Gabriele Cosmo
336 lines
12 KiB
C++
336 lines
12 KiB
C++
// This code implementation is the intellectual property of
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// the RD44 GEANT4 collaboration.
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//
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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 statement,
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// and all its terms.
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//
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// $Id: G4LEPionPlusInelastic.cc,v 2.4 1998/12/14 15:33:15 hpw Exp $
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// GEANT4 tag $Name: geant4-00 $
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//
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// Hadronic Process: PionPlus Inelastic Process
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// J.L. Chuma, TRIUMF, 19-Nov-1996
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// Last modified: 27-Mar-1997
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// Modified by J.L.Chuma 30-Apr-97: added originalTarget for CalculateMomenta
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#include "G4LEPionPlusInelastic.hh"
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#include "Randomize.hh"
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G4VParticleChange *
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G4LEPionPlusInelastic::ApplyYourself( const G4Track &aTrack,
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G4Nucleus &targetNucleus )
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{
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theParticleChange.Initialize( aTrack );
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const G4DynamicParticle *originalIncident = aTrack.GetDynamicParticle();
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if (originalIncident->GetKineticEnergy()<= 0.1*MeV) return &theParticleChange;
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// create the target particle
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G4DynamicParticle *originalTarget = targetNucleus.ReturnTargetParticle();
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G4double targetMass = originalTarget->GetDefinition()->GetPDGMass();
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G4ReactionProduct targetParticle( originalTarget->GetDefinition() );
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if( verboseLevel > 1 )
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{
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G4Material *targetMaterial = aTrack.GetMaterial();
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G4cout << "G4LEPionPlusInelastic::ApplyYourself called" << endl;
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G4cout << "kinetic energy = " << originalIncident->GetKineticEnergy() << "MeV, ";
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G4cout << "target material = " << targetMaterial->GetName() << ", ";
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G4cout << "target particle = " << originalTarget->GetDefinition()->GetParticleName()
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<< endl;
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}
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G4ReactionProduct currentParticle( originalIncident->GetDefinition() );
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currentParticle.SetMomentum( originalIncident->GetMomentum() );
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currentParticle.SetKineticEnergy( originalIncident->GetKineticEnergy() );
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// Fermi motion and evaporation
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// As of Geant3, the Fermi energy calculation had not been Done
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G4double ek = originalIncident->GetKineticEnergy();
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G4double amas = originalIncident->GetDefinition()->GetPDGMass();
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G4double tkin = targetNucleus.Cinema( ek );
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ek += tkin;
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currentParticle.SetKineticEnergy( ek );
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G4double et = ek + amas;
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G4double p = sqrt( abs((et-amas)*(et+amas)) );
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G4double pp = currentParticle.GetMomentum().mag();
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if( pp > 0.0 )
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{
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G4ThreeVector momentum = currentParticle.GetMomentum();
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currentParticle.SetMomentum( momentum * (p/pp) );
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}
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// calculate black track energies
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tkin = targetNucleus.EvaporationEffects( ek );
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ek -= tkin;
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currentParticle.SetKineticEnergy( ek );
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et = ek + amas;
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p = sqrt( abs((et-amas)*(et+amas)) );
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pp = currentParticle.GetMomentum().mag();
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if( pp > 0.0 )
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{
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G4ThreeVector momentum = currentParticle.GetMomentum();
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currentParticle.SetMomentum( momentum * (p/pp) );
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}
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G4ReactionProduct modifiedOriginal = currentParticle;
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currentParticle.SetSide( 1 ); // incident always goes in forward hemisphere
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targetParticle.SetSide( -1 ); // target always goes in backward hemisphere
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G4bool incidentHasChanged = false;
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G4bool targetHasChanged = false;
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G4bool quasiElastic = false;
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G4FastVector<G4ReactionProduct,128> vec; // vec will contain the secondary particles
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G4int vecLen = 0;
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vec.Initialize( 0 );
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const G4double cutOff = 0.1*MeV;
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if( currentParticle.GetKineticEnergy() > cutOff )
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Cascade( vec, vecLen,
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originalIncident, currentParticle, targetParticle,
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incidentHasChanged, targetHasChanged, quasiElastic );
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CalculateMomenta( vec, vecLen,
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originalIncident, originalTarget, modifiedOriginal,
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targetNucleus, currentParticle, targetParticle,
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incidentHasChanged, targetHasChanged, quasiElastic );
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SetUpChange( vec, vecLen,
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currentParticle, targetParticle,
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incidentHasChanged );
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delete originalTarget;
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return &theParticleChange;
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}
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void
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G4LEPionPlusInelastic::Cascade(
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G4FastVector<G4ReactionProduct,128> &vec,
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G4int& vecLen,
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const G4DynamicParticle *originalIncident,
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G4ReactionProduct ¤tParticle,
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G4ReactionProduct &targetParticle,
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G4bool &incidentHasChanged,
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G4bool &targetHasChanged,
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G4bool &quasiElastic )
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{
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// derived from original FORTRAN code CASPIP by H. Fesefeldt (18-Sep-1987)
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//
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// pi+ undergoes interaction with nucleon within nucleus.
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// Check if energetically possible to produce pions/kaons.
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// If not assume nuclear excitation occurs and input particle
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// is degraded in energy. No other particles produced.
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// If reaction is possible find correct number of pions/protons/neutrons
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// produced using an interpolation to multiplicity data.
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// Replace some pions or protons/neutrons by kaons or strange baryons
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// according to average multiplicity per inelastic reactions.
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//
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const G4double mOriginal = originalIncident->GetDefinition()->GetPDGMass();
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const G4double etOriginal = originalIncident->GetTotalEnergy();
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const G4double targetMass = targetParticle.GetMass();
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G4double centerofmassEnergy = sqrt( mOriginal*mOriginal +
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targetMass*targetMass +
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2.0*targetMass*etOriginal );
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G4double availableEnergy = centerofmassEnergy-(targetMass+mOriginal);
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if( availableEnergy <= G4PionPlus::PionPlus()->GetPDGMass() )
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{
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quasiElastic = true;
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return;
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}
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static G4bool first = true;
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const G4int numMul = 1200;
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const G4int numSec = 60;
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static G4double protmul[numMul], protnorm[numSec]; // proton constants
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static G4double neutmul[numMul], neutnorm[numSec]; // neutron constants
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// np = number of pi+, nm = number of pi-, nz = number of pi0
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G4int counter, nt=0, np=0, nm=0, nz=0;
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const G4double c = 1.25;
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const G4double b[] = { 0.70, 0.70 };
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if( first ) { // compute normalization constants, this will only be Done once
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first = false;
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G4int i;
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for( i=0; i<numMul; ++i )protmul[i] = 0.0;
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for( i=0; i<numSec; ++i )protnorm[i] = 0.0;
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counter = -1;
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for( np=0; np<(numSec/3); ++np ) {
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for( nm=max(0,np-2); nm<=np; ++nm ) {
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for( nz=0; nz<numSec/3; ++nz ) {
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if( ++counter < numMul ) {
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nt = np+nm+nz;
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if( nt > 0 ) {
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protmul[counter] = Pmltpc(np,nm,nz,nt,b[0],c);
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protnorm[nt-1] += protmul[counter];
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}
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}
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}
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}
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}
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for( i=0; i<numMul; ++i )neutmul[i] = 0.0;
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for( i=0; i<numSec; ++i )neutnorm[i] = 0.0;
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counter = -1;
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for( np=0; np<numSec/3; ++np ) {
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for( nm=max(0,np-1); nm<=(np+1); ++nm ) {
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for( nz=0; nz<numSec/3; ++nz ) {
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if( ++counter < numMul ) {
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nt = np+nm+nz;
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if( (nt>0) && (nt<=numSec) ) {
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neutmul[counter] = Pmltpc(np,nm,nz,nt,b[1],c);
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neutnorm[nt-1] += neutmul[counter];
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}
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}
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}
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}
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}
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for( i=0; i<numSec; ++i ) {
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if( protnorm[i] > 0.0 )protnorm[i] = 1.0/protnorm[i];
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if( neutnorm[i] > 0.0 )neutnorm[i] = 1.0/neutnorm[i];
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}
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} // end of initialization
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const G4double expxu = 82.; // upper bound for arg. of exp
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const G4double expxl = -expxu; // lower bound for arg. of exp
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G4ParticleDefinition *aNeutron = G4Neutron::Neutron();
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G4ParticleDefinition *aProton = G4Proton::Proton();
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G4ParticleDefinition *aPiZero = G4PionZero::PionZero();
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G4int ieab = availableEnergy*5.0/GeV;
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const G4double supp[] = {0.,0.2,0.45,0.55,0.65,0.75,0.85,0.90,0.94,0.98};
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G4double test, w0, wp, wt, wm;
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if( (availableEnergy < 2.0*GeV) && (G4UniformRand() >= supp[ieab]) )
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{
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// suppress high multiplicity events at low momentum
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// only one pion will be produced
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nm = np = nz = 0;
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if( targetParticle.GetDefinition() == aProton ) {
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test = exp( min( expxu, max( expxl, -sqr(1.0+b[0])/(2.0*c*c) ) ) );
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w0 = test;
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wp = test;
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if( G4UniformRand() < w0/(w0+wp) )
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nz =1;
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else
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np = 1;
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} else { // target is a neutron
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test = exp( min( expxu, max( expxl, -sqr(1.0+b[1])/(2.0*c*c) ) ) );
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w0 = test;
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wp = test;
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test = exp( min( expxu, max( expxl, -sqr(-1.0+b[1])/(2.0*c*c) ) ) );
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wm = test;
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wt = w0+wp+wm;
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wp = w0+wp;
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G4double ran = G4UniformRand();
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if( ran < w0/wt )
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nz = 1;
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else if( ran < wp/wt )
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np = 1;
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else
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nm = 1;
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}
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} else {
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G4double n, anpn;
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GetNormalizationConstant( availableEnergy, n, anpn );
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G4double ran = G4UniformRand();
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G4double dum, excs = 0.0;
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if( targetParticle.GetDefinition() == aProton ) {
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counter = -1;
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for( np=0; (np<numSec/3) && (ran>=excs); ++np ) {
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for( nm=max(0,np-2); (nm<=np) && (ran>=excs); ++nm ) {
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for( nz=0; (nz<numSec/3) && (ran>=excs); ++nz ) {
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if( ++counter < numMul ) {
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nt = np+nm+nz;
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if( nt > 0 ) {
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test = exp( min( expxu, max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
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dum = (pi/anpn)*nt*protmul[counter]*protnorm[nt-1]/(2.0*n*n);
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if( fabs(dum) < 1.0 ) {
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if( test >= 1.0e-10 )excs += dum*test;
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} else {
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excs += dum*test;
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}
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}
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}
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}
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}
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}
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if( ran >= excs )
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{
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quasiElastic = true;
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return; // 3 previous loops continued to the end
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}
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np--; nm--; nz--;
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} else { // target must be a neutron
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counter = -1;
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for( np=0; (np<numSec/3) && (ran>=excs); ++np ) {
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for( nm=max(0,np-1); (nm<=(np+1)) && (ran>=excs); ++nm ) {
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for( nz=0; (nz<numSec/3) && (ran>=excs); ++nz ) {
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if( ++counter < numMul ) {
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nt = np+nm+nz;
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if( (nt>=1) && (nt<=numSec) ) {
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test = exp( min( expxu, max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
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dum = (pi/anpn)*nt*neutmul[counter]*neutnorm[nt-1]/(2.0*n*n);
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if( fabs(dum) < 1.0 ) {
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if( test >= 1.0e-10 )excs += dum*test;
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} else {
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excs += dum*test;
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}
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}
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}
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}
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}
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}
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if( ran >= excs ) // 3 previous loops continued to the end
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{
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quasiElastic = true;
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return; // 3 previous loops continued to the end
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}
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np--; nm--; nz--;
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}
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}
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if( targetParticle.GetDefinition() == aProton ) {
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switch( np-nm ) {
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case 1:
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if( G4UniformRand() < 0.5 ) {
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currentParticle.SetDefinitionAndUpdateE( aPiZero );
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incidentHasChanged = true;
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} else {
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targetParticle.SetDefinitionAndUpdateE( aNeutron );
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targetHasChanged = true;
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}
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break;
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case 2:
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currentParticle.SetDefinitionAndUpdateE( aPiZero );
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targetParticle.SetDefinitionAndUpdateE( aNeutron );
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incidentHasChanged = true;
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targetHasChanged = true;
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break;
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default:
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break;
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}
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} else {
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switch( np-nm ) {
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case 0:
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if( G4UniformRand() < 0.25 ) {
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currentParticle.SetDefinitionAndUpdateE( aPiZero );
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targetParticle.SetDefinitionAndUpdateE( aProton );
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incidentHasChanged = true;
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targetHasChanged = true;
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}
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break;
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case 1:
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currentParticle.SetDefinitionAndUpdateE( aPiZero );
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incidentHasChanged = true;
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break;
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default:
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targetParticle.SetDefinitionAndUpdateE( aProton );
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targetHasChanged = true;
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break;
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}
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}
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SetUpPions( np, nm, nz, vec, vecLen );
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return;
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}
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/* end of file */
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