source: trunk/source/processes/electromagnetic/polarisation/src/G4PolarizedComptonCrossSection.cc@ 819

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25//
26// $Id: G4PolarizedComptonCrossSection.cc,v 1.4 2007/11/01 17:32:34 schaelic Exp $
27// GEANT4 tag $Name: $
28//
29// GEANT4 Class file
30//
31//
32// File name: G4PolarizedComptonCrossSection
33//
34// Author: Andreas Schaelicke
35//
36// Creation date: 15.05.2005
37//
38// Modifications:
39//
40// Class Description:
41// determine the polarization of the final state
42// in a Compton scattering process employing the differential
43// cross section by F.W.Lipps & H.A.Tolhoek
44// ( Physica 20 (1954) 395 )
45// recalculated by P.Starovoitov
46//
47#include "G4PolarizedComptonCrossSection.hh"
48#include "Randomize.hh"
49
50//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
51G4PolarizedComptonCrossSection::G4PolarizedComptonCrossSection()
52 {
53 SetYmin(0.);
54
55 // G4cout<<"G4PolarizedComptonCrossSection() init\n";
56
57 re2 = classic_electr_radius * classic_electr_radius * sqr(4*pi/hbarc);
58 // G4double unit_conversion = hbarc_squared ;
59 // G4cout<<" (keV)^2* m^2 ="<<unit_conversion<<"\n";
60 phi0 = 0.; polXS = 0.; unpXS = 0.;
61 phi2 = G4ThreeVector(0., 0., 0.);
62 phi3 = G4ThreeVector(0., 0., 0.);
63 polxx = polyy = polzz = polxz = polzx = polyz = polzy = polxy = polyx = 0.;
64 diffXSFactor = 1.;
65 totalXSFactor = 1.;
66}
67
68//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
69G4PolarizedComptonCrossSection::~G4PolarizedComptonCrossSection()
70{}
71
72//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
73void G4PolarizedComptonCrossSection::Initialize(G4double eps, G4double X, G4double , // phi
74 const G4StokesVector & pol0,
75 const G4StokesVector & pol1,
76 G4int flag)
77{
78 G4double cosT = 1. - (1./eps - 1.)/X;
79 if(cosT > 1.+1.e-8) cosT = 1.;
80 if(cosT < -1.-1.e-8) cosT = -1.;
81 G4double cosT2 = cosT*cosT;
82 G4double cosT3 = cosT2*cosT;
83 G4double sinT2 = 1. - cosT2;
84 if(sinT2 > 1. + 1.e-8) sinT2 = 1.;
85 if(sinT2 < 0.) sinT2 = 0.;
86 G4double sinT = std::sqrt(sinT2);
87 G4double cos2T = 2.*cosT2 - 1.;
88 G4double sin2T = 2.*sinT*cosT;
89 G4double eps2 = sqr(eps);
90 DefineCoefficients(pol0,pol1);
91 diffXSFactor = re2/(4.*X);
92
93 // unpolarized Cross Section
94 unpXS = (eps2 + 1. - eps*sinT2)/(2.*eps);
95 // initial polarization dependence
96 polXS = -sinT2*pol0.x() + (1. - eps)*sinT*polzx + ((eps2 - 1.)/eps)*cosT*polzz;
97 polXS *= 0.5;
98
99 phi0 = unpXS + polXS;
100
101 if (flag == 2 ){
102 // polarization of outgoing photon
103 G4double PHI21 = -sinT2 + 0.5*(cos2T + 3.)*pol0.x() - ((1. - eps)/eps)*sinT*polzx;
104 PHI21 *= 0.5;
105 G4double PHI22 = cosT*pol0.y() + ((1. - eps)/(2.*eps))*sinT*polzy;
106 G4double PHI23 = ((eps2 + 1.)/eps)*cosT*pol0.z() - ((1. - eps)/eps)*(eps*cosT2 + 1.)*pol1.z();
107 PHI23 += 0.5*(1. - eps)*sin2T*pol1.x();
108 PHI23 += (eps - 1.)*(-sinT2*polxz + sinT*polyy - 0.5*sin2T*polxx);
109 PHI23 *= 0.5;
110 phi2 = G4ThreeVector(PHI21, PHI22, PHI23);
111
112 // polarization of outgoing electron
113 G4double PHI32 = -sinT2*polxy + ((1. - eps)/eps)*sinT*polyz + 0.5*(cos2T + 3.)*pol1.y();
114 PHI32 *= 0.5;
115
116 G4double PHI31 = 0., PHI31add = 0., PHI33 = 0., PHI33add = 0.;
117
118 if ((1. - eps) > 1.e-12){
119 G4double helpVar = std::sqrt(eps2 - 2.*cosT*eps + 1.);
120
121 PHI31 = (1. - eps)*(1. + cosT)*sinT*pol0.z();
122 PHI31 += (-eps*cosT3 + eps*cosT2 + (eps - 2.)*cosT + eps)*pol1.x();
123 PHI31 += -(eps*cosT2 - eps*cosT + cosT + 1.)*sinT*pol1.z();
124 PHI31 /= 2.*helpVar;
125
126 PHI31add = -eps*sqr(1. - cosT)*(1. + cosT)*polxx;
127 PHI31add += (1. - eps)*sinT2*polyy;
128 PHI31add += -(-eps2 + cosT*(cosT*eps - eps + 1.)*eps + eps - 1.)*sinT*polxz/eps;
129 PHI31add /= 2.*helpVar;
130
131 PHI33 = ((1. - eps)/eps)*(-eps*cosT2 + eps*(eps + 1.)*cosT - 1.)*pol0.z();
132 PHI33 += -(eps*cosT2 + (1. - eps)*eps*cosT + 1.)*sinT*pol1.x();
133 PHI33 += -(-eps2*cosT3 + eps*(eps2 - eps + 1.)*cosT2 - cosT + eps2)*pol1.z()/eps;
134 PHI33 /= -2.*helpVar;
135
136 PHI33add = (eps*(eps - cosT - 1.)*cosT + 1.)*sinT*polxx;
137 PHI33add += -(-eps2 + cosT*eps + eps - 1.)*sinT2*polxz;
138 PHI33add += (eps - 1.)*(cosT - eps)*sinT*polyy;
139 PHI33add /= -2.*helpVar;
140 }else{
141 PHI31 = -pol1.z() - (X - 1.)*std::sqrt(1. - eps)*pol1.x()/std::sqrt(2.*X);
142 PHI31add = -(-X*X*pol1.z() - 2.*X*(2.*pol0.z() - pol1.z()) - (4.*pol0.x() + 5.)*pol1.z())*(1. - eps)/(4.*X);
143
144 PHI33 = pol1.x() - (X - 1.)*std::sqrt(1. - eps)*pol1.z()/std::sqrt(2.*X);
145 PHI33add = -(X*X - 2.*X + 4.*pol0.x() + 5.)*(1. - eps)*pol1.x()/(4.*X);
146 }
147 phi3 = G4ThreeVector(PHI31 + PHI31add, PHI32, PHI33 + PHI33add);
148
149 }
150 unpXS *= diffXSFactor;
151 polXS *= diffXSFactor;
152 phi0 *= diffXSFactor;
153 phi2 *= diffXSFactor;
154 phi3 *= diffXSFactor;
155
156}
157
158G4double G4PolarizedComptonCrossSection::XSection(const G4StokesVector & pol2,const G4StokesVector & pol3)
159{
160 gammaPol2 = !(pol2==G4StokesVector::ZERO);
161 electronPol3 = !(pol3==G4StokesVector::ZERO);
162
163 G4double phi = 0.;
164 // polarization independent part
165 phi += phi0;
166
167
168 if (gammaPol2) {
169 // part depending on the polarization of the final photon
170 phi += phi2*pol2;
171 }
172
173 if (electronPol3) {
174 // part depending on the polarization of the final electron
175 phi += phi3*pol3;
176 }
177
178 // return cross section.
179 return phi;
180}
181
182//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
183
184
185G4double G4PolarizedComptonCrossSection::TotalXSection(G4double /*xmin*/, G4double /*xmax*/, G4double k0,
186 const G4StokesVector & pol0,
187 const G4StokesVector & pol1)
188{
189
190 // G4double k0 = gammaEnergy / electron_mass_c2 ;
191 G4double k1 = 1 + 2*k0 ;
192
193// // pi*re^2
194// G4double re=2.81794e-15; //m
195// G4double barn=1.e-28; //m^2
196 G4double Z=theZ;
197
198 G4double unit = Z*pi*classic_electr_radius
199 * classic_electr_radius ; // *1./barn;
200
201 G4double pre = unit/(sqr(k0)*sqr(1.+2.*k0));
202
203 G4double xs_0 = ((k0 - 2.)*k0 -2.)*sqr(k1)*std::log(k1) + 2.*k0*(k0*(k0 + 1.)*(k0 + 8.) + 2.);
204 G4double xs_pol = (k0 + 1.)*sqr(k1)*std::log(k1) - 2.*k0*(5.*sqr(k0) + 4.*k0 + 1.);
205
206 return pre*(xs_0/k0 + pol0.p3()*pol1.z()*xs_pol);
207}
208
209
210//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
211
212
213G4StokesVector G4PolarizedComptonCrossSection::GetPol2()
214{
215 // Note, mean polarization can not contain correlation
216 // effects.
217 return 1./phi0 * phi2;
218}
219
220//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
221
222G4StokesVector G4PolarizedComptonCrossSection::GetPol3()
223{
224 // Note, mean polarization can not contain correlation
225 // effects.
226 return 1./phi0 * phi3;
227}
228
229
230
231//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
232void G4PolarizedComptonCrossSection::DefineCoefficients(const G4StokesVector & pol0,
233 const G4StokesVector & pol1)
234{
235 polxx=pol0.x()*pol1.x();
236 polyy=pol0.y()*pol1.y();
237 polzz=pol0.z()*pol1.z();
238
239 polxz=pol0.x()*pol1.z();
240 polzx=pol0.z()*pol1.x();
241
242 polyz=pol0.y()*pol1.z();
243 polzy=pol0.z()*pol1.y();
244
245 polxy=pol0.x()*pol1.y();
246 polyx=pol0.y()*pol1.x();
247}
248
249
250//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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