1 | // ParticleDecays.h is a part of the PYTHIA event generator. |
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2 | // Copyright (C) 2012 Torbjorn Sjostrand. |
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3 | // PYTHIA is licenced under the GNU GPL version 2, see COPYING for details. |
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4 | // Please respect the MCnet Guidelines, see GUIDELINES for details. |
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5 | |
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6 | // This file contains the classes to perform a particle decay. |
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7 | // DecayHandler: base class for external handling of decays. |
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8 | // ParticleDecays: decay a particle. |
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9 | |
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10 | #ifndef Pythia8_ParticleDecays_H |
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11 | #define Pythia8_ParticleDecays_H |
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12 | |
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13 | #include "Basics.h" |
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14 | #include "Event.h" |
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15 | #include "FragmentationFlavZpT.h" |
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16 | #include "Info.h" |
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17 | #include "ParticleData.h" |
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18 | #include "PythiaStdlib.h" |
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19 | #include "Settings.h" |
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20 | #include "TimeShower.h" |
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21 | #include "TauDecays.h" |
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22 | |
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23 | namespace Pythia8 { |
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24 | |
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25 | //========================================================================== |
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26 | |
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27 | // DecayHandler is base class for the external handling of decays. |
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28 | // There is only one pure virtual method, that should do the decay. |
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29 | |
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30 | class DecayHandler { |
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31 | |
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32 | public: |
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33 | |
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34 | // A pure virtual method, wherein the derived class method does a decay. |
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35 | virtual bool decay(vector<int>& idProd, vector<double>& mProd, |
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36 | vector<Vec4>& pProd, int iDec, const Event& event) = 0; |
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37 | |
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38 | protected: |
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39 | |
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40 | // Destructor. |
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41 | virtual ~DecayHandler() {} |
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42 | |
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43 | }; |
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44 | |
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45 | //========================================================================== |
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46 | |
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47 | // The ParticleDecays class contains the routines to decay a particle. |
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48 | |
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49 | class ParticleDecays { |
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50 | |
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51 | public: |
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52 | |
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53 | // Constructor. |
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54 | ParticleDecays() {} |
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55 | |
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56 | // Initialize: store pointers and find settings |
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57 | void init(Info* infoPtrIn, Settings& settings, |
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58 | ParticleData* particleDataPtrIn, Rndm* rndmPtrIn, |
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59 | Couplings* couplingsPtrIn, TimeShower* timesDecPtrIn, |
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60 | StringFlav* flavSelPtrIn, DecayHandler* decayHandlePtrIn, |
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61 | vector<int> handledParticles); |
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62 | |
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63 | // Perform a decay of a single particle. |
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64 | bool decay(int iDec, Event& event); |
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65 | |
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66 | // Did decay result in new partons to hadronize? |
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67 | bool moreToDo() const {return hasPartons && keepPartons;} |
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68 | |
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69 | private: |
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70 | |
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71 | // Constants: could only be changed in the code itself. |
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72 | static const int NTRYDECAY, NTRYPICK, NTRYMEWT, NTRYDALITZ; |
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73 | static const double MSAFEDALITZ, WTCORRECTION[11]; |
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74 | |
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75 | // Pointer to various information on the generation. |
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76 | Info* infoPtr; |
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77 | |
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78 | // Pointer to the particle data table. |
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79 | ParticleData* particleDataPtr; |
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80 | |
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81 | // Pointer to the random number generator. |
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82 | Rndm* rndmPtr; |
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83 | |
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84 | // Pointers to Standard Model couplings. |
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85 | Couplings* couplingsPtr; |
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86 | |
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87 | // Pointers to timelike showers, for decays to partons (e.g. Upsilon). |
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88 | TimeShower* timesDecPtr; |
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89 | |
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90 | // Pointer to class for flavour generation; needed when to pick hadrons. |
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91 | StringFlav* flavSelPtr; |
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92 | |
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93 | // Pointer to a handler of external decays. |
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94 | DecayHandler* decayHandlePtr; |
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95 | |
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96 | // Initialization data, read from Settings. |
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97 | bool limitTau0, limitTau, limitRadius, limitCylinder, limitDecay, |
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98 | mixB, doFSRinDecays; |
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99 | int sophisticatedTau; |
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100 | double mSafety, tau0Max, tauMax, rMax, xyMax, zMax, xBdMix, xBsMix, |
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101 | sigmaSoft, multIncrease, multIncreaseWeak, multRefMass, multGoffset, |
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102 | colRearrange, stopMass, sRhoDal, wRhoDal; |
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103 | |
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104 | // Multiplicity. Decay products positions and masses. |
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105 | bool hasPartons, keepPartons; |
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106 | int idDec, meMode, mult; |
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107 | double scale; |
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108 | vector<int> iProd, idProd, cols, acols, idPartons; |
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109 | vector<double> mProd, mInv, rndmOrd; |
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110 | vector<Vec4> pInv, pProd; |
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111 | vector<FlavContainer> flavEnds; |
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112 | |
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113 | // Pointer to particle data for currently decaying particle |
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114 | ParticleDataEntry* decDataPtr; |
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115 | |
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116 | // Tau particle decayer. |
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117 | TauDecays tauDecayer; |
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118 | |
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119 | // Check whether a decay is allowed, given the upcoming decay vertex. |
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120 | bool checkVertex(Particle& decayer); |
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121 | |
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122 | // Check for oscillations B0 <-> B0bar or B_s0 <-> B_s0bar. |
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123 | bool oscillateB(Particle& decayer); |
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124 | |
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125 | // Do a one-body decay. |
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126 | bool oneBody(Event& event); |
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127 | |
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128 | // Do a two-body decay; |
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129 | bool twoBody(Event& event); |
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130 | |
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131 | // Do a three-body decay; |
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132 | bool threeBody(Event& event); |
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133 | |
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134 | // Do a multibody decay using the M-generator algorithm. |
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135 | bool mGenerator(Event& event); |
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136 | |
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137 | // Select mass of lepton pair in a Dalitz decay. |
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138 | bool dalitzMass(); |
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139 | |
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140 | // Do kinematics of gamma* -> l- l+ in Dalitz decay. |
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141 | bool dalitzKinematics(Event& event); |
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142 | |
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143 | // Translate a partonic content into a set of actual hadrons. |
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144 | bool pickHadrons(); |
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145 | |
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146 | // Set colour flow and scale in a decay explicitly to partons. |
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147 | bool setColours(Event& event); |
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148 | |
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149 | }; |
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150 | |
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151 | //========================================================================== |
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152 | |
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153 | } // end namespace Pythia8 |
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154 | |
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155 | #endif // Pythia8_ParticleDecays_H |
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