Gabriele Cosmo
180 lines
6.0 KiB
C++
180 lines
6.0 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: G4hPairProductionModel.cc 74020 2013-09-19 13:38:38Z gcosmo $
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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: G4hPairProductionModel
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//
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// Author: Vladimir Ivanchenko on base of G4MuPairProductionModel
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//
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// Creation date: 28.02.2008
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//
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// Modifications:
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//
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//
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// Class Description:
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//
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//
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// -------------------------------------------------------------------
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//
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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#include "G4hPairProductionModel.hh"
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#include "G4PhysicalConstants.hh"
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#include "G4Log.hh"
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#include "G4Exp.hh"
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using namespace std;
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G4hPairProductionModel::G4hPairProductionModel(const G4ParticleDefinition* p,
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const G4String& nam)
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: G4MuPairProductionModel(p, nam)
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{}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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G4hPairProductionModel::~G4hPairProductionModel()
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{}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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G4double G4hPairProductionModel::ComputeDMicroscopicCrossSection(
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G4double tkin,
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G4double Z,
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G4double pairEnergy)
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// differential cross section
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{
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static const G4double bbbtf= 183. ;
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static const G4double bbbh = 202.4 ;
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static const G4double g1tf = 1.95e-5 ;
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static const G4double g2tf = 5.3e-5 ;
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static const G4double g1h = 4.4e-5 ;
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static const G4double g2h = 4.8e-5 ;
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G4double totalEnergy = tkin + particleMass;
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G4double residEnergy = totalEnergy - pairEnergy;
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G4double massratio = particleMass/electron_mass_c2 ;
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G4double massratio2 = massratio*massratio ;
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G4double cross = 0.;
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G4double c3 = 0.75*sqrte*particleMass;
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if (residEnergy <= c3*z13) { return cross; }
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G4double c7 = 4.*CLHEP::electron_mass_c2;
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G4double c8 = 6.*particleMass*particleMass;
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G4double alf = c7/pairEnergy;
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G4double a3 = 1. - alf;
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if (a3 <= 0.) { return cross; }
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// zeta calculation
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G4double bbb,g1,g2;
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if( Z < 1.5 ) { bbb = bbbh ; g1 = g1h ; g2 = g2h ; }
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else { bbb = bbbtf; g1 = g1tf; g2 = g2tf; }
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G4double zeta = 0;
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G4double zeta1 =
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0.073*G4Log(totalEnergy/(particleMass+g1*z23*totalEnergy))-0.26;
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if ( zeta1 > 0.)
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{
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G4double zeta2 =
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0.058*G4Log(totalEnergy/(particleMass+g2*z13*totalEnergy))-0.14;
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zeta = zeta1/zeta2 ;
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}
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G4double z2 = Z*(Z+zeta);
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G4double screen0 = 2.*electron_mass_c2*sqrte*bbb/(z13*pairEnergy);
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G4double a0 = totalEnergy*residEnergy;
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G4double a1 = pairEnergy*pairEnergy/a0;
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G4double bet = 0.5*a1;
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G4double xi0 = 0.25*massratio2*a1;
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G4double del = c8/a0;
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G4double rta3 = sqrt(a3);
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G4double tmnexp = alf/(1. + rta3) + del*rta3;
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if(tmnexp >= 1.0) { return cross; }
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G4double tmn = G4Log(tmnexp);
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G4double sum = 0.;
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// Gaussian integration in ln(1-ro) ( with 8 points)
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for (G4int i=0; i<8; i++)
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{
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G4double a4 = G4Exp(tmn*xgi[i]); // a4 = (1.-asymmetry)
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G4double a5 = a4*(2.-a4) ;
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G4double a6 = 1.-a5 ;
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G4double a7 = 1.+a6 ;
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G4double a9 = 3.+a6 ;
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G4double xi = xi0*a5 ;
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G4double xii = 1./xi ;
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G4double xi1 = 1.+xi ;
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G4double screen = screen0*xi1/a5 ;
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G4double yeu = 5.-a6+4.*bet*a7 ;
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G4double yed = 2.*(1.+3.*bet)*G4Log(3.+xii)-a6-a1*(2.-a6) ;
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G4double ye1 = 1.+yeu/yed ;
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G4double ale=G4Log(bbb/z13*sqrt(xi1*ye1)/(1.+screen*ye1)) ;
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G4double cre = 0.5*G4Log(1.+2.25*z23*xi1*ye1/massratio2) ;
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G4double be;
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if (xi <= 1.e3) {
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be = ((2.+a6)*(1.+bet)+xi*a9)*G4Log(1.+xii)+(a5-bet)/xi1-a9;
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} else {
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be = (3.-a6+a1*a7)/(2.*xi);
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}
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G4double fe = (ale-cre)*be;
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if ( fe < 0.) { fe = 0.; }
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G4double ymu = 4.+a6 +3.*bet*a7 ;
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G4double ymd = a7*(1.5+a1)*G4Log(3.+xi)+1.-1.5*a6 ;
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G4double ym1 = 1.+ymu/ymd ;
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G4double alm_crm = G4Log(bbb*massratio/(1.5*z23*(1.+screen*ym1)));
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G4double a10,bm;
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if ( xi >= 1.e-3)
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{
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a10 = (1.+a1)*a5 ;
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bm = (a7*(1.+1.5*bet)-a10*xii)*G4Log(xi1)+xi*(a5-bet)/xi1+a10;
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} else {
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bm = (5.-a6+bet*a9)*(xi/2.);
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}
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G4double fm = alm_crm*bm;
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if ( fm < 0.) { fm = 0.; }
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sum += wgi[i]*a4*(fe+fm/massratio2);
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}
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cross = -tmn*sum*factorForCross*z2*residEnergy/(totalEnergy*pairEnergy);
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return cross;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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