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));
    }
 
    
//*********************************************************************************************