[819] | 1 | // |
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| 2 | // ******************************************************************** |
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| 3 | // * License and Disclaimer * |
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| 4 | // * * |
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| 5 | // * The Geant4 software is copyright of the Copyright Holders of * |
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| 6 | // * the Geant4 Collaboration. It is provided under the terms and * |
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| 7 | // * conditions of the Geant4 Software License, included in the file * |
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| 8 | // * LICENSE and available at http://cern.ch/geant4/license . These * |
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| 9 | // * include a list of copyright holders. * |
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| 10 | // * * |
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| 11 | // * Neither the authors of this software system, nor their employing * |
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| 12 | // * institutes,nor the agencies providing financial support for this * |
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| 13 | // * work make any representation or warranty, express or implied, * |
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| 14 | // * regarding this software system or assume any liability for its * |
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| 15 | // * use. Please see the license in the file LICENSE and URL above * |
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| 16 | // * for the full disclaimer and the limitation of liability. * |
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| 17 | // * * |
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| 18 | // * This code implementation is the result of the scientific and * |
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| 19 | // * technical work of the GEANT4 collaboration. * |
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| 20 | // * By using, copying, modifying or distributing the software (or * |
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| 21 | // * any work based on the software) you agree to acknowledge its * |
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| 22 | // * use in resulting scientific publications, and indicate your * |
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| 23 | // * acceptance of all terms of the Geant4 Software license. * |
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| 24 | // ******************************************************************** |
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| 25 | // |
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| 26 | // $Id: G4PolarizationHelper.cc,v 1.4 2007/11/01 17:30:25 schaelic Exp $ |
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[1007] | 27 | // GEANT4 tag $Name: geant4-09-02 $ |
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[819] | 28 | // |
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| 29 | // GEANT4 Class file |
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| 30 | // |
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| 31 | // |
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| 32 | // File name: G4PolarizationHelper |
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| 33 | // |
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| 34 | // Author: Andreas Schaelicke |
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| 35 | // |
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| 36 | // Creation date: 12.08.2006 |
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| 37 | // |
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| 38 | // Modifications: |
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| 39 | // |
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| 40 | // Class Description: |
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| 41 | // |
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| 42 | // Provides some basic polarization transformation routines. |
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| 43 | // |
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| 44 | #include "G4PolarizationHelper.hh" |
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| 45 | #include "G4StokesVector.hh" |
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| 46 | |
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| 47 | |
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| 48 | G4ThreeVector G4PolarizationHelper::GetFrame(const G4ThreeVector & mom1, const G4ThreeVector & mom2) |
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| 49 | { |
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| 50 | G4ThreeVector normal = mom1.cross(mom2); |
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| 51 | return 1./normal.mag()*normal; |
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| 52 | } |
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| 53 | |
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| 54 | G4ThreeVector G4PolarizationHelper::GetParticleFrameY(const G4ThreeVector &uZ) |
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| 55 | { |
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| 56 | // compare also G4ThreeVector::rotateUz() |
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| 57 | |
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| 58 | if (uZ.x()==0. && uZ.y()==0.) { |
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| 59 | return G4ThreeVector(0.,1.,0.); |
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| 60 | } |
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| 61 | |
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| 62 | G4double invPerp = 1./std::sqrt(sqr(uZ.x())+sqr(uZ.y())); |
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| 63 | return G4ThreeVector(-uZ.y()*invPerp,uZ.x()*invPerp,0); |
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| 64 | } |
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| 65 | |
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| 66 | G4ThreeVector G4PolarizationHelper::GetParticleFrameX(const G4ThreeVector &uZ) |
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| 67 | { |
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| 68 | // compare also G4ThreeVector::rotateUz() |
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| 69 | |
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| 70 | if (uZ.x()==0. && uZ.y()==0.) { |
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| 71 | if (uZ.z()>=0.) return G4ThreeVector(1.,0.,0.); |
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| 72 | return G4ThreeVector(-1.,0.,0.); |
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| 73 | } |
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| 74 | |
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| 75 | G4double perp = std::sqrt(sqr(uZ.x())+sqr(uZ.y())); |
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| 76 | G4double invPerp = uZ.z()/perp; |
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| 77 | return G4ThreeVector(uZ.x()*invPerp,uZ.y()*invPerp,-perp); |
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| 78 | } |
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| 79 | |
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| 80 | G4ThreeVector G4PolarizationHelper::GetRandomFrame(const G4ThreeVector & mom1) |
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| 81 | { |
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| 82 | G4double phi =2.*pi*G4UniformRand(); |
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| 83 | G4ThreeVector normal = std::cos(phi)*GetParticleFrameX(mom1) |
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| 84 | + std::sin(phi)*G4PolarizationHelper::GetParticleFrameY(mom1); |
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| 85 | return normal; |
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| 86 | } |
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| 87 | |
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| 88 | |
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| 89 | G4ThreeVector G4PolarizationHelper::GetSpinInPRF(const G4ThreeVector &uZ, const G4ThreeVector & spin) |
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| 90 | { |
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| 91 | // compare also G4ThreeVector::rotateUz() |
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| 92 | |
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| 93 | if (uZ.x()==0. && uZ.y()==0.) { |
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| 94 | if (uZ.z()>=0.) return spin; |
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| 95 | return G4ThreeVector(-spin.x(),spin.y(),-spin.z()); |
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| 96 | } |
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| 97 | |
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| 98 | G4double perp = std::sqrt(sqr(uZ.x())+sqr(uZ.y())); |
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| 99 | G4double invPerp = uZ.z()/perp; |
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| 100 | |
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| 101 | G4ThreeVector uX(uZ.x()*invPerp,uZ.y()*invPerp,-perp); |
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| 102 | G4ThreeVector uY(-uZ.y()*invPerp,uZ.x()*invPerp,0); |
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| 103 | |
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| 104 | return G4ThreeVector(spin*uX,spin*uY,spin*uZ); |
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| 105 | } |
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| 106 | |
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| 107 | void G4PolarizationHelper::TestPolarizationTransformations() |
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| 108 | { |
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| 109 | G4double theta=0.; |
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| 110 | G4cout<<"========================================\n\n"; |
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| 111 | for (G4int i=0; i<=10; ++i) { |
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| 112 | theta=pi*i/10.; |
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| 113 | G4ThreeVector zAxis = G4ThreeVector(std::sin(theta),0.,std::cos(theta)); |
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| 114 | if (i==5) zAxis = G4ThreeVector(1.,0.,0.); |
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| 115 | if (i==10) zAxis = G4ThreeVector(0.,0.,-1.); |
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| 116 | G4ThreeVector yAxis = GetParticleFrameY(zAxis); |
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| 117 | |
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| 118 | G4cout<<zAxis<<" "<<zAxis.mag()<<"\n"; |
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| 119 | G4cout<<yAxis<<" "<<yAxis.mag()<<"\n"; |
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| 120 | G4ThreeVector xAxis = yAxis.cross(zAxis); |
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| 121 | G4cout<<xAxis<<" "<<xAxis.mag()<<"\n\n"; |
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| 122 | } |
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| 123 | |
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| 124 | G4cout<<"========================================\n\n"; |
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| 125 | |
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| 126 | for (G4int i=0; i<=10; ++i) { |
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| 127 | theta=pi*i/10.; |
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| 128 | G4ThreeVector zAxis = G4ThreeVector(0.,std::sin(theta),std::cos(theta)); |
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| 129 | if (i==5) zAxis = G4ThreeVector(0.,1.,0.); |
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| 130 | if (i==10) zAxis = G4ThreeVector(0.,0.,-1.); |
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| 131 | G4ThreeVector yAxis = GetParticleFrameY(zAxis); |
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| 132 | |
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| 133 | G4cout<<zAxis<<" "<<zAxis.mag()<<"\n"; |
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| 134 | G4cout<<yAxis<<" "<<yAxis.mag()<<"\n"; |
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| 135 | G4ThreeVector xAxis = yAxis.cross(zAxis); |
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| 136 | G4cout<<xAxis<<" "<<xAxis.mag()<<"\n\n"; |
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| 137 | } |
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| 138 | G4cout<<"========================================\n\n"; |
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| 139 | } |
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| 140 | |
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| 141 | void G4PolarizationHelper::TestInteractionFrame() |
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| 142 | { |
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| 143 | // check transformation procedure for polarisation transfer |
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| 144 | // calculation in scattering processes |
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| 145 | // a) transfer target polarisation in beam particle reference frame (PRF) |
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| 146 | // b) calc correct asymmetry w.r.t. scattering plane |
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| 147 | // c) determine incomming polarisation in interaction frame (IF) |
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| 148 | // d) transfer outgoing polarisation from IF to PRF |
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| 149 | G4cout<<"========================================\n\n"; |
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| 150 | |
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| 151 | G4double theta=0.; |
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| 152 | |
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| 153 | G4ThreeVector dir0=G4ThreeVector(0.,0.,1.); |
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| 154 | G4ThreeVector dir2=G4ThreeVector(std::sin(theta),0.,std::cos(theta)); |
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| 155 | |
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| 156 | G4StokesVector pol0=G4ThreeVector(0.,0.,1.); |
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| 157 | G4StokesVector pol1=G4ThreeVector(0.,0.,1.); |
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| 158 | |
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| 159 | pol1.rotateUz(dir0); |
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| 160 | |
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| 161 | G4cout<<"========================================\n\n"; |
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| 162 | |
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| 163 | |
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| 164 | } |
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