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: G4DalitzDecayChannel.cc,v 1.8 2006/06/29 19:24:58 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 | // ------------------------------------------------------------ |
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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 | |
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38 | #include "G4ParticleDefinition.hh" |
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39 | #include "G4DecayProducts.hh" |
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40 | #include "G4VDecayChannel.hh" |
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41 | #include "G4DalitzDecayChannel.hh" |
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42 | #include "G4PhaseSpaceDecayChannel.hh" |
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43 | #include "Randomize.hh" |
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44 | #include "G4LorentzVector.hh" |
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45 | #include "G4LorentzRotation.hh" |
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46 | |
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47 | G4DalitzDecayChannel::G4DalitzDecayChannel( |
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48 | const G4String& theParentName, |
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49 | G4double theBR, |
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50 | const G4String& theLeptonName, |
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51 | const G4String& theAntiLeptonName) |
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52 | :G4VDecayChannel("Dalitz Decay",1) |
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53 | { |
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54 | //#ifdef G4VERBOSE |
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55 | //if (GetVerboseLevel()>1) { |
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56 | // G4cout << "G4DalitzDecayChannel:: constructor "; |
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57 | // G4cout << "addr[" << this << "]" << G4endl; |
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58 | //} |
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59 | //#endif |
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60 | // set names for daughter particles |
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61 | SetParent(theParentName); |
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62 | SetBR(theBR); |
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63 | SetNumberOfDaughters(3); |
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64 | G4String gammaName = "gamma"; |
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65 | SetDaughter(idGamma, gammaName); |
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66 | SetDaughter(idLepton, theLeptonName); |
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67 | SetDaughter(idAntiLepton, theAntiLeptonName); |
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68 | // |
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69 | //#ifdef G4VERBOSE |
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70 | //if (GetVerboseLevel()>1) DumpInfo(); |
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71 | //#endif |
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72 | } |
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73 | |
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74 | G4DalitzDecayChannel::~G4DalitzDecayChannel() |
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75 | { |
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76 | } |
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77 | |
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78 | G4DecayProducts *G4DalitzDecayChannel::DecayIt(G4double) |
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79 | { |
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80 | #ifdef G4VERBOSE |
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81 | if (GetVerboseLevel()>1) G4cout << "G4DalitzDecayChannel::DecayIt "; |
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82 | #endif |
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83 | if (parent == 0) FillParent(); |
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84 | if (daughters == 0) FillDaughters(); |
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85 | |
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86 | // parent mass |
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87 | G4double parentmass = parent->GetPDGMass(); |
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88 | |
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89 | //create parent G4DynamicParticle at rest |
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90 | G4ThreeVector dummy; |
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91 | G4DynamicParticle * parentparticle = new G4DynamicParticle( parent, dummy, 0.0); |
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92 | |
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93 | //daughters'mass |
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94 | G4double leptonmass = daughters[idLepton]->GetPDGMass(); |
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95 | |
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96 | // Generate t ( = std::exp(x):mass Square of (l+ l-) system) |
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97 | G4double xmin = 2.0*std::log(2.0*leptonmass); |
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98 | G4double xmax = 2.0*std::log(parentmass); |
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99 | G4double wmax = 1.5; |
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100 | G4double x, w, ww, w1, w2, w3, t; |
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101 | do { |
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102 | x = G4UniformRand()*(xmax-xmin) + xmin; |
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103 | w = G4UniformRand()*wmax; |
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104 | t = std::exp(x); |
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105 | w1 = (1.0-4.0*leptonmass*leptonmass/t); |
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106 | if ( w1 > 0.0) { |
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107 | w2 = ( 1.0 + 2.0*leptonmass*leptonmass/t ); |
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108 | w3 = ( 1.0 - t/parentmass/parentmass ); |
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109 | w3 = w3 * w3 * w3; |
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110 | ww = w3 * w2 * std::sqrt(w1); |
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111 | } else { |
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112 | ww = 0.0; |
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113 | } |
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114 | } while (w > ww); |
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115 | |
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116 | // calculate gamma momentum |
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117 | G4double Pgamma = |
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118 | G4PhaseSpaceDecayChannel::Pmx(parentmass, 0.0, std::sqrt(t)); |
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119 | G4double costheta = 2.*G4UniformRand()-1.0; |
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120 | G4double sintheta = std::sqrt((1.0 - costheta)*(1.0 + costheta)); |
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121 | G4double phi = twopi*G4UniformRand()*rad; |
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122 | G4ThreeVector gdirection(sintheta*std::cos(phi),sintheta*std::sin(phi),costheta); |
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123 | |
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124 | //create G4DynamicParticle for gamma |
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125 | G4DynamicParticle * gammaparticle |
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126 | = new G4DynamicParticle(daughters[idGamma] , gdirection, Pgamma); |
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127 | |
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128 | // calcurate beta of (l+ l-)system |
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129 | G4double beta = Pgamma/(parentmass-Pgamma); |
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130 | |
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131 | // calculate lepton momentum in the rest frame of (l+ l-)system |
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132 | G4double Plepton = |
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133 | G4PhaseSpaceDecayChannel::Pmx(std::sqrt(t),leptonmass, leptonmass); |
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134 | G4double Elepton = std::sqrt(Plepton*Plepton + leptonmass*leptonmass ); |
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135 | costheta = 2.*G4UniformRand()-1.0; |
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136 | sintheta = std::sqrt((1.0 - costheta)*(1.0 + costheta)); |
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137 | phi = twopi*G4UniformRand()*rad; |
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138 | G4ThreeVector ldirection(sintheta*std::cos(phi),sintheta*std::sin(phi),costheta); |
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139 | //create G4DynamicParticle for leptons in the rest frame of (l+ l-)system |
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140 | G4DynamicParticle * leptonparticle |
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141 | = new G4DynamicParticle(daughters[idLepton] , |
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142 | ldirection, Elepton-leptonmass ); |
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143 | G4DynamicParticle * antileptonparticle |
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144 | = new G4DynamicParticle(daughters[idAntiLepton] , |
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145 | -1.0*ldirection, Elepton-leptonmass ); |
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146 | //boost leptons in the rest frame of the parent |
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147 | G4LorentzVector p4 = leptonparticle->Get4Momentum(); |
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148 | p4.boost( -1.0*gdirection.x()*beta, -1.0*gdirection.y()*beta, -1.0*gdirection.z()*beta); |
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149 | leptonparticle->Set4Momentum(p4); |
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150 | p4 = antileptonparticle->Get4Momentum(); |
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151 | p4.boost( -1.0*gdirection.x()*beta, -1.0*gdirection.y()*beta, -1.0*gdirection.z()*beta); |
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152 | antileptonparticle->Set4Momentum(p4); |
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153 | |
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154 | //create G4Decayproducts |
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155 | G4DecayProducts *products = new G4DecayProducts(*parentparticle); |
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156 | delete parentparticle; |
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157 | products->PushProducts(gammaparticle); |
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158 | products->PushProducts(leptonparticle); |
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159 | products->PushProducts(antileptonparticle); |
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160 | |
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161 | #ifdef G4VERBOSE |
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162 | if (GetVerboseLevel()>1) { |
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163 | G4cout << "G4DalitzDecayChannel::DecayIt "; |
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164 | G4cout << " create decay products in rest frame " <<G4endl; |
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165 | products->DumpInfo(); |
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166 | } |
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167 | #endif |
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168 | return products; |
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169 | } |
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170 | |
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171 | |
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172 | |
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173 | |
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174 | |
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