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;
}