Gabriele Cosmo
141 lines
4.7 KiB
C++
141 lines
4.7 KiB
C++
//
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// ********************************************************************
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// * DISCLAIMER *
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// * *
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// * The following disclaimer summarizes all the specific disclaimers *
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// * of contributors to this software. The specific disclaimers,which *
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// * govern, are listed with their locations in: *
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// * http://cern.ch/geant4/license *
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// * *
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// * Neither the authors of this software system, nor their employing *
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// * institutes,nor the agencies providing financial support for this *
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// * work make any representation or warranty, express or implied, *
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// * regarding this software system or assume any liability for its *
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// * use. *
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// * *
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// * This code implementation is the intellectual property of the *
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// * GEANT4 collaboration. *
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// * By copying, distributing or modifying the Program (or any work *
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// * based on the Program) you indicate your acceptance of this *
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// * statement, and all its terms. *
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// ********************************************************************
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//
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//
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// $Id: G4SampleResonance.cc,v 1.5 2002/12/12 19:17:58 gunter Exp $
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// GEANT4 tag $Name: geant4-05-01 $
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//
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// ------------------------------------------------------------
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// GEANT 4 class header file
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//
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// ---------------- G4SampleResonance ----------------
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// by Henning Weber, March 2001.
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// helper class for sampling resonance masses
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// ------------------------------------------------------------
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#include "globals.hh"
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#include "g4std/iostream"
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#include "G4SampleResonance.hh"
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#include "G4DecayTable.hh"
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#include "Randomize.hh"
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G4SampleResonance::minMassMapType G4SampleResonance::minMassCache;
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G4double G4SampleResonance::GetMinimumMass(const G4ParticleDefinition* p) const
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{
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G4double minResonanceMass = DBL_MAX;
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if ( p->IsShortLived() )
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{
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minMassMapIterator i = minMassCache.find(p);
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if ( i!=minMassCache.end() )
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{
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minResonanceMass = (*i).second;
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}
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else
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{
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// G4cout << "--> request for " << p->GetParticleName() << G4endl;
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const G4DecayTable* theDecays = const_cast<G4ParticleDefinition*>(p)->GetDecayTable();
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const G4int nDecays = theDecays->entries();
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for (G4int i=0; i<nDecays; i++)
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{
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const G4VDecayChannel* aDecay = theDecays->GetDecayChannel(i);
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const G4int nDaughters = aDecay->GetNumberOfDaughters();
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G4double minChannelMass = 0;
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for (G4int j=0; j<nDaughters; j++)
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{
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const G4ParticleDefinition* aDaughter = const_cast<G4VDecayChannel*>(aDecay)->GetDaughter(j);
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G4double minMass = GetMinimumMass(aDaughter);
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if (!minMass) minMass = DBL_MAX; // exclude gamma channel;
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minChannelMass+=minMass;
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}
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// G4cout << "channel mass for the above is " << minChannelMass/MeV << G4endl;
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if (minChannelMass < minResonanceMass) minResonanceMass = minChannelMass;
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}
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// replace this as soon as the compiler supports mutable!!
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G4SampleResonance* self = const_cast<G4SampleResonance*>(this);
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(self->minMassCache)[p] = minResonanceMass;
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}
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}
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else
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{
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minResonanceMass = p->GetPDGMass();
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}
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// G4cout << "minimal mass for " << p->GetParticleName() << " is " << minResonanceMass/MeV << G4endl;
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return minResonanceMass;
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}
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G4double G4SampleResonance::SampleMass(const G4ParticleDefinition* p, const G4double maxMass) const
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{
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return SampleMass(p->GetPDGMass(), p->GetPDGWidth(), GetMinimumMass(p), maxMass);
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}
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G4double G4SampleResonance::SampleMass(const G4double poleMass,
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const G4double gamma,
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const G4double minMass,
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const G4double maxMass) const
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{
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// Chooses a mass randomly between minMass and maxMass
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// according to a Breit-Wigner function with constant
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// width gamma and pole poleMass
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if ( minMass > maxMass )
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{
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G4Exception("SampleResonanceMass: mass range negative (minMass>maxMass)");
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}
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G4double returnMass;
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if ( gamma < DBL_EPSILON )
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{
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returnMass = G4std::max(minMass, G4std::min(maxMass, poleMass));
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}
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else
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{
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double fmin = BrWigInt0(minMass, gamma, poleMass);
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double fmax = BrWigInt0(maxMass, gamma, poleMass);
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double f = fmin + (fmax-fmin)*G4UniformRand();
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returnMass = BrWigInv(f, gamma, poleMass);
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}
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return returnMass;
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}
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