Gabriele Cosmo
113 lines
4.0 KiB
C++
113 lines
4.0 KiB
C++
//
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// ********************************************************************
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// * DISCLAIMER *
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// * *
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// * The following disclaimer summarizes all the specific disclaimers *
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// * of contributors to this software. The specific disclaimers,which *
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// * govern, are listed with their locations in: *
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// * http://cern.ch/geant4/license *
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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. *
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// * *
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// * This code implementation is the intellectual property of the *
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// * GEANT4 collaboration. *
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// * By copying, distributing or modifying the Program (or any work *
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// * based on the Program) you indicate your acceptance of this *
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// * statement, and all its terms. *
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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: G4BohrFluctuations
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//
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// Author: Vladimir Ivanchenko
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//
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// Creation date: 02.04.2003
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//
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// Modifications:
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//
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//
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// Class Description: Sampling of Gaussion fluctuations
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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 "G4BohrFluctuations.hh"
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#include "Randomize.hh"
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#include "G4Poisson.hh"
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#include "G4ParticleDefinition.hh"
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4BohrFluctuations::G4BohrFluctuations(const G4String& nam)
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:G4VEmFluctuationModel(nam),
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minNumberInteractionsBohr(10.0),
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minFraction(0.2)
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{}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4BohrFluctuations::~G4BohrFluctuations()
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{}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4BohrFluctuations::Initialise(const G4ParticleDefinition* part)
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{
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particle = part;
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particleMass = part->GetPDGMass();
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G4double q = part->GetPDGCharge()/eplus;
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chargeSquare = q*q;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double G4BohrFluctuations::SampleFluctuations(const G4Material* material,
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const G4DynamicParticle* dp,
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G4double& tmax,
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G4double& length,
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G4double& meanLoss)
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{
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G4double siga = Dispersion(material,dp,tmax,length);
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G4double loss = meanLoss;
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// Gaussian fluctuation
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if (meanLoss >= minNumberInteractionsBohr*tmax) {
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// Increase fluctuations for big fractional energy loss
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if ( meanLoss > minFraction*kineticEnergy ) {
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G4double gam = (kineticEnergy - meanLoss)/particleMass + 1.0;
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G4double b2 = 1.0 - 1.0/(gam*gam);
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G4double x = b2/beta2;
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G4double x3 = 1.0/(x*x*x);
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siga *= 0.25*(1.0 + x)*(x3 + (1.0/b2 - 0.5)/(1.0/beta2 - 0.5) );
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}
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siga = sqrt(siga);
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do {
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loss = G4RandGauss::shoot(meanLoss,siga);
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} while (loss < 0. || loss > 2.*meanLoss);
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// Poisson fluctuations
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} else {
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G4double navr = meanLoss*meanLoss/siga;
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G4double n = (G4double)G4Poisson(navr);
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loss = meanLoss*n/navr;
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}
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return loss;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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