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25 // 25 //
26 // Geant4 Class file 26 // Geant4 Class file
27 // 27 //
28 // File name: G4PolarizationHelper 28 // File name: G4PolarizationHelper
29 // 29 //
30 // Author: Andreas Schaelicke 30 // Author: Andreas Schaelicke
31 // 31 //
32 // Class Description: 32 // Class Description:
33 // Provides some basic polarization transfor 33 // Provides some basic polarization transformation routines.
34 34
35 #include "G4PolarizationHelper.hh" 35 #include "G4PolarizationHelper.hh"
36 36
37 #include "G4PhysicalConstants.hh" 37 #include "G4PhysicalConstants.hh"
38 #include "G4StokesVector.hh" 38 #include "G4StokesVector.hh"
39 #include "Randomize.hh" 39 #include "Randomize.hh"
40 40
41 G4ThreeVector G4PolarizationHelper::GetFrame(c 41 G4ThreeVector G4PolarizationHelper::GetFrame(const G4ThreeVector& mom1,
42 c 42 const G4ThreeVector& mom2)
43 { 43 {
44 G4ThreeVector normal = (mom1.cross(mom2)).un 44 G4ThreeVector normal = (mom1.cross(mom2)).unit();
45 return normal; 45 return normal;
46 } 46 }
47 47
48 G4ThreeVector G4PolarizationHelper::GetParticl 48 G4ThreeVector G4PolarizationHelper::GetParticleFrameY(const G4ThreeVector& uZ)
49 { 49 {
50 if(uZ.x() == 0. && uZ.y() == 0.) 50 if(uZ.x() == 0. && uZ.y() == 0.)
51 { 51 {
52 return G4ThreeVector(0., 1., 0.); 52 return G4ThreeVector(0., 1., 0.);
53 } 53 }
54 54
55 G4double invPerp = 1. / std::sqrt(sqr(uZ.x() 55 G4double invPerp = 1. / std::sqrt(sqr(uZ.x()) + sqr(uZ.y()));
56 return G4ThreeVector(-uZ.y() * invPerp, uZ.x 56 return G4ThreeVector(-uZ.y() * invPerp, uZ.x() * invPerp, 0);
57 } 57 }
58 58
59 G4ThreeVector G4PolarizationHelper::GetParticl 59 G4ThreeVector G4PolarizationHelper::GetParticleFrameX(const G4ThreeVector& uZ)
60 { 60 {
61 if(uZ.x() == 0. && uZ.y() == 0.) 61 if(uZ.x() == 0. && uZ.y() == 0.)
62 { 62 {
63 if(uZ.z() >= 0.) 63 if(uZ.z() >= 0.)
64 return G4ThreeVector(1., 0., 0.); 64 return G4ThreeVector(1., 0., 0.);
65 return G4ThreeVector(-1., 0., 0.); 65 return G4ThreeVector(-1., 0., 0.);
66 } 66 }
67 67
68 G4double perp = std::sqrt(sqr(uZ.x()) + s 68 G4double perp = std::sqrt(sqr(uZ.x()) + sqr(uZ.y()));
69 G4double invPerp = uZ.z() / perp; 69 G4double invPerp = uZ.z() / perp;
70 return G4ThreeVector(uZ.x() * invPerp, uZ.y( 70 return G4ThreeVector(uZ.x() * invPerp, uZ.y() * invPerp, -perp);
71 } 71 }
72 72
73 G4ThreeVector G4PolarizationHelper::GetRandomF 73 G4ThreeVector G4PolarizationHelper::GetRandomFrame(const G4ThreeVector& mom1)
74 { 74 {
75 G4double phi = 2. * pi * G4UniformRand(); 75 G4double phi = 2. * pi * G4UniformRand();
76 G4ThreeVector normal = 76 G4ThreeVector normal =
77 std::cos(phi) * GetParticleFrameX(mom1) + 77 std::cos(phi) * GetParticleFrameX(mom1) +
78 std::sin(phi) * G4PolarizationHelper::GetP 78 std::sin(phi) * G4PolarizationHelper::GetParticleFrameY(mom1);
79 return normal; 79 return normal;
80 } 80 }
81 81
82 G4ThreeVector G4PolarizationHelper::GetSpinInP 82 G4ThreeVector G4PolarizationHelper::GetSpinInPRF(const G4ThreeVector& uZ,
83 83 const G4ThreeVector& spin)
84 { 84 {
85 if(uZ.x() == 0. && uZ.y() == 0.) 85 if(uZ.x() == 0. && uZ.y() == 0.)
86 { 86 {
87 if(uZ.z() >= 0.) 87 if(uZ.z() >= 0.)
88 return spin; 88 return spin;
89 return G4ThreeVector(-spin.x(), spin.y(), 89 return G4ThreeVector(-spin.x(), spin.y(), -spin.z());
90 } 90 }
91 91
92 G4double perp = std::sqrt(sqr(uZ.x()) + s 92 G4double perp = std::sqrt(sqr(uZ.x()) + sqr(uZ.y()));
93 G4double invPerp = 1. / perp; 93 G4double invPerp = 1. / perp;
94 94
95 G4ThreeVector uX(uZ.x() * uZ.z() * invPerp, 95 G4ThreeVector uX(uZ.x() * uZ.z() * invPerp, uZ.y() * uZ.z() * invPerp, -perp);
96 G4ThreeVector uY(-uZ.y() * invPerp, uZ.x() * 96 G4ThreeVector uY(-uZ.y() * invPerp, uZ.x() * invPerp, 0);
97 97
98 return G4ThreeVector(spin * uX, spin * uY, s 98 return G4ThreeVector(spin * uX, spin * uY, spin * uZ);
99 } 99 }
100 100
101 void G4PolarizationHelper::TestPolarizationTra 101 void G4PolarizationHelper::TestPolarizationTransformations()
102 { 102 {
103 G4double theta = 0.; 103 G4double theta = 0.;
104 G4cout << "================================= 104 G4cout << "========================================\n\n";
105 for(G4int i = 0; i <= 10; ++i) 105 for(G4int i = 0; i <= 10; ++i)
106 { 106 {
107 theta = pi * i / 10.; 107 theta = pi * i / 10.;
108 G4ThreeVector zAxis = G4ThreeVector(std::s 108 G4ThreeVector zAxis = G4ThreeVector(std::sin(theta), 0., std::cos(theta));
109 if(i == 5) 109 if(i == 5)
110 zAxis = G4ThreeVector(1., 0., 0.); 110 zAxis = G4ThreeVector(1., 0., 0.);
111 if(i == 10) 111 if(i == 10)
112 zAxis = G4ThreeVector(0., 0., -1.); 112 zAxis = G4ThreeVector(0., 0., -1.);
113 G4ThreeVector yAxis = GetParticleFrameY(zA 113 G4ThreeVector yAxis = GetParticleFrameY(zAxis);
114 114
115 G4cout << zAxis << " " << zAxis.mag() << " 115 G4cout << zAxis << " " << zAxis.mag() << "\n";
116 G4cout << yAxis << " " << yAxis.mag() << " 116 G4cout << yAxis << " " << yAxis.mag() << "\n";
117 G4ThreeVector xAxis = yAxis.cross(zAxis); 117 G4ThreeVector xAxis = yAxis.cross(zAxis);
118 G4cout << xAxis << " " << xAxis.mag() << " 118 G4cout << xAxis << " " << xAxis.mag() << "\n\n";
119 } 119 }
120 120
121 G4cout << "================================= 121 G4cout << "========================================\n\n";
122 122
123 for(G4int i = 0; i <= 10; ++i) 123 for(G4int i = 0; i <= 10; ++i)
124 { 124 {
125 theta = pi * i / 10.; 125 theta = pi * i / 10.;
126 G4ThreeVector zAxis = G4ThreeVector(0., st 126 G4ThreeVector zAxis = G4ThreeVector(0., std::sin(theta), std::cos(theta));
127 if(i == 5) 127 if(i == 5)
128 zAxis = G4ThreeVector(0., 1., 0.); 128 zAxis = G4ThreeVector(0., 1., 0.);
129 if(i == 10) 129 if(i == 10)
130 zAxis = G4ThreeVector(0., 0., -1.); 130 zAxis = G4ThreeVector(0., 0., -1.);
131 G4ThreeVector yAxis = GetParticleFrameY(zA 131 G4ThreeVector yAxis = GetParticleFrameY(zAxis);
132 132
133 G4cout << zAxis << " " << zAxis.mag() << " 133 G4cout << zAxis << " " << zAxis.mag() << "\n";
134 G4cout << yAxis << " " << yAxis.mag() << " 134 G4cout << yAxis << " " << yAxis.mag() << "\n";
135 G4ThreeVector xAxis = yAxis.cross(zAxis); 135 G4ThreeVector xAxis = yAxis.cross(zAxis);
136 G4cout << xAxis << " " << xAxis.mag() << " 136 G4cout << xAxis << " " << xAxis.mag() << "\n\n";
137 137
138 G4cout << "spat : " << xAxis * yAxis.cross 138 G4cout << "spat : " << xAxis * yAxis.cross(zAxis) << "\n\n";
139 } 139 }
140 G4cout << "================================= 140 G4cout << "========================================\n\n";
141 } 141 }
142 142
143 void G4PolarizationHelper::TestInteractionFram 143 void G4PolarizationHelper::TestInteractionFrame()
144 { 144 {
145 // check transformation procedure for polari 145 // check transformation procedure for polarisation transfer
146 // calculation in scattering processes 146 // calculation in scattering processes
147 // a) transfer target polarisation in beam 147 // a) transfer target polarisation in beam particle reference frame (PRF)
148 // b) calc correct asymmetry w.r.t. scatter 148 // b) calc correct asymmetry w.r.t. scattering plane
149 // c) determine incoming polarisation in in 149 // c) determine incoming polarisation in interaction frame (IF)
150 // d) transfer outgoing polarisation from I 150 // d) transfer outgoing polarisation from IF to PRF
151 G4cout << "================================= 151 G4cout << "========================================\n\n";
152 152
153 G4double theta = 0.; 153 G4double theta = 0.;
154 154
155 G4ThreeVector dir0 = G4ThreeVector(0., 0., 1 155 G4ThreeVector dir0 = G4ThreeVector(0., 0., 1.);
156 G4ThreeVector dir2 = G4ThreeVector(std::sin( 156 G4ThreeVector dir2 = G4ThreeVector(std::sin(theta), 0., std::cos(theta));
157 157
158 G4StokesVector pol0 = G4StokesVector::P3; 158 G4StokesVector pol0 = G4StokesVector::P3;
159 G4StokesVector pol1 = G4StokesVector::P3; 159 G4StokesVector pol1 = G4StokesVector::P3;
160 160
161 pol1.rotateUz(dir0); 161 pol1.rotateUz(dir0);
162 162
163 G4cout << "================================= 163 G4cout << "========================================\n\n";
164 } 164 }
165 165