[824] | 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: G4TauLeptonicDecayChannel.cc,v 1.5 2006/06/29 19:26:18 gunter Exp $ |
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[992] | 28 | // GEANT4 tag $Name: geant4-09-02-ref-02 $ |
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[824] | 29 | // |
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| 30 | // |
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| 31 | // ------------------------------------------------------------ |
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| 32 | // GEANT 4 class header file |
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| 33 | // |
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| 34 | // History: first implementation, based on object model of |
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| 35 | // 30 May 1997 H.Kurashige |
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| 36 | // |
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| 37 | // Fix bug in calcuration of electron energy in DecayIt 28 Feb. 01 H.Kurashige |
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| 38 | // ------------------------------------------------------------ |
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| 39 | |
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| 40 | #include "G4ParticleDefinition.hh" |
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| 41 | #include "G4DecayProducts.hh" |
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| 42 | #include "G4VDecayChannel.hh" |
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| 43 | #include "G4TauLeptonicDecayChannel.hh" |
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| 44 | #include "Randomize.hh" |
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| 45 | #include "G4LorentzVector.hh" |
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| 46 | #include "G4LorentzRotation.hh" |
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| 47 | |
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| 48 | |
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| 49 | G4TauLeptonicDecayChannel::G4TauLeptonicDecayChannel( |
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| 50 | const G4String& theParentName, |
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| 51 | G4double theBR, |
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| 52 | const G4String& theLeptonName) |
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| 53 | :G4VDecayChannel("Tau Leptonic Decay",1) |
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| 54 | { |
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| 55 | // set names for daughter particles |
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| 56 | if (theParentName == "tau+") { |
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| 57 | SetBR(theBR); |
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| 58 | SetParent("tau+"); |
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| 59 | SetNumberOfDaughters(3); |
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| 60 | if ((theLeptonName=="e-"||theLeptonName=="e+")){ |
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| 61 | SetDaughter(0, "e+"); |
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| 62 | SetDaughter(1, "nu_e"); |
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| 63 | SetDaughter(2, "anti_nu_tau"); |
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| 64 | } else { |
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| 65 | SetDaughter(0, "mu+"); |
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| 66 | SetDaughter(1, "nu_mu"); |
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| 67 | SetDaughter(2, "anti_nu_tau"); |
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| 68 | } |
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| 69 | } else if (theParentName == "tau-") { |
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| 70 | SetBR(theBR); |
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| 71 | SetParent("tau-"); |
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| 72 | SetNumberOfDaughters(3); |
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| 73 | if ((theLeptonName=="e-"||theLeptonName=="e+")){ |
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| 74 | SetDaughter(0, "e-"); |
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| 75 | SetDaughter(1, "anti_nu_e"); |
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| 76 | SetDaughter(2, "nu_tau"); |
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| 77 | } else { |
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| 78 | SetDaughter(0, "mu-"); |
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| 79 | SetDaughter(1, "anti_nu_mu"); |
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| 80 | SetDaughter(2, "nu_tau"); |
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| 81 | } |
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| 82 | } else { |
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| 83 | #ifdef G4VERBOSE |
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| 84 | if (GetVerboseLevel()>0) { |
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| 85 | G4cout << "G4TauLeptonicDecayChannel:: constructor :"; |
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| 86 | G4cout << " parent particle is not tau but "; |
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| 87 | G4cout << theParentName << G4endl; |
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| 88 | } |
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| 89 | #endif |
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| 90 | } |
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| 91 | } |
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| 92 | |
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| 93 | G4TauLeptonicDecayChannel::~G4TauLeptonicDecayChannel() |
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| 94 | { |
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| 95 | } |
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| 96 | |
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| 97 | G4DecayProducts *G4TauLeptonicDecayChannel::DecayIt(G4double) |
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| 98 | { |
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| 99 | // this version neglects muon polarization |
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| 100 | // assumes the pure V-A coupling |
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| 101 | // gives incorrect energy spectrum for neutrinos |
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| 102 | #ifdef G4VERBOSE |
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| 103 | if (GetVerboseLevel()>1) G4cout << "G4TauLeptonicDecayChannel::DecayIt "; |
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| 104 | #endif |
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| 105 | |
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| 106 | if (parent == 0) FillParent(); |
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| 107 | if (daughters == 0) FillDaughters(); |
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| 108 | |
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| 109 | // parent mass |
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| 110 | G4double parentmass = parent->GetPDGMass(); |
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| 111 | |
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| 112 | //daughters'mass |
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| 113 | G4double daughtermass[3]; |
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| 114 | for (G4int index=0; index<3; index++){ |
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| 115 | daughtermass[index] = daughters[index]->GetPDGMass(); |
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| 116 | } |
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| 117 | |
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| 118 | //create parent G4DynamicParticle at rest |
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| 119 | G4ThreeVector dummy; |
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| 120 | G4DynamicParticle * parentparticle = new G4DynamicParticle( parent, dummy, 0.0); |
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| 121 | //create G4Decayproducts |
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| 122 | G4DecayProducts *products = new G4DecayProducts(*parentparticle); |
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| 123 | delete parentparticle; |
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| 124 | |
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| 125 | // calculate daughter momentum |
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| 126 | G4double daughtermomentum[3]; |
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| 127 | G4double energy; |
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| 128 | |
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| 129 | // calcurate lepton momentum |
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| 130 | G4double pmax = (parentmass*parentmass-daughtermass[0]*daughtermass[0])/2./parentmass; |
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| 131 | G4double p, e; |
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| 132 | G4double r; |
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| 133 | do { |
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| 134 | // determine momentum/energy |
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| 135 | r = G4UniformRand(); |
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| 136 | p = pmax*G4UniformRand(); |
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| 137 | e = std::sqrt(p*p + daughtermass[0]*daughtermass[0]); |
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| 138 | } while (r > spectrum(p,e,parentmass,daughtermass[0]) ); |
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| 139 | energy = e- daughtermass[0]; |
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| 140 | |
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| 141 | //create daughter G4DynamicParticle |
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| 142 | // daughter 0 (lepton) |
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| 143 | daughtermomentum[0] = p; |
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| 144 | G4double costheta, sintheta, phi, sinphi, cosphi; |
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| 145 | costheta = 2.*G4UniformRand()-1.0; |
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| 146 | sintheta = std::sqrt((1.0-costheta)*(1.0+costheta)); |
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| 147 | phi = twopi*G4UniformRand()*rad; |
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| 148 | sinphi = std::sin(phi); |
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| 149 | cosphi = std::cos(phi); |
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| 150 | G4ThreeVector direction0(sintheta*cosphi,sintheta*sinphi,costheta); |
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| 151 | G4DynamicParticle * daughterparticle |
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| 152 | = new G4DynamicParticle( daughters[0], direction0*daughtermomentum[0]); |
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| 153 | products->PushProducts(daughterparticle); |
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| 154 | |
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| 155 | // daughter 1 ,2 (nutrinos) |
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| 156 | // create neutrinos in the C.M frame of two neutrinos |
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| 157 | G4double energy2 = parentmass-e; |
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| 158 | G4double vmass = std::sqrt((energy2-daughtermomentum[0])*(energy2+daughtermomentum[0])); |
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| 159 | G4double beta = -1.0*daughtermomentum[0]/energy2; |
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| 160 | G4double costhetan = 2.*G4UniformRand()-1.0; |
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| 161 | G4double sinthetan = std::sqrt((1.0-costhetan)*(1.0+costhetan)); |
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| 162 | G4double phin = twopi*G4UniformRand()*rad; |
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| 163 | G4double sinphin = std::sin(phin); |
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| 164 | G4double cosphin = std::cos(phin); |
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| 165 | |
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| 166 | G4ThreeVector direction1(sinthetan*cosphin,sinthetan*sinphin,costhetan); |
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| 167 | G4DynamicParticle * daughterparticle1 |
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| 168 | = new G4DynamicParticle( daughters[1], direction1*(vmass/2.)); |
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| 169 | G4DynamicParticle * daughterparticle2 |
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| 170 | = new G4DynamicParticle( daughters[2], direction1*(-1.0*vmass/2.)); |
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| 171 | |
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| 172 | // boost to the muon rest frame |
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| 173 | G4LorentzVector p4; |
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| 174 | p4 = daughterparticle1->Get4Momentum(); |
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| 175 | p4.boost( direction0.x()*beta, direction0.y()*beta, direction0.z()*beta); |
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| 176 | daughterparticle1->Set4Momentum(p4); |
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| 177 | p4 = daughterparticle2->Get4Momentum(); |
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| 178 | p4.boost( direction0.x()*beta, direction0.y()*beta, direction0.z()*beta); |
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| 179 | daughterparticle2->Set4Momentum(p4); |
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| 180 | products->PushProducts(daughterparticle1); |
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| 181 | products->PushProducts(daughterparticle2); |
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| 182 | daughtermomentum[1] = daughterparticle1->GetTotalMomentum(); |
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| 183 | daughtermomentum[2] = daughterparticle2->GetTotalMomentum(); |
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| 184 | |
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| 185 | |
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| 186 | // output message |
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| 187 | #ifdef G4VERBOSE |
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| 188 | if (GetVerboseLevel()>1) { |
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| 189 | G4cout << "G4TauLeptonicDecayChannel::DecayIt "; |
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| 190 | G4cout << " create decay products in rest frame " <<G4endl; |
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| 191 | products->DumpInfo(); |
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| 192 | } |
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| 193 | #endif |
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| 194 | return products; |
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| 195 | } |
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| 196 | |
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| 197 | |
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| 198 | |
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| 199 | |
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| 200 | G4double G4TauLeptonicDecayChannel::spectrum(G4double p, |
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| 201 | G4double e, |
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| 202 | G4double mtau, |
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| 203 | G4double ml) |
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| 204 | { |
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| 205 | G4double f1; |
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| 206 | f1 = 3.0*e*(mtau*mtau+ml*ml)-4.0*mtau*e*e-2.0*mtau*ml*ml; |
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| 207 | return p*(f1)/(mtau*mtau*mtau*mtau)/(0.6); |
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| 208 | } |
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| 209 | |
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| 210 | |
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| 211 | |
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