Gabriele Cosmo
95 lines
3.4 KiB
C++
95 lines
3.4 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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// $Id: G4DNAEmfietzoglouAngularDistributionPolicy.cc,v 1.3 2006/06/29 19:39:22 gunter Exp $
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// GEANT4 tag $Name: geant4-08-01 $
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#include "G4DNAEmfietzoglouAngularDistributionPolicy.hh"
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#include "Randomize.hh"
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G4double G4DNAEmfietzoglouAngularDistributionPolicy :: RandomizeCosTheta(G4double k, G4int z) const
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{
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// d sigma_el sigma_Ruth(K)
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// ------------ (K) ~ -----------------------------
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// d Omega (1 + 2 n(K) - std::cos(theta))^2
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//
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// We extract std::cos(theta) distributed as (1 + 2 n(K) - std::cos(theta))^-2
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//
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// Maximum is for theta=0: 1/(4 n(K)^2) (When n(K) is positive, that is always satisfied within the validity of the process)
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//
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// Phys. Med. Biol. 45 (2000) 3171-3194
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G4double n;
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n=ScreeningFactor(k, z);
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G4double oneOverMax;
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oneOverMax=(4.*n*n);
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G4double cosTheta;
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G4double fCosTheta;
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do
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{
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cosTheta = 2.*G4UniformRand()-1.;
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fCosTheta = (1 + 2.*n - cosTheta);
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fCosTheta = oneOverMax/(fCosTheta*fCosTheta);
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}
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while (fCosTheta < G4UniformRand());
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return cosTheta;
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}
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G4double G4DNAEmfietzoglouAngularDistributionPolicy :: ScreeningFactor(G4double k, G4int z) const
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{
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//
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// alpha_1 + beta_1 ln(K/eV) constK Z^(2/3)
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// n(T) = -------------------------- -----------------
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// K/(m_e c^2) 2 + K/(m_e c^2)
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//
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// Where K is the electron non-relativistic kinetic energy
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//
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// n(T) > 0 for T < ~ 400 MeV
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//
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// Nucl. Instr. Meth. 155 (1978) 145-156
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const G4double alpha_1(1.64);
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const G4double beta_1(-0.0825);
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const G4double constK(1.7E-5);
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G4double numerator;
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numerator=(alpha_1+beta_1*std::log(k/eV))*constK*std::pow(static_cast<double>(z), 2./3.);
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k/=electron_mass_c2;
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G4double denominator;
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denominator=k*(2+k);
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return numerator/denominator;
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}
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