Gabriele Cosmo
177 lines
5.7 KiB
C++
177 lines
5.7 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: G4NeutronBetaDecayChannel.cc,v 1.4 2002/04/03 09:05:33 kurasige Exp $
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// GEANT4 tag $Name: geant4-04-01 $
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//
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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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// History: first implementation, based on object model of
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// 18 Sep 2001 H.Kurashige
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//
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// ------------------------------------------------------------
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#include "G4ParticleDefinition.hh"
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#include "G4DecayProducts.hh"
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#include "G4VDecayChannel.hh"
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#include "G4NeutronBetaDecayChannel.hh"
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#include "Randomize.hh"
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#include "G4RotationMatrix.hh"
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#include "G4LorentzVector.hh"
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#include "G4LorentzRotation.hh"
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G4NeutronBetaDecayChannel::G4NeutronBetaDecayChannel(
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const G4String& theParentName,
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G4double theBR)
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:G4VDecayChannel("Neutron Decay"),
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aENuCorr(-0.102)
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{
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// set names for daughter particles
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if (theParentName == "neutron") {
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SetBR(theBR);
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SetParent("neutron");
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SetNumberOfDaughters(3);
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SetDaughter(0, "e-");
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SetDaughter(1, "anti_nu_e");
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SetDaughter(2, "proton");
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} else {
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#ifdef G4VERBOSE
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if (GetVerboseLevel()>0) {
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G4cout << "G4NeutronBetaDecayChannel:: constructor :";
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G4cout << " parent particle is not muon but ";
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G4cout << theParentName << G4endl;
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}
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#endif
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}
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}
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G4NeutronBetaDecayChannel::~G4NeutronBetaDecayChannel()
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{
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}
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G4DecayProducts *G4NeutronBetaDecayChannel::DecayIt(G4double)
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{
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// This class describes free neutron beta decay kinemtics.
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// This version neglects neutron/electron polarization
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// without Coulomb effect
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#ifdef G4VERBOSE
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if (GetVerboseLevel()>1) G4cout << "G4NeutronBetaDecayChannel::DecayIt ";
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#endif
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if (parent == 0) FillParent();
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if (daughters == 0) FillDaughters();
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// parent mass
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G4double parentmass = parent->GetPDGMass();
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//daughters'mass
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G4double daughtermass[3];
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G4double sumofdaughtermass = 0.0;
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for (G4int index=0; index<3; index++){
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daughtermass[index] = daughters[index]->GetPDGMass();
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sumofdaughtermass += daughtermass[index];
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}
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G4double xmax = parentmass-sumofdaughtermass;
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//create parent G4DynamicParticle at rest
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G4ThreeVector dummy;
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G4DynamicParticle * parentparticle = new G4DynamicParticle( parent, dummy, 0.0);
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//create G4Decayproducts
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G4DecayProducts *products = new G4DecayProducts(*parentparticle);
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delete parentparticle;
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// calculate daughter momentum
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G4double daughtermomentum[3];
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// calcurate electron energy
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G4double x; // Ee
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G4double p; // Pe
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G4double m = daughtermass[0]; //Me
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G4double w; // cosine of e-nu angle
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G4double r;
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G4double r0;
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do {
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x = xmax*G4UniformRand();
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p = sqrt(x*(x+2.0*m));
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w = 1.0-2.0*G4UniformRand();
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r = p*(x+m)*(xmax-x)*(xmax-x)*(1.0+aENuCorr*p/(x+m)*w);
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r0 = G4UniformRand()*(xmax+m)*(xmax+m)*xmax*xmax*(1.0+aENuCorr);
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} while (r < r0);
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//create daughter G4DynamicParticle
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// rotation materix to lab frame
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G4double costheta = 2.*G4UniformRand()-1.0;
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G4double theta = acos(costheta)*rad;
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G4double phi = 2.0*M_PI*G4UniformRand()*rad;
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G4RotationMatrix rm;
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rm.rotateY(theta);
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rm.rotateZ(phi);
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// daughter 0 (electron) in Z direction
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daughtermomentum[0] = p;
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G4ThreeVector direction0(0.0, 0.0, 1.0);
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direction0 = rm * direction0;
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G4DynamicParticle * daughterparticle0
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= new G4DynamicParticle( daughters[0], direction0*daughtermomentum[0]);
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products->PushProducts(daughterparticle0);
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// daughter 1 (nutrino) in XZ plane
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G4double eNu = xmax-x;
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G4double cosn = w;
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G4double sinn = sqrt((1.0-cosn)*(1.0+cosn));
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G4ThreeVector direction1(sinn, 0.0, cosn);
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direction1 = rm * direction1;
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G4DynamicParticle * daughterparticle1
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= new G4DynamicParticle( daughters[1], direction1*eNu);
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products->PushProducts(daughterparticle1);
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// daughter 2 (proton) at REST
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G4ThreeVector direction2(0.0, 0.0, 0.0);
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G4DynamicParticle * daughterparticle2
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= new G4DynamicParticle( daughters[2], direction2);
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products->PushProducts(daughterparticle2);
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// output message
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#ifdef G4VERBOSE
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if (GetVerboseLevel()>1) {
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G4cout << "G4NeutronBetaDecayChannel::DecayIt ";
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G4cout << " create decay products in rest frame " <<G4endl;
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products->DumpInfo();
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}
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#endif
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return products;
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}
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