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geant4/source/particles/management/src/G4TauLeptonicDecayChannel.cc
T
Gabriele Cosmo b1eb5424d2 Import Geant4 9.5.0 source tree
2016-06-09 16:46:55 +02:00

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//
// ********************************************************************
// * License and Disclaimer *
// * *
// * The Geant4 software is copyright of the Copyright Holders of *
// * the Geant4 Collaboration. It is provided under the terms and *
// * conditions of the Geant4 Software License, included in the file *
// * LICENSE and available at http://cern.ch/geant4/license . These *
// * include a list of copyright holders. *
// * *
// * Neither the authors of this software system, nor their employing *
// * institutes,nor the agencies providing financial support for this *
// * work make any representation or warranty, express or implied, *
// * regarding this software system or assume any liability for its *
// * use. Please see the license in the file LICENSE and URL above *
// * for the full disclaimer and the limitation of liability. *
// * *
// * This code implementation is the result of the scientific and *
// * technical work of the GEANT4 collaboration. *
// * By using, copying, modifying or distributing the software (or *
// * any work based on the software) you agree to acknowledge its *
// * use in resulting scientific publications, and indicate your *
// * acceptance of all terms of the Geant4 Software license. *
// ********************************************************************
//
//
// $Id: G4TauLeptonicDecayChannel.cc,v 1.5 2006-06-29 19:26:18 gunter Exp $
// GEANT4 tag $Name: not supported by cvs2svn $
//
//
// ------------------------------------------------------------
// GEANT 4 class header file
//
// History: first implementation, based on object model of
// 30 May 1997 H.Kurashige
//
// Fix bug in calcuration of electron energy in DecayIt 28 Feb. 01 H.Kurashige
// ------------------------------------------------------------
#include "G4ParticleDefinition.hh"
#include "G4DecayProducts.hh"
#include "G4VDecayChannel.hh"
#include "G4TauLeptonicDecayChannel.hh"
#include "Randomize.hh"
#include "G4LorentzVector.hh"
#include "G4LorentzRotation.hh"
G4TauLeptonicDecayChannel::G4TauLeptonicDecayChannel()
:G4VDecayChannel()
{
}
G4TauLeptonicDecayChannel::G4TauLeptonicDecayChannel(
const G4String& theParentName,
G4double theBR,
const G4String& theLeptonName)
:G4VDecayChannel("Tau Leptonic Decay",1)
{
// set names for daughter particles
if (theParentName == "tau+") {
SetBR(theBR);
SetParent("tau+");
SetNumberOfDaughters(3);
if ((theLeptonName=="e-"||theLeptonName=="e+")){
SetDaughter(0, "e+");
SetDaughter(1, "nu_e");
SetDaughter(2, "anti_nu_tau");
} else {
SetDaughter(0, "mu+");
SetDaughter(1, "nu_mu");
SetDaughter(2, "anti_nu_tau");
}
} else if (theParentName == "tau-") {
SetBR(theBR);
SetParent("tau-");
SetNumberOfDaughters(3);
if ((theLeptonName=="e-"||theLeptonName=="e+")){
SetDaughter(0, "e-");
SetDaughter(1, "anti_nu_e");
SetDaughter(2, "nu_tau");
} else {
SetDaughter(0, "mu-");
SetDaughter(1, "anti_nu_mu");
SetDaughter(2, "nu_tau");
}
} else {
#ifdef G4VERBOSE
if (GetVerboseLevel()>0) {
G4cout << "G4TauLeptonicDecayChannel:: constructor :";
G4cout << " parent particle is not tau but ";
G4cout << theParentName << G4endl;
}
#endif
}
}
G4TauLeptonicDecayChannel::~G4TauLeptonicDecayChannel()
{
}
G4TauLeptonicDecayChannel::G4TauLeptonicDecayChannel(const G4TauLeptonicDecayChannel &right):
G4VDecayChannel(right)
{
}
G4TauLeptonicDecayChannel & G4TauLeptonicDecayChannel::operator=(const G4TauLeptonicDecayChannel & right)
{
if (this != &right) {
kinematics_name = right.kinematics_name;
verboseLevel = right.verboseLevel;
rbranch = right.rbranch;
// copy parent name
parent_name = new G4String(*right.parent_name);
// clear daughters_name array
ClearDaughtersName();
// recreate array
numberOfDaughters = right.numberOfDaughters;
if ( numberOfDaughters >0 ) {
if (daughters_name !=0) ClearDaughtersName();
daughters_name = new G4String*[numberOfDaughters];
//copy daughters name
for (G4int index=0; index < numberOfDaughters; index++) {
daughters_name[index] = new G4String(*right.daughters_name[index]);
}
}
}
return *this;
}
G4DecayProducts *G4TauLeptonicDecayChannel::DecayIt(G4double)
{
// this version neglects muon polarization
// assumes the pure V-A coupling
// gives incorrect energy spectrum for neutrinos
#ifdef G4VERBOSE
if (GetVerboseLevel()>1) G4cout << "G4TauLeptonicDecayChannel::DecayIt ";
#endif
if (parent == 0) FillParent();
if (daughters == 0) FillDaughters();
// parent mass
G4double parentmass = parent->GetPDGMass();
//daughters'mass
G4double daughtermass[3];
for (G4int index=0; index<3; index++){
daughtermass[index] = daughters[index]->GetPDGMass();
}
//create parent G4DynamicParticle at rest
G4ThreeVector dummy;
G4DynamicParticle * parentparticle = new G4DynamicParticle( parent, dummy, 0.0);
//create G4Decayproducts
G4DecayProducts *products = new G4DecayProducts(*parentparticle);
delete parentparticle;
// calculate daughter momentum
G4double daughtermomentum[3];
// calcurate lepton momentum
G4double pmax = (parentmass*parentmass-daughtermass[0]*daughtermass[0])/2./parentmass;
G4double p, e;
G4double r;
do {
// determine momentum/energy
r = G4UniformRand();
p = pmax*G4UniformRand();
e = std::sqrt(p*p + daughtermass[0]*daughtermass[0]);
} while (r > spectrum(p,e,parentmass,daughtermass[0]) );
//create daughter G4DynamicParticle
// daughter 0 (lepton)
daughtermomentum[0] = p;
G4double costheta, sintheta, phi, sinphi, cosphi;
costheta = 2.*G4UniformRand()-1.0;
sintheta = std::sqrt((1.0-costheta)*(1.0+costheta));
phi = twopi*G4UniformRand()*rad;
sinphi = std::sin(phi);
cosphi = std::cos(phi);
G4ThreeVector direction0(sintheta*cosphi,sintheta*sinphi,costheta);
G4DynamicParticle * daughterparticle
= new G4DynamicParticle( daughters[0], direction0*daughtermomentum[0]);
products->PushProducts(daughterparticle);
// daughter 1 ,2 (nutrinos)
// create neutrinos in the C.M frame of two neutrinos
G4double energy2 = parentmass-e;
G4double vmass = std::sqrt((energy2-daughtermomentum[0])*(energy2+daughtermomentum[0]));
G4double beta = -1.0*daughtermomentum[0]/energy2;
G4double costhetan = 2.*G4UniformRand()-1.0;
G4double sinthetan = std::sqrt((1.0-costhetan)*(1.0+costhetan));
G4double phin = twopi*G4UniformRand()*rad;
G4double sinphin = std::sin(phin);
G4double cosphin = std::cos(phin);
G4ThreeVector direction1(sinthetan*cosphin,sinthetan*sinphin,costhetan);
G4DynamicParticle * daughterparticle1
= new G4DynamicParticle( daughters[1], direction1*(vmass/2.));
G4DynamicParticle * daughterparticle2
= new G4DynamicParticle( daughters[2], direction1*(-1.0*vmass/2.));
// boost to the muon rest frame
G4LorentzVector p4;
p4 = daughterparticle1->Get4Momentum();
p4.boost( direction0.x()*beta, direction0.y()*beta, direction0.z()*beta);
daughterparticle1->Set4Momentum(p4);
p4 = daughterparticle2->Get4Momentum();
p4.boost( direction0.x()*beta, direction0.y()*beta, direction0.z()*beta);
daughterparticle2->Set4Momentum(p4);
products->PushProducts(daughterparticle1);
products->PushProducts(daughterparticle2);
daughtermomentum[1] = daughterparticle1->GetTotalMomentum();
daughtermomentum[2] = daughterparticle2->GetTotalMomentum();
// output message
#ifdef G4VERBOSE
if (GetVerboseLevel()>1) {
G4cout << "G4TauLeptonicDecayChannel::DecayIt ";
G4cout << " create decay products in rest frame " <<G4endl;
products->DumpInfo();
}
#endif
return products;
}
G4double G4TauLeptonicDecayChannel::spectrum(G4double p,
G4double e,
G4double mtau,
G4double ml)
{
G4double f1;
f1 = 3.0*e*(mtau*mtau+ml*ml)-4.0*mtau*e*e-2.0*mtau*ml*ml;
return p*(f1)/(mtau*mtau*mtau*mtau)/(0.6);
}
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