;
                


}

//----------------------------------------------------------------------------------------------------------

G4double G4QGSMFragmentation::GetLightConeZ(G4double zmin, G4double zmax, G4int PartonEncoding,  G4ParticleDefinition* , G4double , G4double )
{    
  G4double z;    
  G4double theA(0), d1, d2, yf;
  G4int absCode = std::abs( PartonEncoding );
  if (absCode < 10)
  { 
    if(absCode == 1 || absCode == 2) theA = arho;
    else if(absCode == 3) theA = aphi;
    else throw G4HadronicException(__FILE__, __LINE__, "Unknown PDGencoding in G4QGSMFragmentation::G4LightConeZ");

    do  
    {
      z  = zmin + G4UniformRand() * (zmax - zmin);
      d1 =  (1. - z);
      d2 =  (alft - theA);
      yf = std::pow(d1, d2);
    } 
    while (G4UniformRand() > yf);
  }
  else
  {       
    if(absCode == 1103 || absCode == 2101 || 
       absCode == 2203 || absCode == 2103)
    {
      d2 =  (alft - (2.*an - arho));
    }
    else if(absCode == 3101 || absCode == 3103 ||
            absCode == 3201 || absCode == 3203)
    {
      d2 =  (alft - (2.*ala - arho));
    }
    else
    {
      d2 =  (alft - (2.*aksi - arho));
    }

    do  
    {
      z = zmin + G4UniformRand() * (zmax - zmin);
      d1 =  (1. - z);
      yf = std::pow(d1, d2);
    } 
    while (G4UniformRand() > yf); 
  }
  return z;
}
//-----------------------------------------------------------------------------------------

G4LorentzVector * G4QGSMFragmentation::SplitEandP(G4ParticleDefinition * pHadron,
                                                  G4FragmentingString * string,    // Uzhi
                                                  G4FragmentingString * ) // Uzhi
{
       G4double HadronMass = pHadron->GetPDGMass();

       // calculate and assign hadron transverse momentum component HadronPx andHadronPy
       G4ThreeVector thePt;
       thePt=SampleQuarkPt();
       G4ThreeVector HadronPt = thePt +string->DecayPt();
       HadronPt.setZ(0);
       //...  sample z to define hadron longitudinal momentum and energy
       //... but first check the available phase space
       G4double DecayQuarkMass2  = sqr(string->GetDecayParton()->GetPDGMass());
       G4double HadronMass2T = sqr(HadronMass) + HadronPt.mag2();
       if (DecayQuarkMass2 + HadronMass2T >= SmoothParam*(string->Mass2()) ) 
          return 0;             // have to start all over!

       //... then compute allowed z region  z_min <= z <= z_max 
 
       G4double zMin = HadronMass2T/(string->Mass2());
       G4double zMax = 1. - DecayQuarkMass2/(string->Mass2());
       if (zMin >= zMax) return 0;              // have to start all over!
        
       G4double z = GetLightConeZ(zMin, zMax,
                       string->GetDecayParton()->GetPDGEncoding(), pHadron,
                       HadronPt.x(), HadronPt.y());      
       
       //... now compute hadron longitudinal momentum and energy
       // longitudinal hadron momentum component HadronPz

        HadronPt.setZ(0.5* string->GetDecayDirection() *
                        (z * string->LightConeDecay() - 
                         HadronMass2T/(z * string->LightConeDecay())));
        G4double HadronE  = 0.5* (z * string->LightConeDecay() + 
                                  HadronMass2T/(z * string->LightConeDecay()));

       G4LorentzVector * a4Momentum= new G4LorentzVector(HadronPt,HadronE);

       return a4Momentum;
}


//-----------------------------------------------------------------------------------------

G4bool G4QGSMFragmentation::SplitLast(G4FragmentingString * string,
                                             G4KineticTrackVector * LeftVector,
                                             G4KineticTrackVector * RightVector)
{
    //... perform last cluster decay
    G4ThreeVector ClusterVel =string->Get4Momentum().boostVector();
    G4double ResidualMass    =string->Mass(); 
    G4double ClusterMassCut = ClusterMass;
    G4int cClusterInterrupt = 0;
    G4ParticleDefinition * LeftHadron, * RightHadron;
    do
    {
        if (cClusterInterrupt++ >= ClusterLoopInterrupt)
        {
          return false;
        }
        G4ParticleDefinition * quark = NULL;
        string->SetLeftPartonStable(); // to query quark contents..
        if (string->DecayIsQuark() && string->StableIsQuark() ) 
        {
           //... there are quarks on cluster ends
                LeftHadron= QuarkSplitup(string->GetLeftParton(), quark);
        } else {
           //... there is a Diquark on cluster ends
                G4int IsParticle;
                if ( string->StableIsQuark() ) {
                  IsParticle=(string->GetLeftParton()->GetPDGEncoding()>0) ? -1 : +1; 
                } else {
                  IsParticle=(string->GetLeftParton()->GetPDGEncoding()>0) ? +1 : -1;
                }
                pDefPair QuarkPair = CreatePartonPair(IsParticle,false);  // no diquarks wanted
                quark = QuarkPair.second;
                LeftHadron=hadronizer->Build(QuarkPair.first, string->GetLeftParton());
        }
        RightHadron = hadronizer->Build(string->GetRightParton(), quark);

       //... repeat procedure, if mass of cluster is too low to produce hadrons
       //... ClusterMassCut = 0.15*GeV model parameter
        if ( quark->GetParticleSubType()== "quark" ) {ClusterMassCut = 0.;}
        else {ClusterMassCut = ClusterMass;}
    } 
    while (ResidualMass <= LeftHadron->GetPDGMass() + RightHadron->GetPDGMass()  + ClusterMassCut);

    //... compute hadron momenta and energies   
    G4LorentzVector  LeftMom, RightMom;
    G4ThreeVector    Pos;
    Sample4Momentum(&LeftMom, LeftHadron->GetPDGMass(), &RightMom, RightHadron->GetPDGMass(), ResidualMass);
    LeftMom.boost(ClusterVel);
    RightMom.boost(ClusterVel);
    LeftVector->push_back(new G4KineticTrack(LeftHadron, 0, Pos, LeftMom));
    RightVector->push_back(new G4KineticTrack(RightHadron, 0, Pos, RightMom));

    return true;

}

//----------------------------------------------------------------------------------------------------------

G4bool G4QGSMFragmentation::IsFragmentable(const G4FragmentingString * const string)
{
        return sqr(FragmentationMass(string)+MassCut) <
                        string->Mass2();
}

//----------------------------------------------------------------------------------------------------------

G4bool G4QGSMFragmentation::StopFragmenting(const G4FragmentingString * const string)
{
        return
         sqr(FragmentationMass(string,&G4HadronBuilder::BuildHighSpin)+MassCut) >
         string->Get4Momentum().mag2();
}

//----------------------------------------------------------------------------------------------------------

//----------------------------------------------------------------------------------------------------------

void G4QGSMFragmentation::Sample4Momentum(G4LorentzVector* Mom, G4double Mass, G4LorentzVector* AntiMom, G4double AntiMass, G4double InitialMass) 
    {
    G4double r_val = sqr(InitialMass*InitialMass - Mass*Mass - AntiMass*AntiMass) - sqr(2.*Mass*AntiMass);
    G4double Pabs = (r_val > 0.)? std::sqrt(r_val)/(2.*InitialMass) : 0;

    //... sample unit vector       
    G4double pz = 1. - 2.*G4UniformRand();  
    G4double st     = std::sqrt(1. - pz * pz)*Pabs;
    G4double phi    = 2.*pi*G4UniformRand();
    G4double px = st*std::cos(phi);
    G4double py = st*std::sin(phi);
    pz *= Pabs;
    
    Mom->setPx(px); Mom->setPy(py); Mom->setPz(pz);
    Mom->setE(std::sqrt(Pabs*Pabs + Mass*Mass));

    AntiMom->setPx(-px); AntiMom->setPy(-py); AntiMom->setPz(-pz);
    AntiMom->setE (std::sqrt(Pabs*Pabs + AntiMass*AntiMass));
    }

    
//*********************************************************************************************

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