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75c7fd177dc4853b8a93aaedc78d6037aa36dba6
geant4/source/processes/electromagnetic/standard/src/G4MscModel71.cc
T
Gabriele Cosmo fe73f43734 Import Geant4 8.2.0 source tree
2016-06-09 14:55:03 +02:00

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//
// ********************************************************************
// * License and Disclaimer *
// * *
// * The Geant4 software is copyright of the Copyright Holders of *
// * the Geant4 Collaboration. It is provided under the terms and *
// * conditions of the Geant4 Software License, included in the file *
// * LICENSE and available at http://cern.ch/geant4/license . These *
// * include a list of copyright holders. *
// * *
// * Neither the authors of this software system, nor their employing *
// * institutes,nor the agencies providing financial support for this *
// * work make any representation or warranty, express or implied, *
// * regarding this software system or assume any liability for its *
// * use. Please see the license in the file LICENSE and URL above *
// * for the full disclaimer and the limitation of liability. *
// * *
// * This code implementation is the result of the scientific and *
// * technical work of the GEANT4 collaboration. *
// * By using, copying, modifying or distributing the software (or *
// * any work based on the software) you agree to acknowledge its *
// * use in resulting scientific publications, and indicate your *
// * acceptance of all terms of the Geant4 Software license. *
// ********************************************************************
//
// $Id: G4MscModel71.cc,v 1.4 2006/06/29 19:53:08 gunter Exp $
// GEANT4 tag $Name: geant4-08-02 $
//
// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name: G4MscModel71
//
// Author: Laszlo Urban
//
// Creation date: 03.03.2001
//
// Modifications:
//
// 27-03-03 Move model part from G4MultipleScattering (V.Ivanchenko)
// 23-05-03 important change in angle distribution for muons/hadrons
// the central part now is similar to the Highland parametrization +
// minor correction in angle sampling algorithm (for all particles)
// (L.Urban)
// 30-05-03 misprint in SampleCosineTheta corrected(L.Urban)
// 27-03-03 Rename (V.Ivanchenko)
// 05-08-03 angle distribution has been modified (L.Urban)
// 06-11-03 precision problems solved for high energy (PeV) particles
// change in the tail of the angular distribution
// highKinEnergy is set to 100 PeV (L.Urban)
//
// 10-11-03 highKinEnergy is set back to 100 TeV, some tail tuning +
// cleaning (L.Urban)
// 26-11-03 correction in TrueStepLength :
// trueLength <= currentRange (L.Urban)
// 01-03-04 signature changed in SampleCosineTheta,
// energy dependence calculations has been simplified,
// 11-03-04 corrections in GeomPathLength,TrueStepLength,
// SampleCosineTheta
// 23-04-04 true -> geom and geom -> true transformation has been
// rewritten, changes in the angular distribution (L.Urban)
// 19-07-04 correction in SampleCosineTheta in order to avoid
// num. precision problems at high energy/small step(L.Urban)
// 17-08-04 changes in the angle distribution (slightly modified
// Highland formula for the width of the central part,
// changes in the numerical values of some other parameters)
// ---> approximately step independent distribution (L.Urban)
// 21-09-04 change in the tail of the angular distribution (L.Urban)
//
// 03-11-04 precision problem for very high energy ions and small stepsize
// solved in SampleCosineTheta (L.Urban).
// 15-04-05 optimize internal interface - add SampleSecondaries method (V.Ivanchenko)
// 03-10-05 Model is freezed with the name McsModel71 (V.Ivanchenko)
// 17-02-06 Save table of transport cross sections not mfp (V.Ivanchenko)
//
// Class Description:
//
// Implementation of the model of multiple scattering based on
// H.W.Lewis Phys Rev 78 (1950) 526 and others
// -------------------------------------------------------------------
//
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
#include "G4MscModel71.hh"
#include "Randomize.hh"
#include "G4Electron.hh"
#include "G4LossTableManager.hh"
#include "G4PhysicsTable.hh"
#include "G4ParticleChangeForMSC.hh"
#include "G4TransportationManager.hh"
#include "G4Navigator.hh"
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
using namespace std;
G4MscModel71::G4MscModel71(G4double& m_dtrl, G4double& m_NuclCorrPar,
G4double& m_FactPar, G4double& m_factail,
G4bool& m_samplez, const G4String& nam)
: G4VEmModel(nam),
taubig(8.0),
tausmall(1.e-20),
taulim(1.e-6),
dtrl(m_dtrl),
NuclCorrPar (m_NuclCorrPar),
FactPar(m_FactPar),
factail(m_factail),
samplez(m_samplez),
isInitialized(false)
{
stepmin = 1.e-6*mm;
currentRange = 0. ;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4MscModel71::~G4MscModel71()
{}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
void G4MscModel71::Initialise(const G4ParticleDefinition* p,
const G4DataVector&)
{
if(isInitialized) return;
// set values of some data members
sigmafactor = twopi*classic_electr_radius*classic_electr_radius;
particle = p;
mass = particle->GetPDGMass();
charge = particle->GetPDGCharge()/eplus;
b = 1. ;
xsi = 3.00 ;
if(pParticleChange)
fParticleChange = reinterpret_cast<G4ParticleChangeForMSC*>(pParticleChange);
else
fParticleChange = new G4ParticleChangeForMSC();
navigator = G4TransportationManager::GetTransportationManager()
->GetNavigatorForTracking();
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4double G4MscModel71::ComputeCrossSectionPerAtom(
const G4ParticleDefinition* part,
G4double KineticEnergy,
G4double AtomicNumber,
G4double AtomicWeight,
G4double,
G4double)
{
const G4double epsfactor = 2.*electron_mass_c2*electron_mass_c2*
Bohr_radius*Bohr_radius/(hbarc*hbarc);
const G4double epsmin = 1.e-4 , epsmax = 1.e10;
const G4double Zdat[15] = { 4., 6.,13.,20.,26.,29.,32.,38.,47.,
50.,56.,64.,74.,79.,82. };
const G4double Tdat[23] = {0.0001*MeV,0.0002*MeV,0.0004*MeV,0.0007*MeV,
0.001*MeV,0.002*MeV,0.004*MeV,0.007*MeV,
0.01*MeV,0.02*MeV,0.04*MeV,0.07*MeV,
0.1*MeV,0.2*MeV,0.4*MeV,0.7*MeV,
1.*MeV,2.*MeV,4.*MeV,7.*MeV,10.*MeV,20.*MeV,
10000.0*MeV};
// corr. factors for e-/e+ lambda
G4double celectron[15][23] =
{{1.125,1.072,1.051,1.047,1.047,1.050,1.052,1.054,
1.054,1.057,1.062,1.069,1.075,1.090,1.105,1.111,
1.112,1.108,1.100,1.093,1.089,1.087,0.7235 },
{1.408,1.246,1.143,1.096,1.077,1.059,1.053,1.051,
1.052,1.053,1.058,1.065,1.072,1.087,1.101,1.108,
1.109,1.105,1.097,1.090,1.086,1.082,0.7925 },
{2.833,2.268,1.861,1.612,1.486,1.309,1.204,1.156,
1.136,1.114,1.106,1.106,1.109,1.119,1.129,1.132,
1.131,1.124,1.113,1.104,1.099,1.098,0.9147 },
{3.879,3.016,2.380,2.007,1.818,1.535,1.340,1.236,
1.190,1.133,1.107,1.099,1.098,1.103,1.110,1.113,
1.112,1.105,1.096,1.089,1.085,1.098,0.9700 },
{6.937,4.330,2.886,2.256,1.987,1.628,1.395,1.265,
1.203,1.122,1.080,1.065,1.061,1.063,1.070,1.073,
1.073,1.070,1.064,1.059,1.056,1.056,1.0022 },
{9.616,5.708,3.424,2.551,2.204,1.762,1.485,1.330,
1.256,1.155,1.099,1.077,1.070,1.068,1.072,1.074,
1.074,1.070,1.063,1.059,1.056,1.052,1.0158 },
{11.72,6.364,3.811,2.806,2.401,1.884,1.564,1.386,
1.300,1.180,1.112,1.082,1.073,1.066,1.068,1.069,
1.068,1.064,1.059,1.054,1.051,1.050,1.0284 },
{18.08,8.601,4.569,3.183,2.662,2.025,1.646,1.439,
1.339,1.195,1.108,1.068,1.053,1.040,1.039,1.039,
1.039,1.037,1.034,1.031,1.030,1.036,1.0515 },
{18.22,10.48,5.333,3.713,3.115,2.367,1.898,1.631,
1.498,1.301,1.171,1.105,1.077,1.048,1.036,1.033,
1.031,1.028,1.024,1.022,1.021,1.024,1.0834 },
{14.14,10.65,5.710,3.929,3.266,2.453,1.951,1.669,
1.528,1.319,1.178,1.106,1.075,1.040,1.027,1.022,
1.020,1.017,1.015,1.013,1.013,1.020,1.0937 },
{14.11,11.73,6.312,4.240,3.478,2.566,2.022,1.720,
1.569,1.342,1.186,1.102,1.065,1.022,1.003,0.997,
0.995,0.993,0.993,0.993,0.993,1.011,1.1140 },
{22.76,20.01,8.835,5.287,4.144,2.901,2.219,1.855,
1.677,1.410,1.224,1.121,1.073,1.014,0.986,0.976,
0.974,0.972,0.973,0.974,0.975,0.987,1.1410 },
{50.77,40.85,14.13,7.184,5.284,3.435,2.520,2.059,
1.837,1.512,1.283,1.153,1.091,1.010,0.969,0.954,
0.950,0.947,0.949,0.952,0.954,0.963,1.1750 },
{65.87,59.06,15.87,7.570,5.567,3.650,2.682,2.182,
1.939,1.579,1.325,1.178,1.108,1.014,0.965,0.947,
0.941,0.938,0.940,0.944,0.946,0.954,1.1922 },
{55.60,47.34,15.92,7.810,5.755,3.767,2.760,2.239,
1.985,1.609,1.343,1.188,1.113,1.013,0.960,0.939,
0.933,0.930,0.933,0.936,0.939,0.949,1.2026 }};
G4double cpositron[15][23] = {
{2.589,2.044,1.658,1.446,1.347,1.217,1.144,1.110,
1.097,1.083,1.080,1.086,1.092,1.108,1.123,1.131,
1.131,1.126,1.117,1.108,1.103,1.100,0.7235 },
{3.904,2.794,2.079,1.710,1.543,1.325,1.202,1.145,
1.122,1.096,1.089,1.092,1.098,1.114,1.130,1.137,
1.138,1.132,1.122,1.113,1.108,1.102,0.7925 },
{7.970,6.080,4.442,3.398,2.872,2.127,1.672,1.451,
1.357,1.246,1.194,1.179,1.178,1.188,1.201,1.205,
1.203,1.190,1.173,1.159,1.151,1.145,0.9147 },
{9.714,7.607,5.747,4.493,3.815,2.777,2.079,1.715,
1.553,1.353,1.253,1.219,1.211,1.214,1.225,1.228,
1.225,1.210,1.191,1.175,1.166,1.174,0.9700 },
{17.97,12.95,8.628,6.065,4.849,3.222,2.275,1.820,
1.624,1.382,1.259,1.214,1.202,1.202,1.214,1.219,
1.217,1.203,1.184,1.169,1.160,1.151,1.0022 },
{24.83,17.06,10.84,7.355,5.767,3.707,2.546,1.996,
1.759,1.465,1.311,1.252,1.234,1.228,1.238,1.241,
1.237,1.222,1.201,1.184,1.174,1.159,1.0158 },
{23.26,17.15,11.52,8.049,6.375,4.114,2.792,2.155,
1.880,1.535,1.353,1.281,1.258,1.247,1.254,1.256,
1.252,1.234,1.212,1.194,1.183,1.170,1.0284 },
{22.33,18.01,12.86,9.212,7.336,4.702,3.117,2.348,
2.015,1.602,1.385,1.297,1.268,1.251,1.256,1.258,
1.254,1.237,1.214,1.195,1.185,1.179,1.0515 },
{33.91,24.13,15.71,10.80,8.507,5.467,3.692,2.808,
2.407,1.873,1.564,1.425,1.374,1.330,1.324,1.320,
1.312,1.288,1.258,1.235,1.221,1.205,1.0834 },
{32.14,24.11,16.30,11.40,9.015,5.782,3.868,2.917,
2.490,1.925,1.596,1.447,1.391,1.342,1.332,1.327,
1.320,1.294,1.264,1.240,1.226,1.214,1.0937 },
{29.51,24.07,17.19,12.28,9.766,6.238,4.112,3.066,
2.602,1.995,1.641,1.477,1.414,1.356,1.342,1.336,
1.328,1.302,1.270,1.245,1.231,1.233,1.1140 },
{38.19,30.85,21.76,15.35,12.07,7.521,4.812,3.498,
2.926,2.188,1.763,1.563,1.484,1.405,1.382,1.371,
1.361,1.330,1.294,1.267,1.251,1.239,1.1410 },
{49.71,39.80,27.96,19.63,15.36,9.407,5.863,4.155,
3.417,2.478,1.944,1.692,1.589,1.480,1.441,1.423,
1.409,1.372,1.330,1.298,1.280,1.258,1.1750 },
{59.25,45.08,30.36,20.83,16.15,9.834,6.166,4.407,
3.641,2.648,2.064,1.779,1.661,1.531,1.482,1.459,
1.442,1.400,1.354,1.319,1.299,1.272,1.1922 },
{56.38,44.29,30.50,21.18,16.51,10.11,6.354,4.542,
3.752,2.724,2.116,1.817,1.692,1.554,1.499,1.474,
1.456,1.412,1.364,1.328,1.307,1.282,1.2026 }};
G4double sigma;
if (part != particle ) {
particle = part;
mass = particle->GetPDGMass();
charge = particle->GetPDGCharge()/eplus;
}
G4double Z23 = 2.*log(AtomicNumber)/3.; Z23 = exp(Z23);
// correction if particle .ne. e-/e+
// compute equivalent kinetic energy
// lambda depends on p*beta ....
G4double eKineticEnergy = KineticEnergy;
if((particle->GetParticleName() != "e-") &&
(particle->GetParticleName() != "e+") )
{
G4double TAU = KineticEnergy/mass ;
G4double c = mass*TAU*(TAU+2.)/(electron_mass_c2*(TAU+1.)) ;
G4double w = c-2. ;
G4double tau = 0.5*(w+sqrt(w*w+4.*c)) ;
eKineticEnergy = electron_mass_c2*tau ;
}
G4double ChargeSquare = charge*charge;
G4double eTotalEnergy = eKineticEnergy + electron_mass_c2 ;
G4double beta2 = eKineticEnergy*(eTotalEnergy+electron_mass_c2)
/(eTotalEnergy*eTotalEnergy);
G4double bg2 = eKineticEnergy*(eTotalEnergy+electron_mass_c2)
/(electron_mass_c2*electron_mass_c2);
G4double eps = epsfactor*bg2/Z23;
if (eps<epsmin) sigma = 2.*eps*eps;
else if(eps<epsmax) sigma = log(1.+2.*eps)-2.*eps/(1.+2.*eps);
else sigma = log(2.*eps)-1.+1./eps;
sigma *= ChargeSquare*AtomicNumber*AtomicNumber/(beta2*bg2);
// nuclear size effect correction for high energy
// ( a simple approximation at present)
G4double corrnuclsize,a,w1,w2,w;
G4double x0 = 1. - NuclCorrPar*mass/(KineticEnergy*
exp(log(AtomicWeight/(g/mole))/3.));
if ( x0 < -1. || eKineticEnergy <= 10.*MeV)
{
x0 = -1.;
corrnuclsize = 1.;
}
else
{
a = 1.+1./eps;
if (eps > epsmax) w1=log(2.*eps)+1./eps-3./(8.*eps*eps);
else w1=log((a+1.)/(a-1.))-2./(a+1.);
w = 1./((1.-x0)*eps);
if (w < epsmin) w2=-log(w)-1.+2.*w-1.5*w*w;
else w2 = log((a-x0)/(a-1.))-(1.-x0)/(a-x0);
corrnuclsize = w1/w2;
corrnuclsize = exp(-FactPar*mass/KineticEnergy)*
(corrnuclsize-1.)+1.;
}
// interpolate in AtomicNumber and beta2
// get bin number in Z
G4int iZ = 14;
while ((iZ>=0)&&(Zdat[iZ]>=AtomicNumber)) iZ -= 1;
if (iZ==14) iZ = 13;
if (iZ==-1) iZ = 0 ;
G4double Z1 = Zdat[iZ];
G4double Z2 = Zdat[iZ+1];
G4double ratZ = (AtomicNumber-Z1)/(Z2-Z1);
// get bin number in T (beta2)
G4int iT = 22;
while ((iT>=0)&&(Tdat[iT]>=eKineticEnergy)) iT -= 1;
if(iT==22) iT = 21;
if(iT==-1) iT = 0 ;
// calculate betasquare values
G4double T = Tdat[iT], E = T + electron_mass_c2;
G4double b2small = T*(E+electron_mass_c2)/(E*E);
T = Tdat[iT+1]; E = T + electron_mass_c2;
G4double b2big = T*(E+electron_mass_c2)/(E*E);
G4double ratb2 = (beta2-b2small)/(b2big-b2small);
G4double c1,c2,cc1,cc2,corr;
if (charge < 0.)
{
c1 = celectron[iZ][iT];
c2 = celectron[iZ+1][iT];
cc1 = c1+ratZ*(c2-c1);
c1 = celectron[iZ][iT+1];
c2 = celectron[iZ+1][iT+1];
cc2 = c1+ratZ*(c2-c1);
corr = cc1+ratb2*(cc2-cc1);
sigma /= corr;
}
if (charge > 0.)
{
c1 = cpositron[iZ][iT];
c2 = cpositron[iZ+1][iT];
cc1 = c1+ratZ*(c2-c1);
c1 = cpositron[iZ][iT+1];
c2 = cpositron[iZ+1][iT+1];
cc2 = c1+ratZ*(c2-c1);
corr = cc1+ratb2*(cc2-cc1);
sigma /= corr;
}
sigma *= sigmafactor;
// nucl. size correction for particles other than e+/e- only at present !!!!
if((particle->GetParticleName() != "e-") &&
(particle->GetParticleName() != "e+") )
sigma /= corrnuclsize;
// G4cout << "e= " << KineticEnergy << " sigma= " << sigma << G4endl;
return sigma;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4double G4MscModel71::GeomPathLength(
G4PhysicsTable* theLambdaTable,
const G4MaterialCutsCouple* couple,
const G4ParticleDefinition* theParticle,
G4double& T0,
G4double lambda,
G4double range,
G4double truePathLength)
{
// do the true -> geom transformation
const G4double ztmax = 101./103. ;
if (theParticle != particle ) {
particle = theParticle;
mass = particle->GetPDGMass();
charge = particle->GetPDGCharge()/eplus;
}
currentKinEnergy = T0;
currentRange = range ;
currentRadLength = couple->GetMaterial()->GetRadlen();
lambda0 = lambda;
par1 = -1. ;
par2 = par3 = 0. ;
tPathLength = truePathLength;
// this correction needed to run MSC with eIoni and eBrem inactivated
// and makes no harm for a normal run
if(tPathLength > range)
tPathLength = range ;
G4double tau = tPathLength/lambda0 ;
if (tau <= tausmall) return tPathLength;
G4double zmean = tPathLength;
if (tPathLength < range*dtrl) {
zmean = lambda0*(1.-exp(-tau));
if(tau < taulim) zmean = tPathLength*(1.-0.5*tPathLength/lambda0) ;
} else if(T0 < mass) {
par1 = 1./range ;
par2 = 1./(par1*lambda0) ;
par3 = 1.+par2 ;
zmean = (1.-exp(par3*log(1.-tPathLength/range)))/(par1*par3) ;
} else {
G4LossTableManager* theManager = G4LossTableManager::Instance();
G4double T1 = theManager->GetEnergy(particle,range-tPathLength,couple);
G4double lambda1 ;
if (theLambdaTable) {
G4bool bb;
lambda1 = ((*theLambdaTable)[couple->GetIndex()])->GetValue(T1,bb);
} else {
lambda1 = CrossSection(couple,particle,T1,0.0,1.0);
}
lambda1 = 1.0/lambda1;
par1 = (lambda0-lambda1)/(lambda0*tPathLength) ;
par2 = 1./(par1*lambda0) ;
par3 = 1.+par2 ;
zmean = (1.-exp(par3*log(lambda1/lambda0)))/(par1*par3) ;
}
// sample z
G4double zPathLength = zmean ;
G4double zt = zmean/tPathLength ;
if (tPathLength >= stepmin && samplez && zt > 0.5 && zt < ztmax)
{
G4double cz = 0.5*(3.*zt-1.)/(1.-zt) ;
G4double cz1 = 1.+cz ;
G4double u0 = cz/cz1 ;
G4double u,grej ;
do {
u = exp(log(G4UniformRand())/cz1) ;
grej = exp(cz*log(u/u0))*(1.-u)/(1.-u0) ;
} while (grej < G4UniformRand()) ;
zPathLength = tPathLength*u ;
}
return zPathLength ;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4double G4MscModel71::TrueStepLength(G4double geomStepLength)
{
G4double trueLength = geomStepLength;
trueLength = geomStepLength;
if(geomStepLength > lambda0*tausmall)
{
if(par1 < 0.)
trueLength = -lambda0*log(1.-geomStepLength/lambda0) ;
else
{
if(par1*par3*geomStepLength < 1.)
trueLength = (1.-exp(log(1.-par1*par3*geomStepLength)/par3))/par1 ;
else
trueLength = currentRange ;
}
}
if(trueLength > tPathLength) trueLength = tPathLength;
if(trueLength > currentRange) trueLength = currentRange ;
if(trueLength < geomStepLength) trueLength = geomStepLength;
return trueLength;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
std::vector<G4DynamicParticle*>* G4MscModel71::SampleSecondaries(
const G4MaterialCutsCouple*,
const G4DynamicParticle* dynParticle,
G4double truestep,
G4double safety)
{
G4double kineticEnergy = dynParticle->GetKineticEnergy();
if(kineticEnergy <= 0.0) return 0;
G4double cth = SampleCosineTheta(truestep,kineticEnergy);
G4double sth = sqrt((1.0 - cth)*(1.0 + cth));
G4double phi = twopi*G4UniformRand();
G4double dirx = sth*cos(phi);
G4double diry = sth*sin(phi);
G4ThreeVector oldDirection = dynParticle->GetMomentumDirection();
G4ThreeVector newDirection(dirx,diry,cth);
newDirection.rotateUz(oldDirection);
fParticleChange->ProposeMomentumDirection(newDirection);
/*
const G4ParticleDefinition* pd = dynParticle->GetDefinition();
G4cout << "G4MscModel71: Sample secondary; E(MeV)= " << kineticEnergy/MeV
<< " MeV; step(mm)= " << truestep/mm
<< ", safety(mm)= " << safety/mm << " " << pd->GetParticleName()
<< G4endl;
*/
if (latDisplasment && safety > 0.0) {
G4double r = SampleDisplacement();
if (r > safety) r = safety;
// sample direction of lateral displacement
G4double phi = twopi*G4UniformRand();
G4double dirx = std::cos(phi);
G4double diry = std::sin(phi);
G4ThreeVector newPosition(dirx,diry,0.0);
newPosition.rotateUz(oldDirection);
// compute new endpoint of the Step
newPosition *= r;
newPosition += *(fParticleChange->GetProposedPosition());
navigator->LocateGlobalPointWithinVolume(newPosition);
fParticleChange->ProposePosition(newPosition);
}
return 0;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4double G4MscModel71::SampleCosineTheta(G4double trueStepLength, G4double KineticEnergy)
{
G4double cth = 1. ;
G4double tau = trueStepLength/lambda0 ;
if(trueStepLength >= currentRange*dtrl)
if(par1*trueStepLength < 1.)
tau = -par2*log(1.-par1*trueStepLength) ;
else
tau = taubig ;
currentTau = tau ;
if(trueStepLength < stepmin)
cth = exp(-tau) ;
else
{
if (tau >= taubig) cth = -1.+2.*G4UniformRand();
else if (tau >= tausmall)
{
G4double a ;
// for all particles take the width of the central part
// from a parametrization similar to the Highland formula
// ( Highland formula: Particle Physics Booklet, July 2002, eq. 26.10)
// here : theta0 = 13.6*MeV*Q*(t/X0)**0.555/(beta*cp)
const G4double c_highland = 13.6*MeV, corr_highland=0.555 ;
G4double Q = std::abs(charge) ;
G4double xx0 = trueStepLength/currentRadLength;
G4double betacp = sqrt(currentKinEnergy*(currentKinEnergy+2.*mass)*
KineticEnergy*(KineticEnergy+2.*mass)/
((currentKinEnergy+mass)*(KineticEnergy+mass))) ;
G4double theta0 = c_highland*Q*exp(corr_highland*log(xx0))/betacp ;
if(theta0 > taulim) a = 0.5/(1.-cos(theta0)) ;
else a = 1.0/(theta0*theta0) ;
G4double xmeanth = exp(-tau);
G4double xmeanth1 = 1.-xmeanth ;
if(currentTau < taulim) xmeanth1 = tau ;
const G4double x1fac1 = exp(-xsi) ;
const G4double x1fac2 = (1.-(1.+xsi)*x1fac1)/(1.-x1fac1) ;
const G4double x1fac3 = 1.3 ;
G4double ea,eaa,xmean1 ;
G4double c = 2.,b1 = 2., bx = 2.,
eb1 = b1, ebx = b1, xmean2 = 0. ;
G4double prob = 1., qprob ;
G4double x0 = 1.-xsi/a;
G4double oneminusx0=xsi/a ;
G4double oneplusx0=2.+xsi/a ;
G4double f1x0=1., f2x0=1. ;
const G4double tau0 = 0.10 ;
if(tau > tau0)
{
// 1 model function
a = 1./xmeanth1 ;
ea = exp(-2.*a) ;
eaa= 1.-ea ;
xmean1 = 1.-1./a+2.*ea/eaa ;
prob = 1. ;
qprob = 1. ;
}
else if (x0 <= -1.)
{
// 2 model fuctions only
// in order to have xmean1 > xmeanth -> qprob < 1
x0 = -1.;
if( a < 1./xmeanth1)
a = 1./xmeanth1 ;
oneminusx0 = 1.-x0 ;
oneplusx0 = 1.+x0 ;
ea = exp(-a*oneminusx0);
eaa = 1.-ea ;
xmean1 = 1.-1./a+oneminusx0*ea/eaa ;
qprob = xmeanth/xmean1 ;
}
else
{
// 3 model fuctions
// in order to have xmean1 > xmeanth
if((1.-x1fac2/a) < xmeanth)
{
a = x1fac3*x1fac2/xmeanth1 ;
x0 = 1.-xsi/a ;
oneminusx0=xsi/a ;
oneplusx0=2.-xsi/a ;
}
ea = x1fac1 ;
eaa = 1.-ea ;
xmean1 = 1.-x1fac2/a ;
const G4double fctail = factail*1.0 ;
c = 2.+fctail*tau ;
G4double c1 = c-1. ;
G4double c2 = c-2. ;
if(c2 == 0.) c2 = fctail*tausmall ;
b = 1.+(c-xsi)/a ;
b1 = b+1. ;
bx = c/a ;
eb1=exp((c1)*log(b1)) ;
ebx=exp((c1)*log(bx)) ;
xmean2 = (x0*eb1+ebx-(eb1*bx-b1*ebx)/c2)/(eb1-ebx) ;
f1x0 = a*ea/eaa ;
f2x0 = c1*eb1*ebx/(eb1-ebx)/
exp(c*log(bx)) ;
// from continuity at x=x0
prob = f2x0/(f1x0+f2x0) ;
// from xmean = xmeanth
qprob = (f1x0+f2x0)*xmeanth/(f2x0*xmean1+f1x0*xmean2) ;
}
// sampling of costheta
if (G4UniformRand() < qprob)
{
if (G4UniformRand() < prob)
cth = 1.+log(ea+G4UniformRand()*eaa)/a ;
else
cth = b-b1*bx/exp(log(ebx-G4UniformRand()*(ebx-eb1))/(c-1.)) ;
}
else
{
cth = -1.+2.*G4UniformRand();
}
}
}
return cth ;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4double G4MscModel71::SampleDisplacement()
{
const G4double kappa = 2.5;
const G4double kappapl1 = kappa+1.;
const G4double kappami1 = kappa-1.;
G4double rmean = 0.0;
if (currentTau >= tausmall) {
if (currentTau < taulim) {
rmean = kappa*currentTau*currentTau*currentTau*(1.-kappapl1*currentTau*0.25)/6. ;
} else {
G4double etau = 0.0;
if (currentTau<taubig) etau = exp(-currentTau);
rmean = -kappa*currentTau;
rmean = -exp(rmean)/(kappa*kappami1);
rmean += currentTau-kappapl1/kappa+kappa*etau/kappami1;
}
if (rmean>0.) rmean = 2.*lambda0*sqrt(rmean/3.0);
else rmean = 0.;
}
return rmean;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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