[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 | // @hpw@ misses the sampling of two breit wigner in a corelated fashion, |
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| 27 | // @hpw@ to be usefull for resonance resonance scattering. |
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| 28 | |
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| 29 | #include <typeinfo> |
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| 30 | #include "globals.hh" |
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| 31 | #include "G4VScatteringCollision.hh" |
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| 32 | #include "G4KineticTrack.hh" |
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| 33 | #include "G4VCrossSectionSource.hh" |
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| 34 | #include "G4Proton.hh" |
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| 35 | #include "G4Neutron.hh" |
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| 36 | #include "G4XNNElastic.hh" |
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| 37 | #include "G4AngularDistribution.hh" |
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| 38 | #include "G4ThreeVector.hh" |
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| 39 | #include "G4LorentzVector.hh" |
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| 40 | #include "G4LorentzRotation.hh" |
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| 41 | #include "G4KineticTrackVector.hh" |
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| 42 | #include "Randomize.hh" |
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| 43 | #include "G4PionPlus.hh" |
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| 44 | |
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| 45 | G4VScatteringCollision::G4VScatteringCollision() |
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| 46 | { |
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| 47 | theAngularDistribution = new G4AngularDistribution(true); |
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| 48 | } |
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| 49 | |
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| 50 | |
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| 51 | G4VScatteringCollision::~G4VScatteringCollision() |
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| 52 | { |
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| 53 | delete theAngularDistribution; |
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| 54 | } |
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| 55 | |
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| 56 | |
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| 57 | G4KineticTrackVector* G4VScatteringCollision::FinalState(const G4KineticTrack& trk1, |
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| 58 | const G4KineticTrack& trk2) const |
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| 59 | { |
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| 60 | const G4VAngularDistribution* angDistribution = GetAngularDistribution(); |
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| 61 | G4LorentzVector p = trk1.Get4Momentum() + trk2.Get4Momentum(); |
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| 62 | G4double sqrtS = p.m(); |
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| 63 | G4double s = sqrtS * sqrtS; |
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| 64 | |
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| 65 | G4double m1 = trk1.GetActualMass(); |
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| 66 | G4double m2 = trk2.GetActualMass(); |
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| 67 | |
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| 68 | std::vector<const G4ParticleDefinition*> OutputDefinitions = GetOutgoingParticles(); |
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| 69 | if (OutputDefinitions.size() != 2) |
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| 70 | throw G4HadronicException(__FILE__, __LINE__, "G4VScatteringCollision: Too many output particles!"); |
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| 71 | |
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| 72 | if (OutputDefinitions[0]->IsShortLived() && OutputDefinitions[1]->IsShortLived()) |
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| 73 | { |
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| 74 | if(getenv("G4KCDEBUG")) G4cerr << "two shortlived for Type = "<<typeid(*this).name()<<G4endl; |
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| 75 | // throw G4HadronicException(__FILE__, __LINE__, "G4VScatteringCollision: can't handle two shortlived particles!"); // @hpw@ |
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| 76 | } |
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| 77 | |
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| 78 | G4double outm1 = OutputDefinitions[0]->GetPDGMass(); |
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| 79 | G4double outm2 = OutputDefinitions[1]->GetPDGMass(); |
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| 80 | |
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| 81 | if (OutputDefinitions[0]->IsShortLived()) |
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| 82 | { |
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| 83 | outm1 = SampleResonanceMass(outm1, |
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| 84 | OutputDefinitions[0]->GetPDGWidth(), |
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| 85 | G4Neutron::NeutronDefinition()->GetPDGMass()+G4PionPlus::PionPlus()->GetPDGMass(), |
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| 86 | sqrtS-(G4Neutron::NeutronDefinition()->GetPDGMass()+G4PionPlus::PionPlus()->GetPDGMass())); |
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| 87 | |
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| 88 | } |
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| 89 | if (OutputDefinitions[1]->IsShortLived()) |
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| 90 | { |
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| 91 | outm2 = SampleResonanceMass(outm2, OutputDefinitions[1]->GetPDGWidth(), |
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| 92 | G4Neutron::NeutronDefinition()->GetPDGMass()+G4PionPlus::PionPlus()->GetPDGMass(), |
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| 93 | sqrtS-outm1); |
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| 94 | } |
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| 95 | |
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| 96 | // Angles of outgoing particles |
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| 97 | G4double cosTheta = angDistribution->CosTheta(s,m1,m2); |
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| 98 | G4double phi = angDistribution->Phi(); |
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| 99 | |
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| 100 | // Unit vector of three-momentum |
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| 101 | G4LorentzRotation fromCMSFrame(p.boostVector()); |
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| 102 | G4LorentzRotation toCMSFrame(fromCMSFrame.inverse()); |
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| 103 | G4LorentzVector TempPtr = toCMSFrame*trk1.Get4Momentum(); |
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| 104 | G4LorentzRotation toZ; |
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| 105 | toZ.rotateZ(-1*TempPtr.phi()); |
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| 106 | toZ.rotateY(-1*TempPtr.theta()); |
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| 107 | G4LorentzRotation toCMS(toZ.inverse()); |
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| 108 | |
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| 109 | G4ThreeVector pFinal1(std::sin(std::acos(cosTheta))*std::cos(phi), std::sin(std::acos(cosTheta))*std::sin(phi), cosTheta); |
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| 110 | |
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| 111 | // Three momentum in cm system |
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| 112 | G4double pCM = std::sqrt( (s-(outm1+outm2)*(outm1+outm2)) * (s-(outm1-outm2)*(outm1-outm2)) /(4.*s)); |
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| 113 | pFinal1 = pFinal1 * pCM; |
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| 114 | G4ThreeVector pFinal2 = -pFinal1; |
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| 115 | |
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| 116 | G4double eFinal1 = std::sqrt(pFinal1.mag2() + outm1*outm1); |
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| 117 | G4double eFinal2 = std::sqrt(pFinal2.mag2() + outm2*outm2); |
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| 118 | |
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| 119 | G4LorentzVector p4Final1(pFinal1, eFinal1); |
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| 120 | G4LorentzVector p4Final2(pFinal2, eFinal2); |
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| 121 | p4Final1 = toCMS*p4Final1; |
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| 122 | p4Final2 = toCMS*p4Final2; |
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| 123 | |
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| 124 | |
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| 125 | // Lorentz transformation |
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| 126 | G4LorentzRotation toLabFrame(p.boostVector()); |
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| 127 | p4Final1 *= toLabFrame; |
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| 128 | p4Final2 *= toLabFrame; |
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| 129 | |
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| 130 | // Final tracks are copies of incoming ones, with modified 4-momenta |
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| 131 | |
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| 132 | G4double chargeBalance = OutputDefinitions[0]->GetPDGCharge()+OutputDefinitions[1]->GetPDGCharge(); |
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| 133 | chargeBalance-= trk1.GetDefinition()->GetPDGCharge(); |
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| 134 | chargeBalance-= trk2.GetDefinition()->GetPDGCharge(); |
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| 135 | if(std::abs(chargeBalance) >.1) |
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| 136 | { |
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| 137 | G4cout << "Charges in "<<typeid(*this).name()<<G4endl; |
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| 138 | G4cout << OutputDefinitions[0]->GetPDGCharge()<<" "<<OutputDefinitions[0]->GetParticleName() |
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| 139 | << OutputDefinitions[1]->GetPDGCharge()<<" "<<OutputDefinitions[1]->GetParticleName() |
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| 140 | << trk1.GetDefinition()->GetPDGCharge()<<" "<<trk1.GetDefinition()->GetParticleName() |
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| 141 | << trk2.GetDefinition()->GetPDGCharge()<<" "<<trk2.GetDefinition()->GetParticleName()<<G4endl; |
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| 142 | } |
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| 143 | G4KineticTrack* final1 = new G4KineticTrack(const_cast<G4ParticleDefinition *>(OutputDefinitions[0]), 0.0, |
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| 144 | trk1.GetPosition(), p4Final1); |
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| 145 | G4KineticTrack* final2 = new G4KineticTrack(const_cast<G4ParticleDefinition *>(OutputDefinitions[1]), 0.0, |
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| 146 | trk2.GetPosition(), p4Final2); |
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| 147 | |
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| 148 | G4KineticTrackVector* finalTracks = new G4KineticTrackVector; |
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| 149 | |
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| 150 | finalTracks->push_back(final1); |
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| 151 | finalTracks->push_back(final2); |
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| 152 | |
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| 153 | return finalTracks; |
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| 154 | } |
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| 155 | |
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| 156 | |
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| 157 | |
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| 158 | double G4VScatteringCollision::SampleResonanceMass(const double poleMass, |
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| 159 | const double gamma, |
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| 160 | const double aMinMass, |
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| 161 | const double maxMass) const |
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| 162 | { |
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| 163 | // Chooses a mass randomly between minMass and maxMass |
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| 164 | // according to a Breit-Wigner function with constant |
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| 165 | // width gamma and pole poleMass |
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| 166 | |
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| 167 | G4double minMass = aMinMass; |
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| 168 | if (minMass > maxMass) G4cerr << "##################### SampleResonanceMass: particle out of mass range" << G4endl; |
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| 169 | if(minMass > maxMass) minMass -= G4PionPlus::PionPlus()->GetPDGMass(); |
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| 170 | if(minMass > maxMass) minMass = 0; |
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| 171 | |
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| 172 | if (gamma < 1E-10*GeV) |
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| 173 | return std::max(minMass,std::min(maxMass, poleMass)); |
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| 174 | else { |
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| 175 | double fmin = BrWigInt0(minMass, gamma, poleMass); |
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| 176 | double fmax = BrWigInt0(maxMass, gamma, poleMass); |
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| 177 | double f = fmin + (fmax-fmin)*G4UniformRand(); |
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| 178 | return BrWigInv(f, gamma, poleMass); |
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| 179 | } |
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| 180 | } |
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