[1199] | 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 | // -- Bogus -- BaBar Object-Oriented Geant-based Unified Simulation |
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| 28 | // |
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| 29 | // NTSTLooperDeath |
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| 30 | // |
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| 31 | // Description: |
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| 32 | // This is a simple GEANT4 process that destroys any particle below |
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| 33 | // the specified total kinetic energy that reverse direction (loops 180 |
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| 34 | // degress) in the x/y plane. |
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| 35 | // |
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| 36 | // Based on BgsChargedLowEnergyDeath |
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| 37 | // |
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| 38 | // Author List: |
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| 39 | // David Williams |
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| 40 | // |
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| 41 | // Modification History: |
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| 42 | // |
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| 43 | //----------------------------------------------------------------------------- |
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| 44 | |
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| 45 | #include "NTSTLooperDeath.hh" |
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| 46 | |
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| 47 | #include "G4TransportationManager.hh" |
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| 48 | #include "G4FieldManager.hh" |
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| 49 | #include "G4MagneticField.hh" |
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| 50 | |
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| 51 | // |
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| 52 | // Constructor |
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| 53 | // |
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| 54 | NTSTLooperDeath::NTSTLooperDeath( G4double theMinMomentum, |
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| 55 | const char* name, |
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| 56 | G4ProcessType type ) |
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| 57 | : G4VProcess( name, type ), minMomentum( theMinMomentum ) |
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| 58 | {;} |
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| 59 | |
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| 60 | NTSTLooperDeath::~NTSTLooperDeath(){;} |
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| 61 | // |
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| 62 | // PostStepGetPhysicalInteractionLength |
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| 63 | // |
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| 64 | G4double NTSTLooperDeath::PostStepGetPhysicalInteractionLength( |
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| 65 | const G4Track& track, |
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| 66 | G4double , // previousStepSize, |
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| 67 | G4ForceCondition* condition ) |
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| 68 | { |
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| 69 | const G4DynamicParticle *particle = track.GetDynamicParticle(); |
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| 70 | |
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| 71 | *condition = NotForced; |
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| 72 | |
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| 73 | // |
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| 74 | // We don't touch any particle above the cut momentum |
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| 75 | // |
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| 76 | if (particle->GetTotalMomentum() > minMomentum) return DBL_MAX; |
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| 77 | |
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| 78 | // |
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| 79 | // Nor do we touch any particle with small transverse component |
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| 80 | // to their momentum. Here the cutoff is somewhat arbitrary. |
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| 81 | // |
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| 82 | G4double vperp = track.GetMomentumDirection().perp(); |
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| 83 | if (vperp < 0.1) return DBL_MAX; |
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| 84 | |
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| 85 | // |
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| 86 | // How far in azimuthal angle do we need to go before the |
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| 87 | // particle loops back on itself? |
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| 88 | // |
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| 89 | G4ThreeVector initialDir(track.GetVertexMomentumDirection()); |
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| 90 | G4ThreeVector dx = track.GetPosition() - track.GetVertexPosition(); |
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| 91 | G4double dxPerp = dx.perp(); |
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| 92 | if (dxPerp < 1E-6) return DBL_MAX; |
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| 93 | |
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| 94 | G4double dot = ( initialDir.x()*dx.x() + initialDir.y()*dx.y() )/dxPerp; |
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| 95 | |
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| 96 | if (dot < 0) return 0; // Already done so |
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| 97 | |
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| 98 | G4double phi = pi - std::acos(dot); |
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| 99 | |
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| 100 | if (phi < 0) return 0; |
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| 101 | |
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| 102 | // |
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| 103 | // What is the radius of curvature? |
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| 104 | // |
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| 105 | // Only use the z component of the field to calculate this. |
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| 106 | // |
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| 107 | G4FieldManager *fieldManager = G4TransportationManager::GetTransportationManager()->GetFieldManager(); |
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| 108 | |
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| 109 | if (!fieldManager->DoesFieldExist()) return DBL_MAX; |
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| 110 | |
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| 111 | // |
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| 112 | // Assume the field is a magnetic field (i.e. returns |
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| 113 | // a vector of three doubles of unit Telsa). |
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| 114 | // |
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| 115 | // There is no good way I know to confirm this, so it is purely |
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| 116 | // a matter of faith. *** BEWARE *** |
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| 117 | // |
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| 118 | G4MagneticField *field = (G4MagneticField *)fieldManager->GetDetectorField(); |
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| 119 | G4double b[3]; |
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| 120 | G4ThreeVector pos(track.GetPosition()); |
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| 121 | G4double posv[3] = { pos.x(), pos.y(), pos.z() }; |
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| 122 | field->GetFieldValue( posv, b ); |
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| 123 | |
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| 124 | // |
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| 125 | // No field? Forget it! |
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| 126 | // |
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| 127 | if (std::fabs(b[2]) < 0.00001) return DBL_MAX; |
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| 128 | |
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| 129 | // |
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| 130 | // Calculate radius of curvature, the usual way. |
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| 131 | // Note G4 default units: mm, Telsa, MeV |
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| 132 | // |
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| 133 | // G4 suggestion: the constant below should be added to |
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| 134 | // the geant4 list. |
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| 135 | // |
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| 136 | G4double radius = std::fabs(track.GetMomentum().perp()/299.79251/b[2]); |
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| 137 | |
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| 138 | // |
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| 139 | // Convert this to a distance |
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| 140 | // |
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| 141 | return radius*phi/vperp; |
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| 142 | } |
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| 143 | |
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| 144 | |
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| 145 | // |
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| 146 | // PostStepDoit |
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| 147 | // |
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| 148 | G4VParticleChange * |
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| 149 | NTSTLooperDeath::PostStepDoIt( const G4Track &track, const G4Step & ) // step ) |
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| 150 | { |
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| 151 | pParticleChange->Initialize(track); |
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| 152 | |
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| 153 | // |
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| 154 | // This is a tough one. What should happen when we kill off a looper? |
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| 155 | // For now: just deposit remaining energy (including mass). |
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| 156 | // |
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| 157 | const G4DynamicParticle *particle = track.GetDynamicParticle(); |
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| 158 | G4double energyDeposited = particle->GetTotalEnergy(); |
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| 159 | |
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| 160 | pParticleChange->ProposeTrackStatus( fStopAndKill ); |
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| 161 | pParticleChange->SetNumberOfSecondaries( 0 ); |
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| 162 | pParticleChange->ProposeLocalEnergyDeposit( energyDeposited ); |
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| 163 | ClearNumberOfInteractionLengthLeft(); |
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| 164 | |
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| 165 | return pParticleChange; |
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| 166 | } |
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| 167 | |
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| 168 | |
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| 169 | |
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| 170 | |
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| 171 | |
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| 172 | |
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