Geant4 9.6.0
Toolkit for the simulation of the passage of particles through matter
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G4PolarizedBhabhaCrossSection.cc
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25//
26// $Id$
27// -------------------------------------------------------------------
28//
29// GEANT4 Class file
30//
31//
32// File name: G4PolarizedBhabhaCrossSection
33//
34// Author: Andreas Schaelicke
35//
36// Creation date: 12.01.2006
37//
38// Modifications:
39// 16-01-06 included cross section as calculated by P.Starovoitov
40// 24-08-06 bugfix in total cross section (A. Schaelicke)
41// 07-11-06 modify reference system for polarisation vectors
42// (A. Schaelicke & P.Starovoitov)
43//
44// Class Description:
45// * calculates the differential cross section
46// incomming positron Kpl(along positive z direction) scatters at
47// an electron Kmn at rest
48// * phi denotes the angle between the scattering plane (defined by the
49// outgoing electron) and X-axis
50// * all stokes vectors refer to spins in the Global System (X,Y,Z)
51//
52
53#include "G4PolarizedBhabhaCrossSection.hh"
54#include "G4PhysicalConstants.hh"
55
56G4PolarizedBhabhaCrossSection::G4PolarizedBhabhaCrossSection() : phi0(1.)
57{
58}
59G4PolarizedBhabhaCrossSection::~G4PolarizedBhabhaCrossSection()
60{
61}
62void G4PolarizedBhabhaCrossSection::Initialize(
63 G4double e,
64 G4double gamma,
65 G4double /*phi*/,
66 const G4StokesVector & pol0,
67 const G4StokesVector & pol1,
68 G4int flag)
69{
70 SetXmax(1.);
71
72 G4double re2 = classic_electr_radius * classic_electr_radius;
73 G4double gamma2 = gamma*gamma;
74 G4double gamma3 = gamma2*gamma;
75 G4double gmo = (gamma - 1.);
76 G4double gmo2 = (gamma - 1.)*(gamma - 1.);
77 G4double gmo3 = gmo2*(gamma - 1.);
78 G4double gpo = (gamma + 1.);
79 G4double gpo2 = (gamma + 1.)*(gamma + 1.);
80 G4double gpo3 = gpo2*(gamma + 1.);
81 G4double gpo12 = std::sqrt(gpo);
82 G4double gpo32 = gpo*gpo12;
83 G4double gpo52 = gpo2*gpo12;
84
85 G4double pref = re2/(gamma - 1.0);
86 G4double sqrttwo=std::sqrt(2.);
87 G4double d = std::sqrt(1./e - 1.);
88 G4double e2 = e*e;
89 G4double e3 = e2*e;
90
91 // *** new ***
92 G4double gmo12 = std::sqrt(gmo);
93 G4double gmo32 = gmo*gmo12;
94 G4double egmp32 = std::pow(e*(2 + e*gmo)*gpo,(3./2.));
95 G4double e32 = e*std::sqrt(e);
96
97 G4bool polarized=(!pol0.IsZero())||(!pol1.IsZero());
98
99 if (flag==0) polarized=false;
100 // Unpolarised part of XS
101 // *AS* UnpME . OK
102 phi0 = 0.;
103 phi0+= e2*gmo3/gpo3;
104 phi0+= -2.*e*gamma*gmo2/gpo3;
105 phi0+= (3.*gamma2 + 6.*gamma + 4.)*gmo/gpo3;
106 phi0+= -(2.*gamma2 + 4.*gamma + 1.)/(e*gpo2);
107 phi0+= gamma2/(e2*(gamma2 - 1.));
108 phi0*=0.25;
109 // Initial state polarisarion dependence
110 if (polarized) {
111 // G4cout<<"Polarized differential Bhabha cross section"<<G4endl;
112 // G4cout<<"Initial state polarisation contributions"<<G4endl;
113 // G4cout<<"Diagonal Matrix Elements"<<G4endl;
114 // *** new ***
115 G4double xx = -((e*gmo - gamma)*(-1 - gamma + e*(e*gmo - gamma)*(3 + gamma)))/(4*e*gpo3);
116 G4double yy = (e3*gmo3 - 2*e2*gmo2*gamma - gpo*(1 + 2*gamma) + e*(-2 + gamma2 + gamma3))/(4*e*gpo3);
117 G4double zz = ((e*gmo - gamma)*(e2*gmo*(3 + gamma) - e*gamma*(3 + gamma) + gpo*(1 + 2*gamma)))/(4*e*gpo3);
118 // ***
119
120 phi0 += xx*pol0.x()*pol1.x() + yy*pol0.y()*pol1.y() + zz*pol0.z()*pol1.z();
121
122 {
123 G4double xy = 0;
124 G4double xz = (d*(e*gmo - gamma)*(-1 + 2*e*gmo - gamma))/(2*sqrttwo*gpo52);
125 G4double yx = 0;
126 G4double yz = 0;
127 G4double zx = xz;
128 G4double zy = 0;
129 // G4cout<<"Non-diagonal Matrix Elements"<<G4endl;
130 phi0+=yx*pol0.y()*pol1.x() + xy*pol0.x()*pol1.y();
131 phi0+=zx*pol0.z()*pol1.x() + xz*pol0.x()*pol1.z();
132 phi0+=zy*pol0.z()*pol1.y() + yz*pol0.y()*pol1.z();
133 }
134 }
135 // Final state polarisarion dependence
136 phi2=G4ThreeVector();
137 phi3=G4ThreeVector();
138
139 if (flag>=1) {
140 //
141 // Final Positron Ppl
142 //
143 // initial positron Kpl
144 if (!pol0.IsZero()) {
145
146 G4double xxPplKpl = -((-1 + e)*(e*gmo - gamma)*(-(gamma*gpo) + e*(-2 + gamma + gamma2)))/
147 (4*e2*gpo*std::sqrt(gmo*gpo*(-1 + e + gamma - e*gamma)* (1 + e + gamma - e*gamma)));
148 G4double xyPplKpl = 0;
149 G4double xzPplKpl = ((e*gmo - gamma)*(-1 - gamma + e*gmo*(1 + 2*gamma)))/
150 (2*sqrttwo*e32*gmo*gpo2*std::sqrt(1 + e + gamma - e*gamma));
151 G4double yxPplKpl = 0;
152 G4double yyPplKpl = (gamma2*gpo + e2*gmo2*(3 + gamma) -
153 e*gmo*(1 + 2*gamma*(2 + gamma)))/(4*e2*gmo*gpo2);
154 G4double yzPplKpl = 0;
155 G4double zxPplKpl = ((e*gmo - gamma)*(1 + e*(-1 + 2*e*gmo - 2*gamma)*gmo + gamma))/
156 (2*sqrttwo*e*gmo*gpo2*std::sqrt(e*(1 + e + gamma - e*gamma)));
157 G4double zyPplKpl = 0;
158 G4double zzPplKpl = -((e*gmo - gamma)*std::sqrt((1 - e)/(e - e*gamma2 + gpo2))*
159 (2*e2*gmo2 + gamma + gamma2 - e*(-2 + gamma + gamma2)))/
160 (4*e2*(-1 + gamma2));
161
162 phi2[0] += xxPplKpl*pol0.x() + xyPplKpl*pol0.y() + xzPplKpl*pol0.z();
163 phi2[1] += yxPplKpl*pol0.x() + yyPplKpl*pol0.y() + yzPplKpl*pol0.z();
164 phi2[2] += zxPplKpl*pol0.x() + zyPplKpl*pol0.y() + zzPplKpl*pol0.z();
165 }
166 // initial electron Kmn
167 if (!pol1.IsZero()) {
168 G4double xxPplKmn = ((-1 + e)*(e*(-2 + gamma)*gmo + gamma))/(4*e*gpo32*std::sqrt(1 + e2*gmo + gamma - 2*e*gamma));
169 G4double xyPplKmn = 0;
170 G4double xzPplKmn = (-1 + e*gmo + gmo*gamma)/(2*sqrttwo*gpo2* std::sqrt(e*(1 + e + gamma - e*gamma)));
171 G4double yxPplKmn = 0;
172 G4double yyPplKmn = (-1 - 2*gamma + e*gmo*(3 + gamma))/(4*e*gpo2);
173 G4double yzPplKmn = 0;
174 G4double zxPplKmn = (1 + 2*e2*gmo2 + gamma + gamma2 + e*(1 + (3 - 4*gamma)*gamma))/
175 (2*sqrttwo*gpo2*std::sqrt(e*(1 + e + gamma - e*gamma)));
176 G4double zyPplKmn = 0;
177 G4double zzPplKmn = -(std::sqrt((1 - e)/(e - e*gamma2 + gpo2))*
178 (2*e2*gmo2 + gamma + 2*gamma2 + e*(2 + gamma - 3*gamma2)))/(4*e*gpo);
179
180 phi2[0] += xxPplKmn*pol1.x() + xyPplKmn*pol1.y() + xzPplKmn*pol1.z();
181 phi2[1] += yxPplKmn*pol1.x() + yyPplKmn*pol1.y() + yzPplKmn*pol1.z();
182 phi2[2] += zxPplKmn*pol1.x() + zyPplKmn*pol1.y() + zzPplKmn*pol1.z();
183 }
184//
185// Final Electron Pmn
186//
187 // initial positron Kpl
188 if (!pol0.IsZero()) {
189 G4double xxPmnKpl = ((-1 + e*gmo)*(2 + gamma))/(4*gpo* std::sqrt(e*(2 + e*gmo)*gpo));
190 G4double xyPmnKpl = 0;
191 G4double xzPmnKpl = (std::sqrt((-1 + e)/(-2 + e - e*gamma))*
192 (e + gamma + e*gamma - 2*(-1 + e)*gamma2))/(2*sqrttwo*e*gpo2);
193 G4double yxPmnKpl = 0;
194 G4double yyPmnKpl = (-1 - 2*gamma + e*gmo*(3 + gamma))/(4*e*gpo2);
195 G4double yzPmnKpl = 0;
196 G4double zxPmnKpl = -((-1 + e)*(1 + 2*e*gmo)*(e*gmo - gamma))/
197 (2*sqrttwo*e*std::sqrt(-((-1 + e)*(2 + e*gmo)))*gpo2);
198 G4double zyPmnKpl = 0;
199 G4double zzPmnKpl = (-2 + 2*e2*gmo2 + gamma*(-1 + 2*gamma) +
200 e*(-2 + (5 - 3*gamma)*gamma))/(4*std::sqrt(e*(2 + e*gmo))* gpo32);
201
202 phi3[0] += xxPmnKpl*pol0.x() + xyPmnKpl*pol0.y() + xzPmnKpl*pol0.z();
203 phi3[1] += yxPmnKpl*pol0.x() + yyPmnKpl*pol0.y() + yzPmnKpl*pol0.z();
204 phi3[2] += zxPmnKpl*pol0.x() + zyPmnKpl*pol0.y() + zzPmnKpl*pol0.z();
205 }
206 // initial electron Kmn
207 if (!pol1.IsZero()) {
208 G4double xxPmnKmn = -((2 + e*gmo)*(-1 + e*gmo - gamma)*(e*gmo - gamma)*
209 (-2 + gamma))/(4*gmo*egmp32);
210 G4double xyPmnKmn = 0;
211 G4double xzPmnKmn = ((e*gmo - gamma)*
212 std::sqrt((-1 + e + gamma - e*gamma)/(2 + e*gmo))*
213 (e + gamma - e*gamma + gamma2))/
214 (2*sqrttwo*e2*gmo32*gpo2);
215 G4double yxPmnKmn = 0;
216 G4double yyPmnKmn = (gamma2*gpo + e2*gmo2*(3 + gamma) -
217 e*gmo*(1 + 2*gamma*(2 + gamma)))/(4*e2*gmo*gpo2);
218 G4double yzPmnKmn = 0;
219 G4double zxPmnKmn = -((-1 + e)*(e*gmo - gamma)*(e*gmo + 2*e2*gmo2 - gamma*gpo))/
220 (2*sqrttwo*e2*std::sqrt(-((-1 + e)*(2 + e*gmo)))* gmo*gpo2);
221 G4double zyPmnKmn = 0;
222 G4double zzPmnKmn = ((e*gmo - gamma)*std::sqrt(e/((2 + e*gmo)*gpo))*
223 (-(e*(-2 + gamma)*gmo) + 2*e2*gmo2 + (-2 + gamma)*gpo))/(4*e2*(-1 + gamma2));
224
225 phi3[0] += xxPmnKmn*pol1.x() + xyPmnKmn*pol1.y() + xzPmnKmn*pol1.z();
226 phi3[1] += yxPmnKmn*pol1.x() + yyPmnKmn*pol1.y() + yzPmnKmn*pol1.z();
227 phi3[2] += zxPmnKmn*pol1.x() + zyPmnKmn*pol1.y() + zzPmnKmn*pol1.z();
228 }
229 }
230 phi0 *= pref;
231 phi2 *= pref;
232 phi3 *= pref;
233
234}
235
236G4double G4PolarizedBhabhaCrossSection::XSection(const G4StokesVector & pol2,
237 const G4StokesVector & pol3)
238{
239 G4double xs=0.;
240 xs+=phi0;
241
242 G4bool polarized=(!pol2.IsZero())||(!pol3.IsZero());
243 if (polarized) {
244 xs+=phi2*pol2 + phi3*pol3;
245 }
246 return xs;
247}
248
249G4double G4PolarizedBhabhaCrossSection::TotalXSection(
250 G4double xmin, G4double xmax, G4double gamma,
251 const G4StokesVector & pol0,const G4StokesVector & pol1)
252{
253 G4double xs=0.;
254
255 G4double x=xmin;
256
257 if (xmax != 1.) G4cout<<" warning xmax expected to be 1 but is "<<xmax<< G4endl;
258
259 // re -> electron radius^2;
260 G4double re2 = classic_electr_radius * classic_electr_radius;
261 G4double gamma2=gamma*gamma;
262 G4double gmo2 = (gamma - 1.)*(gamma - 1.);
263 G4double gpo2 = (gamma + 1.)*(gamma + 1.);
264 G4double gpo3 = gpo2*(gamma + 1.);
265 G4double logMEM = std::log(x);
266 G4double pref = twopi*re2/(gamma - 1.0);
267 // unpolarise XS
268 G4double sigma0 = 0.;
269 sigma0 += -gmo2*(gamma - 1.)*x*x*x/3. + gmo2*gamma*x*x;
270 sigma0 += -(gamma - 1.)*(3.*gamma*(gamma + 2.) +4.)*x;
271 sigma0 += (gamma*(gamma*(gamma*(4.*gamma - 1.) - 21.) - 7.)+13.)/(3.*(gamma - 1.));
272 sigma0 /= gpo3;
273 sigma0 += logMEM*(2. - 1./gpo2);
274 sigma0 += gamma2/((gamma2 - 1.)*x);
275 // longitudinal part
276 G4double sigma2=0.;
277 sigma2 += logMEM*gamma*(gamma + 1.)*(2.*gamma + 1.);
278 sigma2 += gamma*(7.*gamma*(gamma + 1.) - 2.)/3.;
279 sigma2 += -(3.*gamma + 1.)*(gamma2 + gamma - 1.)*x;
280 sigma2 += (gamma - 1.)*gamma*(gamma + 3.)*x*x;
281 sigma2 += -gmo2*(gamma + 3.)*x*x*x/3.;
282 sigma2 /= gpo3;
283 // transverse part
284 G4double sigma3=0.;
285 sigma3 += 0.5*(gamma + 1.)*(3.*gamma + 1.)*logMEM;
286 sigma3 += (gamma*(5.*gamma - 4.) - 13.)/6.;
287 sigma3 += 0.5*(gamma2 + 3.)*x;
288 sigma3 += - 2.*(gamma - 1.)*gamma*x*x; // *AS* changed sign
289 sigma3 += 2.*gmo2*x*x*x/3.;
290 sigma3 /= gpo3;
291 // total cross section
292 xs+=pref*(sigma0 + sigma2*pol0.z()*pol1.z() + sigma3*(pol0.x()*pol1.x()+pol0.y()*pol1.y()));
293
294 return xs;
295}
296
297
298G4StokesVector G4PolarizedBhabhaCrossSection::GetPol2()
299{
300 // Note, mean polarization can not contain correlation
301 // effects.
302 return 1./phi0 * phi2;
303}
304G4StokesVector G4PolarizedBhabhaCrossSection::GetPol3()
305{
306 // Note, mean polarization can not contain correlation
307 // effects.
308 return 1./phi0 * phi3;
309}
G4ThreeVector
CLHEP::Hep3Vector G4ThreeVector
Definition: G4ThreeVector.hh:42
G4double
double G4double
Definition: G4Types.hh:64
G4int
int G4int
Definition: G4Types.hh:66
G4bool
bool G4bool
Definition: G4Types.hh:67
G4endl
#define G4endl
Definition: G4ios.hh:52
G4cout
G4DLLIMPORT std::ostream G4cout
CLHEP::Hep3Vector::z
double z() const
CLHEP::Hep3Vector::x
double x() const
CLHEP::Hep3Vector::y
double y() const
G4PolarizedBhabhaCrossSection::TotalXSection
G4double TotalXSection(G4double xmin, G4double xmax, G4double y, const G4StokesVector &pol0, const G4StokesVector &pol1)
Definition: G4PolarizedBhabhaCrossSection.cc:249
G4PolarizedBhabhaCrossSection::XSection
G4double XSection(const G4StokesVector &pol2, const G4StokesVector &pol3)
Definition: G4PolarizedBhabhaCrossSection.cc:236
G4PolarizedBhabhaCrossSection::Initialize
void Initialize(G4double x, G4double y, G4double phi, const G4StokesVector &p0, const G4StokesVector &p1, G4int flag=0)
Definition: G4PolarizedBhabhaCrossSection.cc:62
G4StokesVector::IsZero
G4bool IsZero() const
Definition: G4StokesVector.hh:78