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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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15 | // * use. Please see the license in the file LICENSE and URL above * |
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24 | // ******************************************************************** |
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25 | // |
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26 | // |
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27 | // |
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28 | // ------------------------------------------------------------ |
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29 | // GEANT 4 class header file |
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30 | // |
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31 | // ---------------- G4SampleResonance ---------------- |
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32 | // by Henning Weber, March 2001. |
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33 | // helper class for sampling resonance masses |
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34 | // ------------------------------------------------------------ |
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35 | |
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36 | |
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37 | #include "globals.hh" |
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38 | #include <iostream> |
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39 | #include "G4SampleResonance.hh" |
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40 | #include "G4DecayTable.hh" |
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41 | #include "Randomize.hh" |
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42 | #include "G4HadronicException.hh" |
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43 | |
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44 | G4SampleResonance::minMassMapType G4SampleResonance::minMassCache; |
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45 | |
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46 | G4double G4SampleResonance::GetMinimumMass(const G4ParticleDefinition* p) const |
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47 | { |
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48 | |
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49 | G4double minResonanceMass = DBL_MAX; |
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50 | |
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51 | if ( p->IsShortLived() ) |
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52 | { |
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53 | minMassMapIterator i = minMassCache.find(p); |
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54 | if ( i!=minMassCache.end() ) |
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55 | { |
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56 | minResonanceMass = (*i).second; |
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57 | } |
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58 | else |
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59 | { |
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60 | // G4cout << "--> request for " << p->GetParticleName() << G4endl; |
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61 | |
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62 | const G4DecayTable* theDecays = const_cast<G4ParticleDefinition*>(p)->GetDecayTable(); |
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63 | const G4int nDecays = theDecays->entries(); |
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64 | |
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65 | for (G4int i=0; i<nDecays; i++) |
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66 | { |
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67 | const G4VDecayChannel* aDecay = theDecays->GetDecayChannel(i); |
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68 | const G4int nDaughters = aDecay->GetNumberOfDaughters(); |
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69 | |
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70 | G4double minChannelMass = 0; |
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71 | |
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72 | for (G4int j=0; j<nDaughters; j++) |
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73 | { |
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74 | const G4ParticleDefinition* aDaughter = const_cast<G4VDecayChannel*>(aDecay)->GetDaughter(j); |
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75 | G4double minMass = GetMinimumMass(aDaughter); |
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76 | if (!minMass) minMass = DBL_MAX; // exclude gamma channel; |
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77 | minChannelMass+=minMass; |
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78 | } |
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79 | // G4cout << "channel mass for the above is " << minChannelMass/MeV << G4endl; |
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80 | if (minChannelMass < minResonanceMass) minResonanceMass = minChannelMass; |
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81 | |
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82 | } |
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83 | // replace this as soon as the compiler supports mutable!! |
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84 | G4SampleResonance* self = const_cast<G4SampleResonance*>(this); |
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85 | (self->minMassCache)[p] = minResonanceMass; |
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86 | |
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87 | } |
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88 | } |
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89 | else |
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90 | { |
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91 | |
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92 | minResonanceMass = p->GetPDGMass(); |
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93 | |
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94 | } |
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95 | // G4cout << "minimal mass for " << p->GetParticleName() << " is " << minResonanceMass/MeV << G4endl; |
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96 | |
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97 | return minResonanceMass; |
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98 | } |
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99 | |
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100 | |
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101 | |
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102 | G4double G4SampleResonance::SampleMass(const G4ParticleDefinition* p, const G4double maxMass) const |
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103 | { |
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104 | return SampleMass(p->GetPDGMass(), p->GetPDGWidth(), GetMinimumMass(p), maxMass); |
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105 | } |
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106 | |
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107 | |
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108 | G4double G4SampleResonance::SampleMass(const G4double poleMass, |
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109 | const G4double gamma, |
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110 | const G4double minMass, |
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111 | const G4double maxMass) const |
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112 | { |
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113 | // Chooses a mass randomly between minMass and maxMass |
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114 | // according to a Breit-Wigner function with constant |
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115 | // width gamma and pole poleMass |
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116 | |
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117 | if ( minMass > maxMass ) |
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118 | { |
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119 | throw G4HadronicException(__FILE__, __LINE__, |
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120 | "SampleResonanceMass: mass range negative (minMass>maxMass)"); |
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121 | } |
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122 | |
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123 | G4double returnMass; |
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124 | |
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125 | if ( gamma < DBL_EPSILON ) |
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126 | { |
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127 | returnMass = std::max(minMass, std::min(maxMass, poleMass)); |
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128 | } |
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129 | else |
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130 | { |
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131 | double fmin = BrWigInt0(minMass, gamma, poleMass); |
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132 | double fmax = BrWigInt0(maxMass, gamma, poleMass); |
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133 | double f = fmin + (fmax-fmin)*G4UniformRand(); |
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134 | returnMass = BrWigInv(f, gamma, poleMass); |
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135 | } |
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136 | |
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137 | return returnMass; |
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138 | } |
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139 | |
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140 | |
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141 | |
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142 | |
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