1 | // StringFragmentation.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 for string fragmentation. |
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7 | // StringEnd: keeps track of the fragmentation step. |
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8 | // StringFragmentation: is the top-level class. |
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9 | |
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10 | #ifndef Pythia8_StringFragmentation_H |
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11 | #define Pythia8_StringFragmentation_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 "Info.h" |
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16 | #include "FragmentationFlavZpT.h" |
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17 | #include "FragmentationSystems.h" |
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18 | #include "ParticleData.h" |
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19 | #include "PythiaStdlib.h" |
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20 | #include "Settings.h" |
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21 | |
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22 | namespace Pythia8 { |
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23 | |
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24 | //========================================================================== |
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25 | |
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26 | // The StringEnd class contains the information related to |
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27 | // one of the current endpoints of the string system. |
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28 | // Only to be used inside StringFragmentation, so no private members. |
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29 | |
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30 | class StringEnd { |
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31 | |
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32 | public: |
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33 | |
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34 | // Constructor. |
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35 | StringEnd() {} |
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36 | |
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37 | // Save pointers. |
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38 | void init( ParticleData* particleDataPtrIn, StringFlav* flavSelPtrIn, |
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39 | StringPT* pTSelPtrIn, StringZ* zSelPtrIn) { |
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40 | particleDataPtr = particleDataPtrIn; flavSelPtr = flavSelPtrIn; |
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41 | pTSelPtr = pTSelPtrIn; zSelPtr = zSelPtrIn;} |
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42 | |
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43 | // Set up initial endpoint values from input. |
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44 | void setUp(bool fromPosIn, int iEndIn, int idOldIn, int iMaxIn, |
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45 | double pxIn, double pyIn, double GammaIn, double xPosIn, double xNegIn); |
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46 | |
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47 | // Fragment off one hadron from the string system, in flavour and pT. |
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48 | void newHadron(); |
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49 | |
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50 | // Fragment off one hadron from the string system, in momentum space, |
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51 | // by taking steps either from positive or from negative end. |
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52 | Vec4 kinematicsHadron(StringSystem& system); |
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53 | |
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54 | // Update string end information after a hadron has been removed. |
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55 | void update(); |
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56 | |
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57 | // Constants: could only be changed in the code itself. |
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58 | static const double TINY, PT2SAME; |
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59 | |
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60 | // Pointer to the particle data table. |
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61 | ParticleData* particleDataPtr; |
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62 | |
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63 | // Pointers to classes for flavour, pT and z generation. |
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64 | StringFlav* flavSelPtr; |
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65 | StringPT* pTSelPtr; |
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66 | StringZ* zSelPtr; |
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67 | |
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68 | // Data members. |
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69 | bool fromPos; |
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70 | int iEnd, iMax, idHad, iPosOld, iNegOld, iPosNew, iNegNew; |
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71 | double pxOld, pyOld, pxNew, pyNew, pxHad, pyHad, mHad, mT2Had, zHad, |
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72 | GammaOld, GammaNew, xPosOld, xPosNew, xPosHad, xNegOld, xNegNew, |
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73 | xNegHad; |
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74 | FlavContainer flavOld, flavNew; |
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75 | Vec4 pHad, pSoFar; |
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76 | |
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77 | }; |
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78 | |
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79 | //========================================================================== |
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80 | |
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81 | // The StringFragmentation class contains the top-level routines |
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82 | // to fragment a colour singlet partonic system. |
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83 | |
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84 | class StringFragmentation { |
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85 | |
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86 | public: |
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87 | |
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88 | // Constructor. |
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89 | StringFragmentation() {} |
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90 | |
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91 | // Initialize and save pointers. |
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92 | void init(Info* infoPtrIn, Settings& settings, |
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93 | ParticleData* particleDataPtrIn, Rndm* rndmPtrIn, |
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94 | StringFlav* flavSelPtrIn, StringPT* pTSelPtrIn, StringZ* zSelPtrIn); |
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95 | |
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96 | // Do the fragmentation: driver routine. |
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97 | bool fragment( int iSub, ColConfig& colConfig, Event& event); |
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98 | |
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99 | // Find the boost matrix to the rest frame of a junction. |
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100 | RotBstMatrix junctionRestFrame(Vec4& p0, Vec4& p1, Vec4& p2); |
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101 | |
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102 | private: |
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103 | |
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104 | // Constants: could only be changed in the code itself. |
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105 | static const int NTRYFLAV, NTRYJOIN, NSTOPMASS, NTRYJNREST, |
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106 | NTRYJNMATCH, NTRYJRFEQ; |
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107 | static const double FACSTOPMASS, CLOSEDM2MAX, CLOSEDM2FRAC, EXPMAX, |
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108 | MATCHPOSNEG, EJNWEIGHTMAX, CONVJNREST, M2MAXJRF, |
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109 | EEXTRAJNMATCH, MDIQUARKMIN, CONVJRFEQ; |
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110 | |
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111 | // Pointer to various information on the generation. |
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112 | Info* infoPtr; |
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113 | |
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114 | // Pointer to the particle data table. |
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115 | ParticleData* particleDataPtr; |
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116 | |
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117 | // Pointer to the random number generator. |
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118 | Rndm* rndmPtr; |
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119 | |
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120 | // Pointers to classes for flavour, pT and z generation. |
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121 | StringFlav* flavSelPtr; |
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122 | StringPT* pTSelPtr; |
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123 | StringZ* zSelPtr; |
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124 | |
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125 | // Initialization data, read from Settings. |
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126 | double stopMass, stopNewFlav, stopSmear, eNormJunction, |
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127 | eBothLeftJunction, eMaxLeftJunction, eMinLeftJunction, |
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128 | mJoin, bLund; |
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129 | |
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130 | // Data members. |
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131 | bool hasJunction, isClosed; |
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132 | int iPos, iNeg; |
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133 | double w2Rem, stopMassNow; |
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134 | Vec4 pSum, pRem, pJunctionHadrons; |
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135 | |
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136 | // List of partons in string system. |
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137 | vector<int> iParton; |
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138 | |
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139 | // Temporary event record for the produced particles. |
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140 | Event hadrons; |
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141 | |
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142 | // Information on the system of string regions. |
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143 | StringSystem system, systemMin, systemMid; |
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144 | |
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145 | // Information on the two current endpoints of the fragmenting system. |
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146 | StringEnd posEnd, negEnd; |
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147 | |
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148 | // Find region where to put first string break for closed gluon loop. |
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149 | vector<int> findFirstRegion(vector<int>& iPartonIn, Event& event); |
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150 | |
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151 | // Set flavours and momentum position for initial string endpoints. |
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152 | void setStartEnds(int idPos, int idNeg, StringSystem systemNow); |
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153 | |
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154 | // Check remaining energy-momentum whether it is OK to continue. |
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155 | bool energyUsedUp(bool fromPos); |
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156 | |
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157 | // Produce the final two partons to complete the system. |
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158 | bool finalTwo(bool fromPos); |
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159 | |
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160 | // Construct a special joining region for the final two hadrons. |
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161 | StringRegion finalRegion(); |
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162 | |
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163 | // Store the hadrons in the normal event record, ordered from one end. |
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164 | void store(Event& event); |
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165 | |
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166 | // Fragment off two of the string legs in to a junction. |
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167 | bool fragmentToJunction(Event& event); |
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168 | |
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169 | // Join extra nearby partons when stuck. |
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170 | int extraJoin(double facExtra, Event& event); |
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171 | |
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172 | }; |
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173 | |
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174 | //========================================================================== |
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175 | |
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176 | } // end namespace Pythia8 |
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177 | |
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178 | #endif // Pythia8_StringFragmentation_H |
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