| Geant4 Cross Reference |
1 //
2 // ********************************************************************
3 // * License and Disclaimer *
4 // * *
5 // * The Geant4 software is copyright of the Copyright Holders of *
6 // * the Geant4 Collaboration. It is provided under the terms and *
7 // * conditions of the Geant4 Software License, included in the file *
8 // * LICENSE and available at http://cern.ch/geant4/license . These *
9 // * include a list of copyright holders. *
10 // * *
11 // * Neither the authors of this software system, nor their employing *
12 // * institutes,nor the agencies providing financial support for this *
13 // * work make any representation or warranty, express or implied, *
14 // * regarding this software system or assume any liability for its *
15 // * use. Please see the license in the file LICENSE and URL above *
16 // * for the full disclaimer and the limitation of liability. *
17 // * *
18 // * This code implementation is the result of the scientific and *
19 // * technical work of the GEANT4 collaboration. *
20 // * By using, copying, modifying or distributing the software (or *
21 // * any work based on the software) you agree to acknowledge its *
22 // * use in resulting scientific publications, and indicate your *
23 // * acceptance of all terms of the Geant4 Software license. *
24 // ********************************************************************
25 //
26 // -------------------------------------------------------------------
27 //
28 // Geant4 Class file
29 //
30 // File name: G4PolarizedIonisationMollerXS
31 //
32 // Author: Andreas Schaelicke
33 //
34 // Class Description:
35 // * calculates the differential cross section
36 // incoming electron K1(along positive z direction) scatters at an electron
37 // K2 at rest
38 // * phi denotes the angle between the scattering plane (defined by the
39 // outgoing electron) and X-axis
40 // * all stokes vectors refer to spins in the Global System (X,Y,Z)
41 // * cross section as calculated by P.Starovoitov
42
43 #include "G4PolarizedIonisationMollerXS.hh"
44
45 #include "G4PhysicalConstants.hh"
46
47 G4PolarizedIonisationMollerXS::G4PolarizedIonisationMollerXS()
48 : fPhi0(0.)
49 {
50 SetXmax(.5);
51 fPhi2 = G4ThreeVector(0., 0., 0.);
52 fPhi3 = G4ThreeVector(0., 0., 0.);
53 }
54
55 G4PolarizedIonisationMollerXS::~G4PolarizedIonisationMollerXS() {}
56
57 void G4PolarizedIonisationMollerXS::Initialize(G4double e, G4double gamma,
58 G4double /*phi*/,
59 const G4StokesVector& pol0,
60 const G4StokesVector& pol1,
61 G4int flag)
62 {
63 constexpr G4double re2 = classic_electr_radius * classic_electr_radius;
64 G4double gamma2 = gamma * gamma;
65 G4double gmo = (gamma - 1.);
66 G4double gmo2 = (gamma - 1.) * (gamma - 1.);
67 G4double gpo = (gamma + 1.);
68 G4double pref = gamma2 * re2 / (gmo2 * (gamma + 1.0));
69 constexpr G4double sqrttwo = 1.41421356237309504880; // sqrt(2.)
70 G4double f = (-1. + e);
71 G4double e2 = e * e;
72 G4double f2 = f * f;
73
74 G4bool polarized = (!pol0.IsZero()) || (!pol1.IsZero());
75
76 if(flag == 0)
77 polarized = false;
78 // Unpolarised part of XS
79 fPhi0 = gmo2 / gamma2;
80 fPhi0 += ((1. - 2. * gamma) / gamma2) * (1. / e + 1. / (1. - e));
81 fPhi0 += 1. / (e * e) + 1. / ((1. - e) * (1. - e));
82 fPhi0 *= 0.25;
83 // Initial state polarisarion dependence
84 if(polarized)
85 {
86 G4bool usephi = true;
87 if(flag <= 1)
88 usephi = false;
89 G4double xx = (gamma - f * e * gmo * (3. + gamma)) / (4. * f * e * gamma2);
90 G4double yy = (-1. + f * e * gmo2 + 2. * gamma) / (4. * f * e * gamma2);
91 G4double zz = (-(e * gmo * (3. + gamma)) + e2 * gmo * (3. + gamma) +
92 gamma * (-1. + 2. * gamma)) /
93 (4. * f * e * gamma2);
94
95 fPhi0 += xx * pol0.x() * pol1.x() + yy * pol0.y() * pol1.y() +
96 zz * pol0.z() * pol1.z();
97
98 if(usephi)
99 {
100 G4double xy = 0.;
101 G4double xz = -((-1. + 2. * e) * gmo) /
102 (2. * sqrttwo * gamma2 * std::sqrt(-((f * e) / gpo)));
103 G4double yx = 0.;
104 G4double yz = 0.;
105 G4double zx = -((-1. + 2. * e) * gmo) /
106 (2. * sqrttwo * gamma2 * std::sqrt(-((f * e) / gpo)));
107 G4double zy = 0.;
108 fPhi0 += yx * pol0.y() * pol1.x() + xy * pol0.x() * pol1.y();
109 fPhi0 += zx * pol0.z() * pol1.x() + xz * pol0.x() * pol1.z();
110 fPhi0 += zy * pol0.z() * pol1.y() + yz * pol0.y() * pol1.z();
111 }
112 }
113 // Final state polarisarion dependence
114 fPhi2 = G4ThreeVector();
115 fPhi3 = G4ThreeVector();
116
117 if(flag >= 1)
118 {
119 // Final Electron P1
120 // initial electron K1
121 if(!pol0.IsZero())
122 {
123 G4double xxP1K1 =
124 (std::sqrt(gpo / (1. + e2 * gmo + gamma - 2. * e * gamma)) *
125 (gamma - e * gpo)) /
126 (4. * e2 * gamma);
127 G4double xyP1K1 = 0.;
128 G4double xzP1K1 = (-1. + 2. * e * gamma) /
129 (2. * sqrttwo * f * gamma *
130 std::sqrt(e * e2 * (1. + e + gamma - e * gamma)));
131 G4double yxP1K1 = 0.;
132 G4double yyP1K1 =
133 (-gamma2 + e * (-1. + gamma * (2. + gamma))) / (4. * f * e2 * gamma2);
134 G4double yzP1K1 = 0.;
135 G4double zxP1K1 = (1. + 2. * e2 * gmo - 2. * e * gamma) /
136 (2. * sqrttwo * f * e * gamma *
137 std::sqrt(e * (1. + e + gamma - e * gamma)));
138 G4double zyP1K1 = 0.;
139 G4double zzP1K1 =
140 (-gamma + e * (1. - 2. * e * gmo + gamma)) /
141 (4. * f * e2 * gamma * std::sqrt(1. - (2. * e) / (f * gpo)));
142 fPhi2[0] += xxP1K1 * pol0.x() + xyP1K1 * pol0.y() + xzP1K1 * pol0.z();
143 fPhi2[1] += yxP1K1 * pol0.x() + yyP1K1 * pol0.y() + yzP1K1 * pol0.z();
144 fPhi2[2] += zxP1K1 * pol0.x() + zyP1K1 * pol0.y() + zzP1K1 * pol0.z();
145 }
146 // initial electron K2
147 if(!pol1.IsZero())
148 {
149 G4double xxP1K2 =
150 ((1. + e * (-3. + gamma)) *
151 std::sqrt(gpo / (1. + e2 * gmo + gamma - 2. * e * gamma))) /
152 (4. * f * e * gamma);
153 G4double xyP1K2 = 0.;
154 G4double xzP1K2 =
155 (-2. + 2. * e + gamma) / (2. * sqrttwo * f2 * gamma *
156 std::sqrt(e * (1. + e + gamma - e * gamma)));
157 G4double yxP1K2 = 0.;
158 G4double yyP1K2 = (1. - 2. * gamma + e * (-1. + gamma * (2. + gamma))) /
159 (4. * f2 * e * gamma2);
160 G4double yzP1K2 = 0.;
161 G4double zxP1K2 = (2. * e * (1. + e * gmo - 2. * gamma) + gamma) /
162 (2. * sqrttwo * f2 * gamma *
163 std::sqrt(e * (1. + e + gamma - e * gamma)));
164 G4double zyP1K2 = 0.;
165 G4double zzP1K2 =
166 (1. - 2. * gamma + e * (-1. - 2. * e * gmo + 3. * gamma)) /
167 (4. * f2 * e * gamma * std::sqrt(1. - (2. * e) / (f * gpo)));
168 fPhi2[0] += xxP1K2 * pol1.x() + xyP1K2 * pol1.y() + xzP1K2 * pol1.z();
169 fPhi2[1] += yxP1K2 * pol1.x() + yyP1K2 * pol1.y() + yzP1K2 * pol1.z();
170 fPhi2[2] += zxP1K2 * pol1.x() + zyP1K2 * pol1.y() + zzP1K2 * pol1.z();
171 }
172
173 // Final Electron P2
174 // initial electron K1
175 if(!pol0.IsZero())
176 {
177 G4double xxP2K1 =
178 (-1. + e + e * gamma) /
179 (4. * f2 * gamma * std::sqrt((e * (2. + e * gmo)) / gpo));
180 G4double xyP2K1 = 0.;
181 G4double xzP2K1 =
182 -((1. + 2. * f * gamma) * std::sqrt(f / (-2. + e - e * gamma))) /
183 (2. * sqrttwo * f2 * e * gamma);
184 G4double yxP2K1 = 0.;
185 G4double yyP2K1 = (1. - 2. * gamma + e * (-1. + gamma * (2. + gamma))) /
186 (4. * f2 * e * gamma2);
187 G4double yzP2K1 = 0.;
188 G4double zxP2K1 =
189 (1. + 2. * e * (-2. + e + gamma - e * gamma)) /
190 (2. * sqrttwo * f * e * std::sqrt(-(f * (2. + e * gmo))) * gamma);
191 G4double zyP2K1 = 0.;
192 G4double zzP2K1 =
193 (std::sqrt((e * gpo) / (2. + e * gmo)) *
194 (-3. + e * (5. + 2. * e * gmo - 3. * gamma) + 2. * gamma)) /
195 (4. * f2 * e * gamma);
196
197 fPhi3[0] += xxP2K1 * pol0.x() + xyP2K1 * pol0.y() + xzP2K1 * pol0.z();
198 fPhi3[1] += yxP2K1 * pol0.x() + yyP2K1 * pol0.y() + yzP2K1 * pol0.z();
199 fPhi3[2] += zxP2K1 * pol0.x() + zyP2K1 * pol0.y() + zzP2K1 * pol0.z();
200 }
201 // initial electron K2
202 if(!pol1.IsZero())
203 {
204 G4double xxP2K2 =
205 (-2. - e * (-3. + gamma) + gamma) /
206 (4. * f * e * gamma * std::sqrt((e * (2. + e * gmo)) / gpo));
207 G4double xyP2K2 = 0.;
208 G4double xzP2K2 =
209 ((-2. * e + gamma) * std::sqrt(f / (-2. + e - e * gamma))) /
210 (2. * sqrttwo * f * e2 * gamma);
211 G4double yxP2K2 = 0.;
212 G4double yyP2K2 =
213 (-gamma2 + e * (-1. + gamma * (2. + gamma))) / (4. * f * e2 * gamma2);
214 G4double yzP2K2 = 0.;
215 G4double zxP2K2 =
216 (gamma + 2. * e * (-1. + e - e * gamma)) /
217 (2. * sqrttwo * e2 * std::sqrt(-(f * (2. + e * gmo))) * gamma);
218 G4double zyP2K2 = 0.;
219 G4double zzP2K2 = (std::sqrt((e * gpo) / (2. + e * gmo)) *
220 (-2. + e * (3. + 2. * e * gmo - gamma) + gamma)) /
221 (4. * f * e2 * gamma);
222 fPhi3[0] += xxP2K2 * pol1.x() + xyP2K2 * pol1.y() + xzP2K2 * pol1.z();
223 fPhi3[1] += yxP2K2 * pol1.x() + yyP2K2 * pol1.y() + yzP2K2 * pol1.z();
224 fPhi3[2] += zxP2K2 * pol1.x() + zyP2K2 * pol1.y() + zzP2K2 * pol1.z();
225 }
226 }
227 fPhi0 *= pref;
228 fPhi2 *= pref;
229 fPhi3 *= pref;
230 }
231
232 G4double G4PolarizedIonisationMollerXS::XSection(const G4StokesVector& pol2,
233 const G4StokesVector& pol3)
234 {
235 G4double xs = fPhi0;
236
237 G4bool polarized = (!pol2.IsZero()) || (!pol3.IsZero());
238 if(polarized)
239 {
240 xs += fPhi2 * pol2 + fPhi3 * pol3;
241 }
242 return xs;
243 }
244
245 G4double G4PolarizedIonisationMollerXS::TotalXSection(
246 G4double xmin, G4double xmax, G4double gamma, const G4StokesVector& pol0,
247 const G4StokesVector& pol1)
248 {
249 G4double xs = 0.;
250 G4double x = xmin;
251
252 if(xmax != 0.5)
253 {
254 G4ExceptionDescription ed;
255 ed << " warning xmax expected to be 1/2 but is " << xmax << "\n";
256 G4Exception("G4PolarizedIonisationMollerXS::TotalXSection", "pol020",
257 JustWarning, ed);
258 }
259
260 constexpr G4double re2 = classic_electr_radius * classic_electr_radius;
261 G4double gamma2 = gamma * gamma;
262 G4double gmo2 = (gamma - 1.) * (gamma - 1.);
263 G4double logMEM = std::log(1. / x - 1.);
264 G4double pref = twopi * gamma2 * re2 / (gmo2 * (gamma + 1.0));
265 // unpolarised XS
266 G4double sigma0 = (gmo2 / gamma2) * (0.5 - x);
267 sigma0 += ((1. - 2. * gamma) / gamma2) * logMEM;
268 sigma0 += 1. / x - 1. / (1. - x);
269 // longitudinal part
270 G4double sigma2 = ((gamma2 + 2. * gamma - 3.) / gamma2) * (0.5 - x);
271 sigma2 += (1. / gamma - 2.) * logMEM;
272 // transverse part
273 G4double sigma3 = (2. * (1. - gamma) / gamma2) * (0.5 - x);
274 sigma3 += (1. - 3. * gamma) / (2. * gamma2) * logMEM;
275 // total cross section
276 xs += pref * (sigma0 + sigma2 * pol0.z() * pol1.z() +
277 sigma3 * (pol0.x() * pol1.x() + pol0.y() * pol1.y()));
278
279 return xs;
280 }
281
282 G4StokesVector G4PolarizedIonisationMollerXS::GetPol2()
283 {
284 // Note, mean polarization can not contain correlation effects.
285 return G4StokesVector(1. / fPhi0 * fPhi2);
286 }
287 G4StokesVector G4PolarizedIonisationMollerXS::GetPol3()
288 {
289 // Note, mean polarization can not contain correlation effects.
290 return G4StokesVector(1. / fPhi0 * fPhi3);
291 }
292