[1] | 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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