203 lines
6.2 KiB
C++
203 lines
6.2 KiB
C++
// Geant4 simulation for MuSR
|
|
// AUTHOR: Toni SHIROKA, Paul Scherrer Institut, PSI
|
|
// DATE : 2008-05
|
|
//
|
|
|
|
//
|
|
// ********************************************************************
|
|
// * 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: MuDecayChannel.cc,v 1.17 2006/06/29 19:25:34 gunter Exp $
|
|
// GEANT4 tag $Name: geant4-09-00 $
|
|
//
|
|
//
|
|
// ------------------------------------------------------------
|
|
// 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
|
|
//2005
|
|
// M. Melissas ( melissas AT cppm.in2p3.fr)
|
|
// J. Brunner ( brunner AT cppm.in2p3.fr)
|
|
// Adding V-A fluxes for neutrinos using a new algortithm :
|
|
// ------------------------------------------------------------
|
|
|
|
#include "G4ParticleDefinition.hh"
|
|
#include "G4DecayProducts.hh"
|
|
#include "G4VDecayChannel.hh"
|
|
#include "MuDecayChannel.hh"
|
|
#include "Randomize.hh"
|
|
#include "G4LorentzVector.hh"
|
|
#include "G4LorentzRotation.hh"
|
|
#include "G4RotationMatrix.hh"
|
|
|
|
MuDecayChannel::MuDecayChannel(const G4String& theParentName,
|
|
G4double theBR)
|
|
:G4VDecayChannel("Muonium Decay",1)
|
|
{
|
|
// set names for daughter particles
|
|
if (theParentName == "Mu") {
|
|
SetBR(theBR);
|
|
SetParent("Mu");
|
|
SetNumberOfDaughters(3);
|
|
SetDaughter(0, "e+");
|
|
SetDaughter(1, "nu_e");
|
|
SetDaughter(2, "anti_nu_mu");
|
|
} else {
|
|
#ifdef G4VERBOSE
|
|
if (GetVerboseLevel()>0) {
|
|
G4cout << "MuDecayChannel:: constructor :";
|
|
G4cout << " parent particle is not muon but ";
|
|
G4cout << theParentName << G4endl;
|
|
}
|
|
#endif
|
|
}
|
|
}
|
|
|
|
MuDecayChannel::~MuDecayChannel()
|
|
{
|
|
}
|
|
|
|
G4DecayProducts *MuDecayChannel::DecayIt(G4double)
|
|
{
|
|
// this version neglects muon polarization,and electron mass
|
|
// assumes the pure V-A coupling
|
|
// the Neutrinos are correctly V-A.
|
|
#ifdef G4VERBOSE
|
|
if (GetVerboseLevel()>1) G4cout << "MuDecayChannel::DecayIt ";
|
|
#endif
|
|
|
|
if (parent == 0) FillParent();
|
|
if (daughters == 0) FillDaughters();
|
|
|
|
// parent mass
|
|
G4double parentmass = parent->GetPDGMass();
|
|
|
|
//daughters'mass
|
|
G4double daughtermass[3];
|
|
G4double sumofdaughtermass = 0.0;
|
|
for (G4int index=0; index<3; index++){
|
|
daughtermass[index] = daughters[index]->GetPDGMass();
|
|
sumofdaughtermass += daughtermass[index];
|
|
}
|
|
|
|
//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 electron energy
|
|
G4double xmax = (1.0+daughtermass[0]*daughtermass[0]/parentmass/parentmass);
|
|
G4double x;
|
|
|
|
G4double Ee,Ene;
|
|
|
|
G4double gam;
|
|
G4double EMax=parentmass/2-daughtermass[0];
|
|
|
|
|
|
//Generating Random Energy
|
|
do {
|
|
Ee=G4UniformRand();
|
|
do{
|
|
x=xmax*G4UniformRand();
|
|
gam=G4UniformRand();
|
|
}while (gam >x*(1.-x));
|
|
Ene=x;
|
|
} while ( Ene < (1.-Ee));
|
|
G4double Enm=(2.-Ee-Ene);
|
|
|
|
|
|
//initialisation of rotation parameters
|
|
|
|
G4double costheta,sintheta,rphi,rtheta,rpsi;
|
|
costheta= 1.-2./Ee-2./Ene+2./Ene/Ee;
|
|
sintheta=std::sqrt(1.-costheta*costheta);
|
|
|
|
|
|
rphi=twopi*G4UniformRand()*rad;
|
|
rtheta=(std::acos(2.*G4UniformRand()-1.));
|
|
rpsi=twopi*G4UniformRand()*rad;
|
|
|
|
G4RotationMatrix rot;
|
|
rot.set(rphi,rtheta,rpsi);
|
|
|
|
//electron 0
|
|
daughtermomentum[0]=std::sqrt(Ee*Ee*EMax*EMax+2.0*Ee*EMax * daughtermass[0]);
|
|
G4ThreeVector direction0(0.0,0.0,1.0);
|
|
|
|
direction0 *= rot;
|
|
|
|
G4DynamicParticle * daughterparticle = new G4DynamicParticle ( daughters[0], direction0 * daughtermomentum[0]);
|
|
|
|
products->PushProducts(daughterparticle);
|
|
|
|
//electronic neutrino 1
|
|
|
|
daughtermomentum[1]=std::sqrt(Ene*Ene*EMax*EMax+2.0*Ene*EMax * daughtermass[1]);
|
|
G4ThreeVector direction1(sintheta,0.0,costheta);
|
|
|
|
direction1 *= rot;
|
|
|
|
G4DynamicParticle * daughterparticle1 = new G4DynamicParticle ( daughters[1], direction1 * daughtermomentum[1]);
|
|
products->PushProducts(daughterparticle1);
|
|
|
|
//muonic neutrino 2
|
|
|
|
daughtermomentum[2]=std::sqrt(Enm*Enm*EMax*EMax +2.0*Enm*EMax*daughtermass[2]);
|
|
G4ThreeVector direction2(-Ene/Enm*sintheta,0,-Ee/Enm-Ene/Enm*costheta);
|
|
|
|
direction2 *= rot;
|
|
|
|
G4DynamicParticle * daughterparticle2 = new G4DynamicParticle ( daughters[2],
|
|
direction2 * daughtermomentum[2]);
|
|
products->PushProducts(daughterparticle2);
|
|
|
|
|
|
|
|
|
|
// output message
|
|
#ifdef G4VERBOSE
|
|
if (GetVerboseLevel()>1) {
|
|
G4cout << "MuDecayChannel::DecayIt ";
|
|
G4cout << " create decay products in rest frame " <<G4endl;
|
|
products->DumpInfo();
|
|
}
|
|
#endif
|
|
return products;
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|