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 | // |
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27 | // $Id: G4DELPHIMagField.cc,v 1.4 2006/06/29 18:26:54 gunter Exp $ |
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28 | // GEANT4 tag $Name: HEAD $ |
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29 | // |
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30 | |
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31 | #include "G4DELPHIMagField.hh" |
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32 | #include "globals.hh" |
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33 | #include "geomdefs.hh" |
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34 | |
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35 | G4DELPHIMagField::G4DELPHIMagField() |
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36 | { |
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37 | ; |
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38 | } |
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39 | // -------------------------------------------------------------------------- |
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40 | |
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41 | G4DELPHIMagField::~G4DELPHIMagField() |
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42 | { |
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43 | ; |
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44 | } |
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45 | |
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46 | // ------------------------------------------------------------------------ |
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47 | |
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48 | |
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49 | void |
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50 | G4DELPHIMagField::GetFieldValue (const G4double yTrack[4], |
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51 | G4double *B ) const |
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52 | { |
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53 | G4int i, n = 8 ; |
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54 | G4double a = 0.001 ; // mm -> m |
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55 | G4double x = a*yTrack[0], y = a*yTrack[1], z = a*yTrack[2] ; |
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56 | G4double x2 = x*x, y2 = y*y, z2 = z*z, r2 = x2 + y2 ; |
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57 | G4double r4 = r2*r2, z4 = z2*z2, r6 = r4*r2, z6 = z4*z2 ; |
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58 | G4double r8 = r4*r4, z8 = z4*z4, r10 = r8*r2, z10 = z8*z2 ; |
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59 | G4double r12 = r6*r6, z12 = z6*z6, r14 = r8*r6, z14 = z8*z6 ; |
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60 | G4double rz = z*std::sqrt(r2), r = std::sqrt(r2+a*a) ; |
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61 | G4double Br ; |
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62 | G4double P[8], Q[8] ; |
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63 | static G4double c[8] = { |
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64 | -9.26e-5, -3.51e-5, 2.94e-6, -1.10e-6, |
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65 | 6.25e-8, -1.77e-8, -6.88e-10, -7.52e-11 |
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66 | } ; |
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67 | P[0] = 2*rz ; |
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68 | P[1] = 4*rz*(r2 - 4.0*z2/3.0) ; |
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69 | P[2] = 6*rz*(r4 - 4*r2*z2 + 1.6*z4) ; |
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70 | P[3] = 8*rz*(r6 - 8*r4*z2 + 9.6*r2*z4 - 64.0*z6/35.0) ; |
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71 | P[4] = 10*rz*(r8 - 40.0*r6*z2/3.0 + 32*r4*z4 - 128.0*r2*z6/7.0 + 128.0*z8/63.0); |
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72 | P[5] = 0 ; |
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73 | P[6] = 0 ; |
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74 | P[7] = 0 ; |
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75 | |
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76 | Q[0] = r2 - 2*z2 ; |
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77 | Q[1] = r4 - 8*r2*z2 + 8.0*z4/3.0 ; |
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78 | Q[2] = r6 - 18*r4*z2 + 24*r2*z4 - 3.2*z6 ; |
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79 | Q[3] = r8 - 32*r6*z2 + 96*r4*z4 - 51.2*r2*z6 +128.0*z8/35.0 ; |
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80 | Q[4] = r10 - 50*r8*z2 + 800.0*r6*z4/3.0 - 320*r4*z6 |
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81 | + 640.0*r2*z8/7.0 - 256.0*z10/63.0 ; |
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82 | Q[5] = 0 ; |
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83 | Q[6] = 0 ; |
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84 | Q[7] = 0 ; |
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85 | |
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86 | Br = 0 ; |
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87 | B[2] = 1.2*tesla ; // the principal Bz value of DELPHI detector |
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88 | for(i=0;i<n;i++) |
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89 | { |
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90 | Br += c[i]*P[i] ; |
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91 | B[2] += c[i]*Q[i] ; |
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92 | } |
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93 | B[0] = Br*x/r ; |
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94 | B[1] = Br*y/r ; |
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95 | return ; |
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96 | } |
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97 | |
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98 | // ----------------------------------------------------------------- |
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