Gabriele Cosmo
252 lines
8.5 KiB
C++
252 lines
8.5 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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// $Id: G4PolarizedComptonCrossSection.cc 96114 2016-03-16 18:51:33Z gcosmo $
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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: G4PolarizedComptonCrossSection
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//
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// Author: Andreas Schaelicke
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//
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// Creation date: 15.05.2005
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//
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// Modifications:
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//
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// Class Description:
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// determine the polarization of the final state
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// in a Compton scattering process employing the differential
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// cross section by F.W.Lipps & H.A.Tolhoek
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// ( Physica 20 (1954) 395 )
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// recalculated by P.Starovoitov
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//
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#include "G4PolarizedComptonCrossSection.hh"
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#include "G4PhysicalConstants.hh"
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#include "Randomize.hh"
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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G4PolarizedComptonCrossSection::G4PolarizedComptonCrossSection()
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: gammaPol2(false), electronPol3(false)
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{
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SetYmin(0.);
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// G4cout<<"G4PolarizedComptonCrossSection() init\n";
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re2 = classic_electr_radius * classic_electr_radius * sqr(4*pi/hbarc);
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// G4double unit_conversion = hbarc_squared ;
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// G4cout<<" (keV)^2* m^2 ="<<unit_conversion<<"\n";
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phi0 = 0.; polXS = 0.; unpXS = 0.;
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phi2 = G4ThreeVector(0., 0., 0.);
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phi3 = G4ThreeVector(0., 0., 0.);
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polxx = polyy = polzz = polxz = polzx = polyz = polzy = polxy = polyx = 0.;
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diffXSFactor = 1.;
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totalXSFactor = 1.;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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G4PolarizedComptonCrossSection::~G4PolarizedComptonCrossSection()
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{}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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void G4PolarizedComptonCrossSection::Initialize(G4double eps, G4double X, G4double , // phi
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const G4StokesVector & pol0,
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const G4StokesVector & pol1,
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G4int flag)
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{
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G4double cosT = 1. - (1./eps - 1.)/X;
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if(cosT > 1.+1.e-8) cosT = 1.;
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if(cosT < -1.-1.e-8) cosT = -1.;
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G4double cosT2 = cosT*cosT;
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G4double cosT3 = cosT2*cosT;
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G4double sinT2 = 1. - cosT2;
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if(sinT2 > 1. + 1.e-8) sinT2 = 1.;
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if(sinT2 < 0.) sinT2 = 0.;
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G4double sinT = std::sqrt(sinT2);
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G4double cos2T = 2.*cosT2 - 1.;
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G4double sin2T = 2.*sinT*cosT;
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G4double eps2 = sqr(eps);
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DefineCoefficients(pol0,pol1);
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diffXSFactor = re2/(4.*X);
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// unpolarized Cross Section
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unpXS = (eps2 + 1. - eps*sinT2)/(2.*eps);
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// initial polarization dependence
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polXS = -sinT2*pol0.x() + (1. - eps)*sinT*polzx + ((eps2 - 1.)/eps)*cosT*polzz;
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polXS *= 0.5;
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phi0 = unpXS + polXS;
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if (flag == 2 ){
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// polarization of outgoing photon
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G4double PHI21 = -sinT2 + 0.5*(cos2T + 3.)*pol0.x() - ((1. - eps)/eps)*sinT*polzx;
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PHI21 *= 0.5;
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G4double PHI22 = cosT*pol0.y() + ((1. - eps)/(2.*eps))*sinT*polzy;
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G4double PHI23 = ((eps2 + 1.)/eps)*cosT*pol0.z() - ((1. - eps)/eps)*(eps*cosT2 + 1.)*pol1.z();
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PHI23 += 0.5*(1. - eps)*sin2T*pol1.x();
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PHI23 += (eps - 1.)*(-sinT2*polxz + sinT*polyy - 0.5*sin2T*polxx);
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PHI23 *= 0.5;
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phi2 = G4ThreeVector(PHI21, PHI22, PHI23);
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// polarization of outgoing electron
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G4double PHI32 = -sinT2*polxy + ((1. - eps)/eps)*sinT*polyz + 0.5*(cos2T + 3.)*pol1.y();
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PHI32 *= 0.5;
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G4double PHI31 = 0., PHI31add = 0., PHI33 = 0., PHI33add = 0.;
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if ((1. - eps) > 1.e-12){
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G4double helpVar = std::sqrt(eps2 - 2.*cosT*eps + 1.);
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PHI31 = (1. - eps)*(1. + cosT)*sinT*pol0.z();
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PHI31 += (-eps*cosT3 + eps*cosT2 + (eps - 2.)*cosT + eps)*pol1.x();
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PHI31 += -(eps*cosT2 - eps*cosT + cosT + 1.)*sinT*pol1.z();
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PHI31 /= 2.*helpVar;
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PHI31add = -eps*sqr(1. - cosT)*(1. + cosT)*polxx;
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PHI31add += (1. - eps)*sinT2*polyy;
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PHI31add += -(-eps2 + cosT*(cosT*eps - eps + 1.)*eps + eps - 1.)*sinT*polxz/eps;
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PHI31add /= 2.*helpVar;
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PHI33 = ((1. - eps)/eps)*(-eps*cosT2 + eps*(eps + 1.)*cosT - 1.)*pol0.z();
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PHI33 += -(eps*cosT2 + (1. - eps)*eps*cosT + 1.)*sinT*pol1.x();
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PHI33 += -(-eps2*cosT3 + eps*(eps2 - eps + 1.)*cosT2 - cosT + eps2)*pol1.z()/eps;
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PHI33 /= -2.*helpVar;
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PHI33add = (eps*(eps - cosT - 1.)*cosT + 1.)*sinT*polxx;
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PHI33add += -(-eps2 + cosT*eps + eps - 1.)*sinT2*polxz;
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PHI33add += (eps - 1.)*(cosT - eps)*sinT*polyy;
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PHI33add /= -2.*helpVar;
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}else{
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PHI31 = -pol1.z() - (X - 1.)*std::sqrt(1. - eps)*pol1.x()/std::sqrt(2.*X);
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PHI31add = -(-X*X*pol1.z() - 2.*X*(2.*pol0.z() - pol1.z()) - (4.*pol0.x() + 5.)*pol1.z())*(1. - eps)/(4.*X);
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PHI33 = pol1.x() - (X - 1.)*std::sqrt(1. - eps)*pol1.z()/std::sqrt(2.*X);
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PHI33add = -(X*X - 2.*X + 4.*pol0.x() + 5.)*(1. - eps)*pol1.x()/(4.*X);
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}
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phi3 = G4ThreeVector(PHI31 + PHI31add, PHI32, PHI33 + PHI33add);
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}
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unpXS *= diffXSFactor;
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polXS *= diffXSFactor;
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phi0 *= diffXSFactor;
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phi2 *= diffXSFactor;
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phi3 *= diffXSFactor;
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}
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G4double G4PolarizedComptonCrossSection::XSection(const G4StokesVector & pol2,const G4StokesVector & pol3)
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{
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gammaPol2 = !(pol2==G4StokesVector::ZERO);
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electronPol3 = !(pol3==G4StokesVector::ZERO);
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G4double phi = 0.;
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// polarization independent part
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phi += phi0;
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if (gammaPol2) {
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// part depending on the polarization of the final photon
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phi += phi2*pol2;
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}
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if (electronPol3) {
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// part depending on the polarization of the final electron
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phi += phi3*pol3;
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}
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// return cross section.
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return phi;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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G4double G4PolarizedComptonCrossSection::TotalXSection(G4double /*xmin*/, G4double /*xmax*/, G4double k0,
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const G4StokesVector & pol0,
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const G4StokesVector & pol1)
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{
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// G4double k0 = gammaEnergy / electron_mass_c2 ;
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G4double k1 = 1. + 2.*k0 ;
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// // pi*re^2
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// G4double re=2.81794e-15; //m
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// G4double barn=1.e-28; //m^2
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G4double Z=theZ;
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G4double unit = Z*pi*classic_electr_radius
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* classic_electr_radius ; // *1./barn;
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G4double pre = unit/(sqr(k0)*sqr(1.+2.*k0));
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G4double xs_0 = ((k0 - 2.)*k0 -2.)*sqr(k1)*std::log(k1) + 2.*k0*(k0*(k0 + 1.)*(k0 + 8.) + 2.);
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G4double xs_pol = (k0 + 1.)*sqr(k1)*std::log(k1) - 2.*k0*(5.*sqr(k0) + 4.*k0 + 1.);
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return pre*(xs_0/k0 + pol0.p3()*pol1.z()*xs_pol);
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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G4StokesVector G4PolarizedComptonCrossSection::GetPol2()
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{
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// Note, mean polarization can not contain correlation
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// effects.
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return 1./phi0 * phi2;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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G4StokesVector G4PolarizedComptonCrossSection::GetPol3()
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{
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// Note, mean polarization can not contain correlation
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// effects.
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return 1./phi0 * phi3;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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void G4PolarizedComptonCrossSection::DefineCoefficients(const G4StokesVector & pol0,
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const G4StokesVector & pol1)
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{
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polxx=pol0.x()*pol1.x();
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polyy=pol0.y()*pol1.y();
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polzz=pol0.z()*pol1.z();
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polxz=pol0.x()*pol1.z();
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polzx=pol0.z()*pol1.x();
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polyz=pol0.y()*pol1.z();
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polzy=pol0.z()*pol1.y();
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polxy=pol0.x()*pol1.y();
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polyx=pol0.y()*pol1.x();
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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