Gabriele Cosmo
241 lines
7.7 KiB
C++
241 lines
7.7 KiB
C++
//
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// ********************************************************************
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// * License and Disclaimer *
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// * *
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// * The Geant4 software is copyright of the Copyright Holders of *
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// * the Geant4 Collaboration. It is provided under the terms and *
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// * conditions of the Geant4 Software License, included in the file *
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// * LICENSE and available at http://cern.ch/geant4/license . These *
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// * include a list of copyright holders. *
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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. Please see the license in the file LICENSE and URL above *
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// * for the full disclaimer and the limitation of liability. *
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// * *
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// * This code implementation is the result of the scientific and *
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// * technical work of the GEANT4 collaboration. *
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// * By using, copying, modifying or distributing the software (or *
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// * any work based on the software) you agree to acknowledge its *
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// * use in resulting scientific publications, and indicate your *
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// * acceptance of all terms of the Geant4 Software license. *
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// ********************************************************************
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//
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// G4PionRadiativeDecayChannel class implementation
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// GEANT 4 class header file
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//
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// Author: P.Gumplinger, 30 July 2007
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// Reference: M. Blecher, TRIUMF/PIENU Technote
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// "Inclusion of pi->enug in the Monte Carlo"
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// --------------------------------------------------------------------
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#include "G4PionRadiativeDecayChannel.hh"
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#include "G4DecayProducts.hh"
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#include "G4LorentzVector.hh"
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#include "G4PhysicalConstants.hh"
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#include "G4SystemOfUnits.hh"
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#include "Randomize.hh"
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namespace
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{
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const G4double beta = 3.6612e-03;
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const G4double cib = 1.16141e-03;
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const G4double csdp = 3.45055e-02;
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const G4double csdm = 5.14122e-03;
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const G4double cif = 4.63543e-05;
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const G4double cig = 1.78928e-05;
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const G4double xl = 2. * 0.1 * MeV / 139.57 * MeV;
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const G4double yl = ((1. - xl) + std::sqrt((1 - xl) * (1 - xl) + 4 * beta * beta)) / 2.;
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const G4double xu = 1. - (yl - std::sqrt(yl * yl - 4. * beta * beta)) / 2.;
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const G4double yu = 1. + beta * beta;
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inline G4double D2W(const G4double x, const G4double y)
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{
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return cib * (1. - y) * (1. + ((1. - x) * (1. - x))) / ((x * x) * (x + y - 1.))
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+ csdp * (1. - x) * ((x + y - 1.) * (x + y - 1.)) + csdm * (1. - x) * ((1. - y) * (1. - y))
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+ cif * (x - 1.) * (1. - y) / x + cig * (1. - y) * (1. - x + (x * x) / (x + y - 1.)) / x;
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}
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const G4double d2wmax = D2W(xl, yl);
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} // namespace
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G4PionRadiativeDecayChannel::G4PionRadiativeDecayChannel(const G4String& theParentName,
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G4double theBR)
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: G4VDecayChannel("Radiative Pion Decay", 1)
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{
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// set names for daughter particles
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if (theParentName == "pi+") {
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SetBR(theBR);
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SetParent("pi+");
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SetNumberOfDaughters(3);
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SetDaughter(0, "e+");
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SetDaughter(1, "gamma");
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SetDaughter(2, "nu_e");
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}
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else if (theParentName == "pi-") {
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SetBR(theBR);
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SetParent("pi-");
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SetNumberOfDaughters(3);
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SetDaughter(0, "e-");
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SetDaughter(1, "gamma");
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SetDaughter(2, "anti_nu_e");
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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 << "G4RadiativePionDecayChannel::G4PionRadiativeDecayChannel()" << G4endl;
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G4cout << "Parent particle is not charged pion: ";
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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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G4PionRadiativeDecayChannel&
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G4PionRadiativeDecayChannel::operator=(const G4PionRadiativeDecayChannel& right)
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{
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if (this != &right) {
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kinematics_name = right.kinematics_name;
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verboseLevel = right.verboseLevel;
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rbranch = right.rbranch;
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// copy parent name
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parent_name = new G4String(*right.parent_name);
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// clear daughters_name array
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ClearDaughtersName();
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// recreate array
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numberOfDaughters = right.numberOfDaughters;
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if (numberOfDaughters > 0) {
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if (daughters_name != nullptr) ClearDaughtersName();
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daughters_name = new G4String*[numberOfDaughters];
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// copy daughters name
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for (G4int index = 0; index < numberOfDaughters; ++index) {
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daughters_name[index] = new G4String(*right.daughters_name[index]);
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}
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}
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}
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return *this;
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}
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G4DecayProducts* G4PionRadiativeDecayChannel::DecayIt(G4double)
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{
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#ifdef G4VERBOSE
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if (GetVerboseLevel() > 1) G4cout << "G4PionRadiativeDecayChannel::DecayIt ";
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#endif
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CheckAndFillParent();
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CheckAndFillDaughters();
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// parent mass
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G4double parentmass = G4MT_parent->GetPDGMass();
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G4double EMPI = parentmass;
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// daughters'mass
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const G4int N_DAUGHTER = 3;
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G4double daughtermass[N_DAUGHTER];
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// G4double sumofdaughtermass = 0.0;
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for (G4int index = 0; index < N_DAUGHTER; ++index) {
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daughtermass[index] = G4MT_daughters[index]->GetPDGMass();
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// sumofdaughtermass += daughtermass[index];
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}
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G4double EMASS = daughtermass[0];
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// create parent G4DynamicParticle at rest
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G4ThreeVector dummy;
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auto parentparticle = new G4DynamicParticle(G4MT_parent, dummy, 0.0);
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// create G4Decayproducts
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auto products = new G4DecayProducts(*parentparticle);
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delete parentparticle;
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G4double x, y;
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const std::size_t MAX_LOOP = 1000;
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for (std::size_t loop_counter1 = 0; loop_counter1 < MAX_LOOP; ++loop_counter1) {
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for (std::size_t loop_counter2 = 0; loop_counter2 < MAX_LOOP; ++loop_counter2) {
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x = xl + G4UniformRand() * (xu - xl);
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y = yl + G4UniformRand() * (yu - yl);
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if (x + y > 1.) break;
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}
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G4double d2w = D2W(x, y);
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if (d2w > G4UniformRand() * d2wmax) break;
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}
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// Calculate the angle between positron and photon (cosine)
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//
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G4double cthetaGE =
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(y * (x - 2.) + 2. * (1. - x + beta * beta)) / (x * std::sqrt(y * y - 4. * beta * beta));
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G4double G = x * EMPI / 2.;
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G4double E = y * EMPI / 2.;
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if (E < EMASS) E = EMASS;
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// calculate daughter momentum
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G4double daughtermomentum[2];
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daughtermomentum[0] = std::sqrt(E * E - EMASS * EMASS);
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G4double cthetaE = 2. * G4UniformRand() - 1.;
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G4double sthetaE = std::sqrt(1. - cthetaE * cthetaE);
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G4double phiE = twopi * G4UniformRand() * rad;
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G4double cphiE = std::cos(phiE);
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G4double sphiE = std::sin(phiE);
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// Coordinates of the decay positron
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//
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G4double px = sthetaE * cphiE;
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G4double py = sthetaE * sphiE;
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G4double pz = cthetaE;
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G4ThreeVector direction0(px, py, pz);
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auto daughterparticle0 =
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new G4DynamicParticle(G4MT_daughters[0], daughtermomentum[0] * direction0);
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products->PushProducts(daughterparticle0);
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daughtermomentum[1] = G;
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G4double sthetaGE = std::sqrt(1. - cthetaGE * cthetaGE);
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G4double phiGE = twopi * G4UniformRand() * rad;
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G4double cphiGE = std::cos(phiGE);
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G4double sphiGE = std::sin(phiGE);
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// Coordinates of the decay gamma with respect to the decay positron
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//
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px = sthetaGE * cphiGE;
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py = sthetaGE * sphiGE;
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pz = cthetaGE;
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G4ThreeVector direction1(px, py, pz);
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direction1.rotateUz(direction0);
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auto daughterparticle1 =
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new G4DynamicParticle(G4MT_daughters[1], daughtermomentum[1] * direction1);
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products->PushProducts(daughterparticle1);
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// output message
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#ifdef G4VERBOSE
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if (GetVerboseLevel() > 1) {
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G4cout << "G4PionRadiativeDecayChannel::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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