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 |
---|