source: trunk/source/processes/hadronic/models/util/src/G4SampleResonance.cc@ 1347

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// ------------------------------------------------------------
//      GEANT 4 class header file
//
//      ---------------- G4SampleResonance ----------------
//             by Henning Weber, March 2001.
//      helper class for sampling resonance masses
// ------------------------------------------------------------


#include "globals.hh"
#include <iostream>
#include "G4SampleResonance.hh"
#include "G4DecayTable.hh"
#include "Randomize.hh"
#include "G4HadronicException.hh"

G4SampleResonance::minMassMapType G4SampleResonance::minMassCache;

G4double G4SampleResonance::GetMinimumMass(const G4ParticleDefinition* p) const
{
  
  G4double minResonanceMass = DBL_MAX;

  if ( p->IsShortLived() ) 
    {
      minMassMapIterator i = minMassCache.find(p);
      if ( i!=minMassCache.end() ) 
        {
          minResonanceMass = (*i).second; 
        } 
      else 
        {
          // G4cout << "--> request for " << p->GetParticleName() << G4endl;

          const G4DecayTable* theDecays = const_cast<G4ParticleDefinition*>(p)->GetDecayTable();
          const G4int nDecays = theDecays->entries();
      
          for (G4int i=0; i<nDecays; i++) 
            {
              const G4VDecayChannel* aDecay = theDecays->GetDecayChannel(i);
              const G4int nDaughters = aDecay->GetNumberOfDaughters();
              
              G4double minChannelMass = 0;
              
              for (G4int j=0; j<nDaughters; j++) 
                {
                  const G4ParticleDefinition* aDaughter = const_cast<G4VDecayChannel*>(aDecay)->GetDaughter(j);
                  G4double minMass = GetMinimumMass(aDaughter);
                  if (!minMass) minMass = DBL_MAX; // exclude gamma channel;
                  minChannelMass+=minMass;
                }
              // G4cout << "channel mass for the above is " << minChannelMass/MeV << G4endl;
              if (minChannelMass < minResonanceMass) minResonanceMass = minChannelMass;
              
            }
          // replace this as soon as the compiler supports mutable!!
          G4SampleResonance* self = const_cast<G4SampleResonance*>(this);
          (self->minMassCache)[p] = minResonanceMass;
          
        }
    } 
  else 
    {
    
      minResonanceMass = p->GetPDGMass();
      
    }
  // G4cout << "minimal mass for " << p->GetParticleName() << " is " << minResonanceMass/MeV << G4endl;
  
  return minResonanceMass;
} 
      


G4double G4SampleResonance::SampleMass(const G4ParticleDefinition* p, const G4double maxMass) const
{
  return SampleMass(p->GetPDGMass(), p->GetPDGWidth(), GetMinimumMass(p), maxMass);
}


G4double G4SampleResonance::SampleMass(const G4double poleMass, 
                                       const G4double gamma,
                                       const G4double minMass,
                                       const G4double maxMass) const
{
  // Chooses a mass randomly between minMass and maxMass 
  //     according to a Breit-Wigner function with constant 
  //     width gamma and pole poleMass

  if ( minMass > maxMass ) 
    {
      throw G4HadronicException(__FILE__, __LINE__,
           "SampleResonanceMass: mass range negative (minMass>maxMass)");
    }

  G4double returnMass;

  if ( gamma < DBL_EPSILON ) 
    {
      returnMass = std::max(minMass, std::min(maxMass, poleMass));
    } 
  else 
    {
      double fmin = BrWigInt0(minMass, gamma, poleMass);
      double fmax = BrWigInt0(maxMass, gamma, poleMass);
      double f = fmin + (fmax-fmin)*G4UniformRand();
      returnMass = BrWigInv(f, gamma, poleMass);      
    }

  return returnMass;
}