Gabriele Cosmo
152 lines
5.8 KiB
C++
152 lines
5.8 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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//
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// -------------------------------------------------------------------
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//
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// GEANT4 Class file
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//
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//
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// File name: G4DipBustGenerator
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//
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// Author: Vladimir Grichine
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//
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// Creation date: 17 May 2011
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//
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// Modifications:
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//
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// 17.07.2018 optimisations, using G4Pow in SampleCosTheta() method M.Novak
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//
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// Class Description:
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//
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// Bremsstrahlung Angular Distribution Generation
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// suggested the dipole approximation in the rest frame of electron
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// busted in the laboratory frame.
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//
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// Class Description: End
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//
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// -------------------------------------------------------------------
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//
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#include "G4DipBustGenerator.hh"
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#include "Randomize.hh"
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// #include "G4Log.hh"
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// #include "G4Exp.hh"
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#include "G4Pow.hh"
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#include <CLHEP/Units/PhysicalConstants.h>
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4DipBustGenerator::G4DipBustGenerator(const G4String&)
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: G4VEmAngularDistribution("DipBustGen")
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{}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4DipBustGenerator::~G4DipBustGenerator() = default;
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double G4DipBustGenerator::SampleCosTheta(const G4double kinEnergy)
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{
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const G4double c = 4. - 8.*G4UniformRand();
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const G4double delta = 0.5*(std::sqrt(c*c+4.) + std::abs(c));
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const G4double signc = (c < 0.) ? -1.0 : 1.0;
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// const G4double cofA = -signc*G4Exp(G4Log(delta)/3.0);
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const G4double cofA = -signc*G4Pow::GetInstance()->A13(delta);
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const G4double cosTheta = std::min(1.,std::max(-1.,cofA - 1./cofA));
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const G4double tau = kinEnergy/CLHEP::electron_mass_c2;
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const G4double beta = std::sqrt(tau*(tau + 2.))/(tau + 1.);
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return (cosTheta + beta)/(1. + cosTheta*beta);
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4ThreeVector&
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G4DipBustGenerator::SampleDirection(const G4DynamicParticle* dp, G4double,
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G4int, const G4Material*)
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{
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const G4double cosTheta = SampleCosTheta(dp->GetKineticEnergy());
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const G4double sinTheta = std::sqrt((1. - cosTheta)*(1. + cosTheta));
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const G4double phi = CLHEP::twopi*G4UniformRand();
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fLocalDirection.set(sinTheta*std::cos(phi), sinTheta*std::sin(phi),cosTheta);
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fLocalDirection.rotateUz(dp->GetMomentumDirection());
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return fLocalDirection;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double G4DipBustGenerator::PolarAngle(G4double eTkin,
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G4double, // final_energy
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G4int ) // Z
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{
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const G4double cosTheta = SampleCosTheta(eTkin);
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G4double theta = std::acos(cosTheta);
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theta = std::min(std::max(theta, 0.), CLHEP::pi);
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return theta;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4DipBustGenerator::SamplePairDirections(const G4DynamicParticle* dp,
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G4double elecKinEnergy,
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G4double posiKinEnergy,
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G4ThreeVector& dirElectron,
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G4ThreeVector& dirPositron,
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G4int, const G4Material*)
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{
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const G4double phi = CLHEP::twopi * G4UniformRand();
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const G4double sinp = std::sin(phi);
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const G4double cosp = std::cos(phi);
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G4double cost = SampleCosTheta(elecKinEnergy);
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G4double sint = std::sqrt((1. - cost)*(1. + cost));
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dirElectron.set(sint*cosp, sint*sinp, cost);
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dirElectron.rotateUz(dp->GetMomentumDirection());
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cost = SampleCosTheta(posiKinEnergy);
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sint = std::sqrt((1. - cost)*(1. + cost));
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dirPositron.set(-sint*cosp, -sint*sinp, cost);
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dirPositron.rotateUz(dp->GetMomentumDirection());
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4DipBustGenerator::PrintGeneratorInformation() const
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{
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G4cout << "\n" << G4endl;
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G4cout << "Angular Generator based on classical formula from" << G4endl;
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G4cout << "J.D. Jackson, Classical Electrodynamics, Wiley, New York 1975"
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<< G4endl;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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