G4HadronBuilder.cc

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// $Id$
//
// -----------------------------------------------------------------------------
//      GEANT 4 class implementation file
//
//      History: 
//             Gunter Folger, August/September 2001
//               Create class; algorithm previously in G4VLongitudinalStringDecay.
// -----------------------------------------------------------------------------

#include "G4HadronBuilder.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"
#include "G4HadronicException.hh"
#include "G4ParticleTable.hh"

G4HadronBuilder::G4HadronBuilder(G4double mesonMix, G4double barionMix,
                     std::vector<double> scalarMesonMix,
                     std::vector<double> vectorMesonMix)
{
        mesonSpinMix=mesonMix;       
        barionSpinMix=barionMix;
        scalarMesonMixings=scalarMesonMix;
        vectorMesonMixings=vectorMesonMix;
}

G4ParticleDefinition * G4HadronBuilder::Build(G4ParticleDefinition * black, G4ParticleDefinition * white)
{

        if (black->GetParticleSubType()== "di_quark" || white->GetParticleSubType()== "di_quark" ) {

//    Barion
           Spin spin = (G4UniformRand() < barionSpinMix) ? SpinHalf : SpinThreeHalf;
           return Barion(black,white,spin);

        } else {        

//    Meson
           Spin spin = (G4UniformRand() < mesonSpinMix) ? SpinZero : SpinOne;
           return Meson(black,white,spin);

        }
}

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

G4ParticleDefinition * G4HadronBuilder::BuildLowSpin(G4ParticleDefinition * black, G4ParticleDefinition * white)
{
        if ( black->GetParticleSubType()== "quark" && white->GetParticleSubType()== "quark" ) {
                return Meson(black,white, SpinZero);
        } else {
//                    will return a SpinThreeHalf Barion if all quarks the same
                return Barion(black,white, SpinHalf); 
        }       
}

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

G4ParticleDefinition * G4HadronBuilder::BuildHighSpin(G4ParticleDefinition * black, G4ParticleDefinition * white)
{
        if ( black->GetParticleSubType()== "quark" && white->GetParticleSubType()== "quark" ) {
                return Meson(black,white, SpinOne);
        } else {
                return Barion(black,white,SpinThreeHalf);
        }
}

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

G4ParticleDefinition * G4HadronBuilder::Meson(G4ParticleDefinition * black, 
                                              G4ParticleDefinition * white, Spin theSpin)
{
#ifdef G4VERBOSE
//  Verify Input Charge
   
   G4double charge =  black->GetPDGCharge() 
                    + white->GetPDGCharge();     
   if (std::abs(charge) > 2 || std::abs(3.*charge - 3*G4int(charge*1.001)) > perCent )   // 1.001 to avoid int(.9999) -> 0
        {
            G4cerr << " G4HadronBuilder::Build()" << G4endl;
            G4cerr << "    Invalid total charge found for on input: " 
                        << charge<< G4endl;
            G4cerr << "    PGDcode input quark1/quark2 : " <<
                        black->GetPDGEncoding() << " / "<< 
                        white->GetPDGEncoding() << G4endl;
            G4cerr << G4endl;
        } 
#endif  
        
        G4int id1= black->GetPDGEncoding();
        G4int id2= white->GetPDGEncoding();
//      G4int ifl1= std::max(std::abs(id1), std::abs(id2));
        if ( std::abs(id1) < std::abs(id2) )
           {
           G4int xchg = id1; 
           id1 = id2;  
           id2 = xchg;
           }
        
        if (std::abs(id1) > 3 ) 
           throw G4HadronicException(__FILE__, __LINE__, "G4HadronBuilder::Meson : Illegal Quark content as input");
        
        G4int PDGEncoding=0;

        if (id1 + id2 == 0) {     
           G4double rmix = G4UniformRand();
           G4int    imix = 2*std::abs(id1) - 1;
           if(theSpin == SpinZero) {
              PDGEncoding = 110*(1 + (G4int)(rmix + scalarMesonMixings[imix - 1])
                                   + (G4int)(rmix + scalarMesonMixings[imix])
                                ) +  theSpin;
           } else {
              PDGEncoding = 110*(1 + (G4int)(rmix + vectorMesonMixings[imix - 1])
                                   + (G4int)(rmix + vectorMesonMixings[imix])
                                ) +  theSpin;
           }
        } else {
           PDGEncoding = 100 * std::abs(id1) + 10 * std::abs(id2) +  theSpin;  
           G4bool IsUp = (std::abs(id1)&1) == 0;        // quark 1 up type quark (u or c)
           G4bool IsAnti = id1 < 0;             // quark 1 is antiquark?
           if( (IsUp && IsAnti ) || (!IsUp && !IsAnti ) ) 
              PDGEncoding = - PDGEncoding;
        }
           
           
        G4ParticleDefinition * MesonDef=
                G4ParticleTable::GetParticleTable()->FindParticle(PDGEncoding);
#ifdef G4VERBOSE
        if (MesonDef == 0 ) {
                G4cerr << " G4HadronBuilder - Warning: No particle for PDGcode= "
                       << PDGEncoding << G4endl;
        } else if  ( (  black->GetPDGCharge() + white->GetPDGCharge()
                        - MesonDef->GetPDGCharge() ) > perCent   ) {
                G4cerr << " G4HadronBuilder - Warning: Incorrect Charge : "
                        << " Quark1/2 = " 
                        << black->GetParticleName() << " / "
                        << white->GetParticleName() 
                        << " resulting Hadron " << MesonDef->GetParticleName() 
                        << G4endl;
        }
#endif

        return MesonDef;
}


G4ParticleDefinition * G4HadronBuilder::Barion(G4ParticleDefinition * black, 
                                              G4ParticleDefinition * white,Spin theSpin)
{

#ifdef G4VERBOSE
//  Verify Input Charge
   G4double charge =  black->GetPDGCharge() 
                    + white->GetPDGCharge();     
   if (std::abs(charge) > 2 || std::abs(3.*charge - 3*G4int(charge*1.001)) > perCent )
        {
            G4cerr << " G4HadronBuilder::Build()" << G4endl;
            G4cerr << "    Invalid total charge found for on input: " 
                        << charge<< G4endl;
            G4cerr << "    PGDcode input quark1/quark2 : " <<
                        black->GetPDGEncoding() << " / "<< 
                        white->GetPDGEncoding() << G4endl;
            G4cerr << G4endl;
        } 
#endif  
        G4int id1= black->GetPDGEncoding();
        G4int id2= white->GetPDGEncoding();
        if ( std::abs(id1) < std::abs(id2) )
           {
           G4int xchg = id1; 
           id1 = id2;  
           id2 = xchg;
           }

        if (std::abs(id1) < 1000 || std::abs(id2) > 3 ) 
           throw G4HadronicException(__FILE__, __LINE__, "G4HadronBuilder::Barion: Illegal quark content as input");   

        G4int ifl1= std::abs(id1)/1000;
        G4int ifl2 = (std::abs(id1) - ifl1 * 1000)/100;
        G4int diquarkSpin = std::abs(id1)%10; 
        G4int ifl3 = id2;
        if (id1 < 0)
           {
           ifl1 = - ifl1;
           ifl2 = - ifl2;
           }
        //... Construct barion, distinguish Lambda and Sigma barions.
        G4int kfla = std::abs(ifl1);
        G4int kflb = std::abs(ifl2);
        G4int kflc = std::abs(ifl3);

        G4int kfld = std::max(kfla,kflb);
              kfld = std::max(kfld,kflc);
        G4int kflf = std::min(kfla,kflb);
              kflf = std::min(kflf,kflc);

        G4int kfle = kfla + kflb + kflc - kfld - kflf;

        //... barion with content uuu or ddd or sss has always spin = 3/2
        theSpin = (kfla == kflb && kflb == kflc)? SpinThreeHalf : theSpin;   

        G4int kfll = 0;
        if(theSpin == SpinHalf && kfld > kfle && kfle > kflf) { 
// Spin J=1/2 and all three quarks different
// Two states exist: (uds -> lambda or sigma0)
//   -  lambda: s(ud)0 s : 3122; ie. reverse the two lighter quarks
//   -  sigma0: s(ud)1 s : 3212
           if(diquarkSpin == 1 ) {
              if ( kfla == kfld) {   // heaviest quark in diquark
                 kfll = 1;
              } else {
                 kfll = (G4int)(0.25 + G4UniformRand());
              }
           }   
           if(diquarkSpin == 3 && kfla != kfld)
               kfll = (G4int)(0.75 + G4UniformRand());
        }
        
        G4int PDGEncoding;
        if (kfll == 1)
           PDGEncoding = 1000 * kfld + 100 * kflf + 10 * kfle + theSpin;
        else    
           PDGEncoding = 1000 * kfld + 100 * kfle + 10 * kflf + theSpin;

        if (id1 < 0)
           PDGEncoding = -PDGEncoding;


        G4ParticleDefinition * BarionDef=
                G4ParticleTable::GetParticleTable()->FindParticle(PDGEncoding);
#ifdef G4VERBOSE
        if (BarionDef == 0 ) {
                G4cerr << " G4HadronBuilder - Warning: No particle for PDGcode= "
                       << PDGEncoding << G4endl;
        } else if  ( (  black->GetPDGCharge() + white->GetPDGCharge()
                        - BarionDef->GetPDGCharge() ) > perCent   ) {
                G4cerr << " G4HadronBuilder - Warning: Incorrect Charge : "
                        << " DiQuark/Quark = " 
                        << black->GetParticleName() << " / "
                        << white->GetParticleName() 
                        << " resulting Hadron " << BarionDef->GetParticleName() 
                        << G4endl;
        }
#endif

        return BarionDef;
}

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