286 lines
8.1 KiB
C++
286 lines
8.1 KiB
C++
//$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$//*
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// LOW ENERGY MUON SPIN RELAXATION, ROTATION, RADIATION Geant4 SIMULATION
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// ID : LEMuSRMuonDecayChannel.cc , v 1.2
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// AUTHOR: Taofiq PARAISO based on G4MuonDecayChannel $Id$
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// DATE : 2004-07-13 11:15
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//
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// add muonium decay, PARAISO 07/04/2005
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//
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//$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$//
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//
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// & &&&&&&&&&& &&&&&&& &&&&&&&&
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// & & && && & &&
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// & & & & & & &&
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// & &&&&&&& & & &&&&&& &&&&&&&&
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// & & & && & & &&
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// & & && & & && && & &
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// &&&&&&&&&& &&&&&&&&&& & &&&&& && &&&&&&& & &&
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// &
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// &
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// &
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// &
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// MUON DECAY CHANNEL.CC
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//$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$//
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#include "Randomize.hh"
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#include "G4ios.hh"
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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 "LEMuSRMuonDecayChannel.hh"
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#include "Randomize.hh"
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#include "G4LorentzVector.hh"
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#include "G4LorentzRotation.hh"
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#include "G4Transform3D.hh"
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#include "G4UnitsTable.hh"
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#include "LEMuSRAtRestSpinRotation.hh"
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LEMuSRMuonDecayChannel::LEMuSRMuonDecayChannel(const G4String& theParentName,
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G4double theBR)
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:G4VDecayChannel("LEMuSR Muon Decay",1)
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{
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// set names for daughter particles
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if (theParentName == "mu+") {
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SetBR(theBR);
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SetParent("mu+");
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SetNumberOfDaughters(3);
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SetDaughter(0, "e+");
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SetDaughter(1, "nu_e");
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SetDaughter(2, "anti_nu_mu");
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} else if (theParentName == "mu-") {
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SetBR(theBR);
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SetParent("mu-");
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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, "nu_mu");
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}
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else if (theParentName == "Mu") {
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SetBR(theBR);
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SetParent("Mu");
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SetNumberOfDaughters(3);
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SetDaughter(0, "e+");
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SetDaughter(1, "nu_e");
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SetDaughter(2, "anti_nu_mu");
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}
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else {
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#ifdef G4VERBOSE
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if (GetVerboseLevel()>0) {
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G4cout << "LEMuSRMuonDecayChannel:: 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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// get the random number engine
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theEngine = HepRandom::getTheEngine();
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theParentPolarization=G4ThreeVector(0,0,0);
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pointer = this;
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}
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LEMuSRMuonDecayChannel* LEMuSRMuonDecayChannel::pointer=0;
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LEMuSRMuonDecayChannel* LEMuSRMuonDecayChannel::GetInstance()
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{
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return pointer;
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}
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LEMuSRMuonDecayChannel::~LEMuSRMuonDecayChannel()
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{
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}
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G4DecayProducts *LEMuSRMuonDecayChannel::DecayItPolarized(G4double mass,G4ThreeVector polar)
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{
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SetParentPolarization(polar);
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#ifdef G4VERBOSE
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if (GetVerboseLevel()>2) {
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G4cout << "LEMuSRMuonDecayChannel:: theParentPolarization is" <<theParentPolarization <<G4endl;
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}
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#endif
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return DecayIt(mass);
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}
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G4DecayProducts *LEMuSRMuonDecayChannel::DecayIt(G4double)
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{
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if(theParentPolarization == G4ThreeVector(0,0,0))
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{
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// Generate random theParentPolarization direction
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G4double cost = 1. - 2.*G4UniformRand();
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G4double sint = std::sqrt((1.-cost)*(1.+cost));
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G4double phi = twopi*G4UniformRand();
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G4double sinp = std::sin(phi);
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G4double cosp = std::cos(phi);
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G4double px = sint*cosp;
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G4double py = sint*sinp;
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G4double pz = cost;
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theParentPolarization.setX(px);
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theParentPolarization.setY(py);
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theParentPolarization.setZ(pz);
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}
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// assumes the pure V-A coupling
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// gives incorrect energy spectrum for neutrinos
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#ifdef G4VERBOSE
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if (GetVerboseLevel()>2) {
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G4cout << "LEMuSRMuonDecayChannel::DecayIt ";
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}
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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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//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 Positron energy
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G4double daughtermomentum[3];
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G4double energy;
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G4double x; // maximal positron energy is 52.831MeV
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G4double r;
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do {
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do {
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r = G4UniformRand();
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x = G4UniformRand();
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} while (r > (3.0 - 2.0*x)*x*x);
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energy = x*52.831*MeV;
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} while (energy <0.0|| energy > 52.831);
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// Anglular Distribution
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G4double energymax=52.831*MeV;
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G4double E=energy/energymax;
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G4double D = (2*E-1)/(3-2*E);
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// theta
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G4double K = G4UniformRand();
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costheta = 1/D*(-1.+ sqrt(1.-2*D*(2*K-1)+D*D));
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theta = acos(costheta);
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sintheta=sin(theta);
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// phi
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phi = 2.0*M_PI*G4UniformRand()*rad;
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sinphi = sin(phi);
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cosphi = cos(phi);
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// rotation angles
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G4double px = sintheta*sinphi;
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G4double py = sintheta*cosphi;
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G4double pz = costheta;
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G4ThreeVector direction0(px,py,pz);
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direction0.rotateUz(theParentPolarization);
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#ifdef G4VERBOSE
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if (GetVerboseLevel()>2) {
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G4cout << "LEMuSRMuonDecayChanel::DecayIt \n";
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G4cout <<"e+ momentum direction: " << direction0 <<G4endl;
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G4cout <<"energy: " <<energy <<G4endl;
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}
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#endif
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daughtermomentum[0] = sqrt(energy*energy + 2.0*energy* daughtermass[0]);
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G4DynamicParticle * daughterparticle
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= new G4DynamicParticle( daughters[0], direction0*daughtermomentum[0]);
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daughterparticle->SetPolarization(theParentPolarization.x(),theParentPolarization.y(),theParentPolarization.z());
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products->PushProducts(daughterparticle);
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// daughter 1 ,2 (neutrinos)
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// create neutrinos in the C.M frame of two neutrinos
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G4double energy2 = parentmass*(1.0 - x/2.0);
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G4double vmass = sqrt((energy2-daughtermomentum[0])*(energy2+daughtermomentum[0]));
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G4double beta = -1.0*daughtermomentum[0]/energy2;
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G4double costhetan = 2.*G4UniformRand()-1.0;
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G4double sinthetan = sqrt((1.0-costhetan)*(1.0+costhetan));
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G4double phin = 2.0*M_PI*G4UniformRand()*rad;
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G4double sinphin = sin(phin);
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G4double cosphin = cos(phin);
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G4ThreeVector direction1(sinthetan*cosphin,sinthetan*sinphin,costhetan);
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G4DynamicParticle * daughterparticle1
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= new G4DynamicParticle( daughters[1], direction1*(vmass/2.));
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G4DynamicParticle * daughterparticle2
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= new G4DynamicParticle( daughters[2], direction1*(-1.0*vmass/2.));
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// boost to the muon rest frame
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G4LorentzVector p4;
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p4 = daughterparticle1->Get4Momentum();
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p4.boost( direction0.x()*beta, direction0.y()*beta, direction0.z()*beta);
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daughterparticle1->Set4Momentum(p4);
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p4 = daughterparticle2->Get4Momentum();
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p4.boost( direction0.x()*beta, direction0.y()*beta, direction0.z()*beta);
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daughterparticle2->Set4Momentum(p4);
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products->PushProducts(daughterparticle1);
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products->PushProducts(daughterparticle2);
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daughtermomentum[1] = daughterparticle1->GetTotalMomentum();
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daughtermomentum[2] = daughterparticle2->GetTotalMomentum();
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// output message
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#ifdef G4VERBOSE
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if (GetVerboseLevel()>2) {
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G4cout << "LEMuSRMuonDecayChanel::DecayIt ";
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G4cout << " THETA aNGLE ::" <<theta <<G4endl;
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G4cout << " PHI aNGLE ::" <<phi <<G4endl;
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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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