[1] | 1 | // FragmentationFlavZpT.h is a part of the PYTHIA event generator. |
---|
| 2 | // Copyright (C) 2012 Torbjorn Sjostrand. |
---|
| 3 | // PYTHIA is licenced under the GNU GPL version 2, see COPYING for details. |
---|
| 4 | // Please respect the MCnet Guidelines, see GUIDELINES for details. |
---|
| 5 | |
---|
| 6 | // This file contains helper classes for fragmentation. |
---|
| 7 | // StringFlav is used to select quark and hadron flavours. |
---|
| 8 | // StringPT is used to select transverse momenta. |
---|
| 9 | // StringZ is used to sample the fragmentation function f(z). |
---|
| 10 | |
---|
| 11 | #ifndef Pythia8_FragmentationFlavZpT_H |
---|
| 12 | #define Pythia8_FragmentationFlavZpT_H |
---|
| 13 | |
---|
| 14 | #include "Basics.h" |
---|
| 15 | #include "ParticleData.h" |
---|
| 16 | #include "PythiaStdlib.h" |
---|
| 17 | #include "Settings.h" |
---|
| 18 | |
---|
| 19 | namespace Pythia8 { |
---|
| 20 | |
---|
| 21 | //========================================================================== |
---|
| 22 | |
---|
| 23 | // The FlavContainer class is a simple container for flavour, |
---|
| 24 | // including the extra properties needed for popcorn baryon handling. |
---|
| 25 | // id = current flavour. |
---|
| 26 | // rank = current rank; 0 for endpoint flavour and then increase by 1. |
---|
| 27 | // nPop = number of popcorn mesons yet to be produced (1 or 0). |
---|
| 28 | // idPop = (absolute sign of) popcorn quark, shared between B and Bbar. |
---|
| 29 | // idVtx = (absolute sign of) vertex (= non-shared) quark in diquark. |
---|
| 30 | |
---|
| 31 | class FlavContainer { |
---|
| 32 | |
---|
| 33 | public: |
---|
| 34 | |
---|
| 35 | // Constructor. |
---|
| 36 | FlavContainer(int idIn = 0, int rankIn = 0, int nPopIn = 0, |
---|
| 37 | int idPopIn = 0, int idVtxIn = 0) : id(idIn), rank(rankIn), |
---|
| 38 | nPop(nPopIn), idPop(idPopIn), idVtx(idVtxIn) {} |
---|
| 39 | |
---|
| 40 | // Overloaded equal operator. |
---|
| 41 | FlavContainer& operator=(const FlavContainer& flav) { if (this != &flav) { |
---|
| 42 | id = flav.id; rank = flav.rank; nPop = flav.nPop; idPop = flav.idPop; |
---|
| 43 | idVtx = flav.idVtx; } return *this; } |
---|
| 44 | |
---|
| 45 | // Invert flavour. |
---|
| 46 | FlavContainer& anti() {id = -id; return *this;} |
---|
| 47 | |
---|
| 48 | // Read in a container into another, without/with id sign flip. |
---|
| 49 | FlavContainer& copy(const FlavContainer& flav) { if (this != &flav) { |
---|
| 50 | id = flav.id; rank = flav.rank; nPop = flav.nPop; idPop = flav.idPop; |
---|
| 51 | idVtx = flav.idVtx; } return *this; } |
---|
| 52 | FlavContainer& anti(const FlavContainer& flav) { if (this != &flav) { |
---|
| 53 | id = -flav.id; rank = flav.rank; nPop = flav.nPop; idPop = flav.idPop; |
---|
| 54 | idVtx = flav.idVtx; } return *this; } |
---|
| 55 | |
---|
| 56 | // Check whether is diquark. |
---|
| 57 | bool isDiquark() {int idAbs = abs(id); |
---|
| 58 | return (idAbs > 1000 && idAbs < 10000 && (idAbs/10)%10 == 0);} |
---|
| 59 | |
---|
| 60 | // Stored properties. |
---|
| 61 | int id, rank, nPop, idPop, idVtx; |
---|
| 62 | |
---|
| 63 | }; |
---|
| 64 | |
---|
| 65 | //========================================================================== |
---|
| 66 | |
---|
| 67 | // The StringFlav class is used to select quark and hadron flavours. |
---|
| 68 | |
---|
| 69 | class StringFlav { |
---|
| 70 | |
---|
| 71 | public: |
---|
| 72 | |
---|
| 73 | // Constructor. |
---|
| 74 | StringFlav() {} |
---|
| 75 | |
---|
| 76 | // Destructor. |
---|
| 77 | virtual ~StringFlav() {} |
---|
| 78 | |
---|
| 79 | // Initialize data members. |
---|
| 80 | virtual void init(Settings& settings, Rndm* rndmPtrIn); |
---|
| 81 | |
---|
| 82 | // Pick a light d, u or s quark according to fixed ratios. |
---|
| 83 | int pickLightQ() { double rndmFlav = probQandS * rndmPtr->flat(); |
---|
| 84 | if (rndmFlav < 1.) return 1; if (rndmFlav < 2.) return 2; return 3; } |
---|
| 85 | |
---|
| 86 | // Pick a new flavour (including diquarks) given an incoming one. |
---|
| 87 | virtual FlavContainer pick(FlavContainer& flavOld); |
---|
| 88 | |
---|
| 89 | // Combine two flavours (including diquarks) to produce a hadron. |
---|
| 90 | virtual int combine(FlavContainer& flav1, FlavContainer& flav2); |
---|
| 91 | |
---|
| 92 | // Assign popcorn quark inside an original (= rank 0) diquark. |
---|
| 93 | void assignPopQ(FlavContainer& flav); |
---|
| 94 | |
---|
| 95 | // Combine two quarks to produce a diquark. |
---|
| 96 | int makeDiquark(int id1, int id2, int idHad = 0); |
---|
| 97 | |
---|
| 98 | protected: |
---|
| 99 | |
---|
| 100 | // Pointer to the random number generator. |
---|
| 101 | Rndm* rndmPtr; |
---|
| 102 | |
---|
| 103 | private: |
---|
| 104 | |
---|
| 105 | // Constants: could only be changed in the code itself. |
---|
| 106 | static const int mesonMultipletCode[6]; |
---|
| 107 | static const double baryonCGOct[6], baryonCGDec[6]; |
---|
| 108 | |
---|
| 109 | // Initialization data, to be read from Settings. |
---|
| 110 | bool suppressLeadingB; |
---|
| 111 | double probQQtoQ, probStoUD, probSQtoQQ, probQQ1toQQ0, probQandQQ, |
---|
| 112 | probQandS, probQandSinQQ, probQQ1corr, probQQ1corrInv, probQQ1norm, |
---|
| 113 | mesonRate[4][6], mesonRateSum[4], mesonMix1[2][6], mesonMix2[2][6], |
---|
| 114 | etaSup, etaPrimeSup, decupletSup, baryonCGSum[6], baryonCGMax[6], |
---|
| 115 | popcornRate, popcornSpair, popcornSmeson, scbBM[3], popFrac, |
---|
| 116 | popS[3], dWT[3][7], lightLeadingBSup, heavyLeadingBSup; |
---|
| 117 | |
---|
| 118 | }; |
---|
| 119 | |
---|
| 120 | //========================================================================== |
---|
| 121 | |
---|
| 122 | // The StringZ class is used to sample the fragmentation function f(z). |
---|
| 123 | |
---|
| 124 | class StringZ { |
---|
| 125 | |
---|
| 126 | public: |
---|
| 127 | |
---|
| 128 | // Constructor. |
---|
| 129 | StringZ() {} |
---|
| 130 | |
---|
| 131 | // Destructor. |
---|
| 132 | virtual ~StringZ() {} |
---|
| 133 | |
---|
| 134 | // Initialize data members. |
---|
| 135 | virtual void init(Settings& settings, ParticleData& particleData, |
---|
| 136 | Rndm* rndmPtrIn); |
---|
| 137 | |
---|
| 138 | // Fragmentation function: top-level to determine parameters. |
---|
| 139 | virtual double zFrag( int idOld, int idNew = 0, double mT2 = 1.); |
---|
| 140 | |
---|
| 141 | // Parameters for stopping in the middle; overloaded for Hidden Valley. |
---|
| 142 | virtual double stopMass() {return stopM;} |
---|
| 143 | virtual double stopNewFlav() {return stopNF;} |
---|
| 144 | virtual double stopSmear() {return stopS;} |
---|
| 145 | |
---|
| 146 | // b fragmentation parameter needed to weight final two solutions. |
---|
| 147 | virtual double bAreaLund() {return bLund;} |
---|
| 148 | |
---|
| 149 | protected: |
---|
| 150 | |
---|
| 151 | // Constants: could only be changed in the code itself. |
---|
| 152 | static const double CFROMUNITY, AFROMZERO, AFROMC, EXPMAX; |
---|
| 153 | |
---|
| 154 | // Initialization data, to be read from Settings. |
---|
| 155 | bool usePetersonC, usePetersonB, usePetersonH; |
---|
| 156 | double mc2, mb2, aLund, bLund, aExtraDiquark, rFactC, rFactB, rFactH, |
---|
| 157 | epsilonC, epsilonB, epsilonH, stopM, stopNF, stopS; |
---|
| 158 | |
---|
| 159 | // Fragmentation function: select z according to provided parameters. |
---|
| 160 | double zLund( double a, double b, double c = 1.); |
---|
| 161 | double zPeterson( double epsilon); |
---|
| 162 | |
---|
| 163 | // Pointer to the random number generator. |
---|
| 164 | Rndm* rndmPtr; |
---|
| 165 | |
---|
| 166 | }; |
---|
| 167 | |
---|
| 168 | //========================================================================== |
---|
| 169 | |
---|
| 170 | // The StringPT class is used to select select transverse momenta. |
---|
| 171 | |
---|
| 172 | class StringPT { |
---|
| 173 | |
---|
| 174 | public: |
---|
| 175 | |
---|
| 176 | // Constructor. |
---|
| 177 | StringPT() {} |
---|
| 178 | |
---|
| 179 | // Destructor. |
---|
| 180 | virtual ~StringPT() {} |
---|
| 181 | |
---|
| 182 | // Initialize data members. |
---|
| 183 | virtual void init(Settings& settings, ParticleData& particleData, |
---|
| 184 | Rndm* rndmPtrIn); |
---|
| 185 | |
---|
| 186 | // Return px and py as a pair in the same call. |
---|
| 187 | pair<double, double> pxy(); |
---|
| 188 | |
---|
| 189 | // Gaussian suppression of given pT2; used in MiniStringFragmentation. |
---|
| 190 | double suppressPT2(double pT2) { return exp( -pT2 / sigma2Had); } |
---|
| 191 | |
---|
| 192 | protected: |
---|
| 193 | |
---|
| 194 | // Constants: could only be changed in the code itself. |
---|
| 195 | static const double SIGMAMIN; |
---|
| 196 | |
---|
| 197 | // Initialization data, to be read from Settings. |
---|
| 198 | double sigmaQ, enhancedFraction, enhancedWidth, sigma2Had; |
---|
| 199 | |
---|
| 200 | // Pointer to the random number generator. |
---|
| 201 | Rndm* rndmPtr; |
---|
| 202 | |
---|
| 203 | }; |
---|
| 204 | |
---|
| 205 | //========================================================================== |
---|
| 206 | |
---|
| 207 | } // end namespace Pythia8 |
---|
| 208 | |
---|
| 209 | #endif // Pythia8_FragmentationFlavZpT_H |
---|