Line data Source code
1 : // StringFragmentation.h is a part of the PYTHIA event generator.
2 : // Copyright (C) 2015 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 the classes for string fragmentation.
7 : // StringEnd: keeps track of the fragmentation step.
8 : // StringFragmentation: is the top-level class.
9 :
10 : #ifndef Pythia8_StringFragmentation_H
11 : #define Pythia8_StringFragmentation_H
12 :
13 : #include "Pythia8/Basics.h"
14 : #include "Pythia8/Event.h"
15 : #include "Pythia8/Info.h"
16 : #include "Pythia8/FragmentationFlavZpT.h"
17 : #include "Pythia8/FragmentationSystems.h"
18 : #include "Pythia8/ParticleData.h"
19 : #include "Pythia8/PythiaStdlib.h"
20 : #include "Pythia8/Settings.h"
21 :
22 : namespace Pythia8 {
23 :
24 : //==========================================================================
25 :
26 : // The StringEnd class contains the information related to
27 : // one of the current endpoints of the string system.
28 : // Only to be used inside StringFragmentation, so no private members.
29 :
30 : class StringEnd {
31 :
32 : public:
33 :
34 : // Constructor.
35 0 : StringEnd() {}
36 :
37 : // Save pointers.
38 : void init( ParticleData* particleDataPtrIn, StringFlav* flavSelPtrIn,
39 : StringPT* pTSelPtrIn, StringZ* zSelPtrIn) {
40 0 : particleDataPtr = particleDataPtrIn; flavSelPtr = flavSelPtrIn;
41 0 : pTSelPtr = pTSelPtrIn; zSelPtr = zSelPtrIn;}
42 :
43 : // Set up initial endpoint values from input.
44 : void setUp(bool fromPosIn, int iEndIn, int idOldIn, int iMaxIn,
45 : double pxIn, double pyIn, double GammaIn, double xPosIn, double xNegIn);
46 :
47 : // Fragment off one hadron from the string system, in flavour and pT.
48 : void newHadron();
49 :
50 : // Fragment off one hadron from the string system, in momentum space,
51 : // by taking steps either from positive or from negative end.
52 : Vec4 kinematicsHadron(StringSystem& system);
53 :
54 : // Update string end information after a hadron has been removed.
55 : void update();
56 :
57 : // Constants: could only be changed in the code itself.
58 : static const double TINY, PT2SAME;
59 :
60 : // Pointer to the particle data table.
61 : ParticleData* particleDataPtr;
62 :
63 : // Pointers to classes for flavour, pT and z generation.
64 : StringFlav* flavSelPtr;
65 : StringPT* pTSelPtr;
66 : StringZ* zSelPtr;
67 :
68 : // Data members.
69 : bool fromPos;
70 : int iEnd, iMax, idHad, iPosOld, iNegOld, iPosNew, iNegNew;
71 : double pxOld, pyOld, pxNew, pyNew, pxHad, pyHad, mHad, mT2Had, zHad,
72 : GammaOld, GammaNew, xPosOld, xPosNew, xPosHad, xNegOld, xNegNew,
73 : xNegHad;
74 : FlavContainer flavOld, flavNew;
75 : Vec4 pHad, pSoFar;
76 :
77 : };
78 :
79 : //==========================================================================
80 :
81 : // The StringFragmentation class contains the top-level routines
82 : // to fragment a colour singlet partonic system.
83 :
84 0 : class StringFragmentation {
85 :
86 : public:
87 :
88 : // Constructor.
89 0 : StringFragmentation() {}
90 :
91 : // Initialize and save pointers.
92 : void init(Info* infoPtrIn, Settings& settings,
93 : ParticleData* particleDataPtrIn, Rndm* rndmPtrIn,
94 : StringFlav* flavSelPtrIn, StringPT* pTSelPtrIn, StringZ* zSelPtrIn);
95 :
96 : // Do the fragmentation: driver routine.
97 : bool fragment( int iSub, ColConfig& colConfig, Event& event);
98 :
99 : // Find the boost matrix to the rest frame of a junction.
100 : RotBstMatrix junctionRestFrame(Vec4& p0, Vec4& p1, Vec4& p2);
101 :
102 : private:
103 :
104 : // Constants: could only be changed in the code itself.
105 : static const int NTRYFLAV, NTRYJOIN, NSTOPMASS, NTRYJNREST,
106 : NTRYJNMATCH, NTRYJRFEQ;
107 : static const double FACSTOPMASS, CLOSEDM2MAX, CLOSEDM2FRAC, EXPMAX,
108 : MATCHPOSNEG, EJNWEIGHTMAX, CONVJNREST, M2MAXJRF,
109 : EEXTRAJNMATCH, MDIQUARKMIN, CONVJRFEQ, M2MINJRF;
110 :
111 : // Pointer to various information on the generation.
112 : Info* infoPtr;
113 :
114 : // Pointer to the particle data table.
115 : ParticleData* particleDataPtr;
116 :
117 : // Pointer to the random number generator.
118 : Rndm* rndmPtr;
119 :
120 : // Pointers to classes for flavour, pT and z generation.
121 : StringFlav* flavSelPtr;
122 : StringPT* pTSelPtr;
123 : StringZ* zSelPtr;
124 :
125 : // Initialization data, read from Settings.
126 : double stopMass, stopNewFlav, stopSmear, eNormJunction,
127 : eBothLeftJunction, eMaxLeftJunction, eMinLeftJunction,
128 : mJoin, bLund;
129 :
130 : // Data members.
131 : bool hasJunction, isClosed;
132 : int iPos, iNeg;
133 : double w2Rem, stopMassNow;
134 : Vec4 pSum, pRem, pJunctionHadrons;
135 :
136 : // List of partons in string system.
137 : vector<int> iParton;
138 :
139 : // Temporary event record for the produced particles.
140 : Event hadrons;
141 :
142 : // Information on the system of string regions.
143 : StringSystem system, systemMin, systemMid;
144 :
145 : // Information on the two current endpoints of the fragmenting system.
146 : StringEnd posEnd, negEnd;
147 :
148 : // Find region where to put first string break for closed gluon loop.
149 : vector<int> findFirstRegion(vector<int>& iPartonIn, Event& event);
150 :
151 : // Set flavours and momentum position for initial string endpoints.
152 : void setStartEnds(int idPos, int idNeg, StringSystem systemNow);
153 :
154 : // Check remaining energy-momentum whether it is OK to continue.
155 : bool energyUsedUp(bool fromPos);
156 :
157 : // Produce the final two partons to complete the system.
158 : bool finalTwo(bool fromPos, Event& event, bool usedPosJun, bool usedNegJun);
159 :
160 : // Construct a special joining region for the final two hadrons.
161 : StringRegion finalRegion();
162 :
163 : // Store the hadrons in the normal event record, ordered from one end.
164 : void store(Event& event);
165 :
166 : // Fragment off two of the string legs in to a junction.
167 : bool fragmentToJunction(Event& event);
168 :
169 : // Join extra nearby partons when stuck.
170 : int extraJoin(double facExtra, Event& event);
171 :
172 : };
173 :
174 : //==========================================================================
175 :
176 : } // end namespace Pythia8
177 :
178 : #endif // Pythia8_StringFragmentation_H
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