[1] | 1 | // main82.cc 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 program is written by Stefan Prestel. |
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| 7 | // It illustrates how to do CKKW-L merging, |
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| 8 | // see the Matrix Element Merging page in the online manual. |
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| 9 | |
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| 10 | #include "Pythia.h" |
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| 11 | |
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| 12 | using namespace Pythia8; |
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| 13 | |
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| 14 | // Functions for histogramming |
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| 15 | #include "fastjet/PseudoJet.hh" |
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| 16 | #include "fastjet/ClusterSequence.hh" |
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| 17 | #include "fastjet/CDFMidPointPlugin.hh" |
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| 18 | #include "fastjet/CDFJetCluPlugin.hh" |
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| 19 | #include "fastjet/D0RunIIConePlugin.hh" |
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| 20 | |
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| 21 | //========================================================================== |
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| 22 | |
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| 23 | // Find the Durham kT separation of the clustering from |
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| 24 | // nJetMin --> nJetMin-1 jets in te input event |
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| 25 | |
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| 26 | double pTfirstJet( const Event& event, int nJetMin, double Rparam) { |
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| 27 | |
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| 28 | double yPartonMax = 4.; |
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| 29 | |
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| 30 | // Fastjet analysis - select algorithm and parameters |
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| 31 | fastjet::Strategy strategy = fastjet::Best; |
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| 32 | fastjet::RecombinationScheme recombScheme = fastjet::E_scheme; |
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| 33 | fastjet::JetDefinition *jetDef = NULL; |
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| 34 | // For hadronic collision, use hadronic Durham kT measure |
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| 35 | if(event[3].colType() != 0 || event[4].colType() != 0) |
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| 36 | jetDef = new fastjet::JetDefinition(fastjet::kt_algorithm, Rparam, |
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| 37 | recombScheme, strategy); |
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| 38 | // For e+e- collision, use e+e- Durham kT measure |
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| 39 | else |
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| 40 | jetDef = new fastjet::JetDefinition(fastjet::ee_kt_algorithm, |
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| 41 | recombScheme, strategy); |
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| 42 | // Fastjet input |
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| 43 | std::vector <fastjet::PseudoJet> fjInputs; |
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| 44 | // Reset Fastjet input |
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| 45 | fjInputs.resize(0); |
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| 46 | |
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| 47 | // Loop over event record to decide what to pass to FastJet |
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| 48 | for (int i = 0; i < event.size(); ++i) { |
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| 49 | // (Final state && coloured+photons) only! |
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| 50 | if ( !event[i].isFinal() |
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| 51 | || event[i].isLepton() |
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| 52 | || event[i].id() == 23 |
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| 53 | || abs(event[i].id()) == 24 |
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| 54 | || abs(event[i].y()) > yPartonMax) |
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| 55 | continue; |
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| 56 | |
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| 57 | // Store as input to Fastjet |
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| 58 | fjInputs.push_back( fastjet::PseudoJet (event[i].px(), |
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| 59 | event[i].py(), event[i].pz(),event[i].e() ) ); |
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| 60 | } |
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| 61 | |
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| 62 | // Do nothing for empty input |
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| 63 | if (int(fjInputs.size()) == 0) { |
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| 64 | delete jetDef; |
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| 65 | return 0.0; |
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| 66 | } |
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| 67 | |
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| 68 | // Run Fastjet algorithm |
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| 69 | fastjet::ClusterSequence clustSeq(fjInputs, *jetDef); |
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| 70 | // Extract kT of first clustering |
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| 71 | double pTFirst = sqrt(clustSeq.exclusive_dmerge_max(nJetMin-1)); |
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| 72 | |
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| 73 | delete jetDef; |
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| 74 | // Return kT |
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| 75 | return pTFirst; |
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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 | // Class for user interaction with the merging |
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| 82 | |
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| 83 | class MyMergingHooks : public MergingHooks { |
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| 84 | |
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| 85 | private: |
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| 86 | |
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| 87 | public: |
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| 88 | |
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| 89 | // Default constructor |
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| 90 | MyMergingHooks(); |
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| 91 | // Destructor |
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| 92 | ~MyMergingHooks(); |
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| 93 | |
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| 94 | // Functional definition of the merging scale |
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| 95 | virtual double tmsDefinition( const Event& event); |
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| 96 | |
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| 97 | // Helper function for tms definition |
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| 98 | double myKTdurham(const Particle& RadAfterBranch, |
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| 99 | const Particle& EmtAfterBranch, int Type, double D ); |
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| 100 | |
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| 101 | }; |
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| 102 | |
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| 103 | //-------------------------------------------------------------------------- |
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| 104 | |
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| 105 | // Constructor |
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| 106 | MyMergingHooks::MyMergingHooks() {} |
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| 107 | |
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| 108 | // Destructor |
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| 109 | MyMergingHooks::~MyMergingHooks() {} |
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| 110 | |
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| 111 | //-------------------------------------------------------------------------- |
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| 112 | |
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| 113 | // Definition of the merging scale |
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| 114 | |
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| 115 | double MyMergingHooks::tmsDefinition( const Event& event){ |
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| 116 | |
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| 117 | // Cut only on QCD partons! |
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| 118 | // Count particle types |
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| 119 | int nFinalColoured = 0; |
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| 120 | int nFinalNow =0; |
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| 121 | for( int i=0; i < event.size(); ++i) { |
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| 122 | if(event[i].isFinal()){ |
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| 123 | if(event[i].id() != 23 && abs(event[i].id()) != 24) |
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| 124 | nFinalNow++; |
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| 125 | if( event[i].colType() != 0) |
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| 126 | nFinalColoured++; |
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| 127 | } |
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| 128 | } |
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| 129 | |
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| 130 | // Use MergingHooks in-built functions to get information on the hard process |
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| 131 | int nLeptons = nHardOutLeptons(); |
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| 132 | int nQuarks = nHardOutPartons(); |
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| 133 | int nResNow = nResInCurrent(); |
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| 134 | |
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| 135 | // Check if photons, electrons etc. have been produced. If so, do not veto |
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| 136 | if(nFinalNow - ( (nLeptons+nQuarks)/2 - nResNow)*2 != nFinalColoured){ |
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| 137 | // Sometimes, Pythia detaches the decay products even though no |
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| 138 | // resonance was put into the LHE file, to catch this, add another |
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| 139 | // if statement |
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| 140 | if(nFinalNow != nFinalColoured) return 0.; |
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| 141 | } |
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| 142 | |
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| 143 | // Check that one parton has been produced. If not (e.g. in MPI), do not veto |
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| 144 | int nMPI = infoPtr->nMPI(); |
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| 145 | if(nMPI > 1) return 0.; |
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| 146 | |
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| 147 | // Declare kT algorithm parameters |
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| 148 | double Dparam = 0.4; |
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| 149 | int kTtype = -1; |
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| 150 | // Declare final parton vector |
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| 151 | vector <int> FinalPartPos; |
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| 152 | FinalPartPos.clear(); |
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| 153 | // Search event record for final state partons |
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| 154 | for (int i=0; i < event.size(); ++i) |
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| 155 | if(event[i].isFinal() && event[i].colType() != 0) |
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| 156 | FinalPartPos.push_back(i); |
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| 157 | |
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| 158 | // Find minimal Durham kT in event, using own function: Check |
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| 159 | // definition of separation |
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| 160 | int type = (event[3].colType() == 0 && event[4].colType() == 0) ? 1 : kTtype; |
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| 161 | // Find minimal kT |
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| 162 | double ktmin = event[0].e(); |
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| 163 | for(int i=0; i < int(FinalPartPos.size()); ++i){ |
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| 164 | double kt12 = ktmin; |
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| 165 | // Compute separation to the beam axis for hadronic collisions |
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| 166 | if(type == -1 || type == -2) { |
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| 167 | double temp = event[FinalPartPos[i]].pT(); |
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| 168 | kt12 = min(kt12, temp); |
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| 169 | } |
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| 170 | // Compute separation to other final state jets |
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| 171 | for(int j=i+1; j < int(FinalPartPos.size()); ++j) { |
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| 172 | double temp = kTdurham( event[FinalPartPos[i]], event[FinalPartPos[j]], |
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| 173 | type, Dparam); |
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| 174 | kt12 = min(kt12, temp); |
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| 175 | } |
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| 176 | // Keep the minimal Durham separation |
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| 177 | ktmin = min(ktmin,kt12); |
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| 178 | } |
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| 179 | |
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| 180 | // Return minimal Durham kT |
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| 181 | return ktmin; |
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| 182 | |
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| 183 | } |
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| 184 | |
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| 185 | //-------------------------------------------------------------------------- |
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| 186 | |
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| 187 | // Function to compute durham y separation from Particle input |
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| 188 | |
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| 189 | double MyMergingHooks::myKTdurham(const Particle& RadAfterBranch, |
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| 190 | const Particle& EmtAfterBranch, int Type, double D ){ |
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| 191 | |
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| 192 | // Declare return variable |
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| 193 | double ktdur; |
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| 194 | // Save 4-momenta of final state particles |
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| 195 | Vec4 jet1 = RadAfterBranch.p(); |
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| 196 | Vec4 jet2 = EmtAfterBranch.p(); |
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| 197 | |
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| 198 | if( Type == 1) { |
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| 199 | // Get angle between jets for e+e- collisions, make sure that |
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| 200 | // -1 <= cos(theta) <= 1 |
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| 201 | double costh; |
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| 202 | if (jet1.pAbs()*jet2.pAbs() <=0.) costh = 1.; |
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| 203 | else { |
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| 204 | costh = costheta(jet1,jet2); |
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| 205 | } |
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| 206 | // Calculate kt durham separation between jets for e+e- collisions |
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| 207 | ktdur = 2.0*min( pow(jet1.e(),2) , (pow(jet2.e(),2)) )*(1.0 - costh); |
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| 208 | } else if( Type == -1 ){ |
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| 209 | // Get delta_eta and cosh(Delta_eta) for hadronic collisions |
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| 210 | double eta1 = 0.5*log( (jet1.e() + jet1.pz()) / (jet1.e() - jet1.pz()) ); |
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| 211 | double eta2 = 0.5*log( (jet2.e() + jet2.pz()) / (jet2.e() - jet2.pz()) ); |
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| 212 | // Get delta_phi and cos(Delta_phi) for hadronic collisions |
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| 213 | double pt1 = sqrt( pow(jet1.px(),2) + pow(jet1.py(),2) ); |
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| 214 | double pt2 = sqrt( pow(jet2.px(),2) + pow(jet2.py(),2) ); |
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| 215 | double cosdPhi = ( jet1.px()*jet2.px() + jet1.py()*jet2.py() ) / (pt1*pt2); |
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| 216 | double dPhi = acos( cosdPhi ); |
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| 217 | // Calculate kT durham like fastjet |
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| 218 | ktdur = min( pow(pt1,2),pow(pt2,2) ) |
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| 219 | * ( pow(eta1-eta2,2) + pow(dPhi,2) ) / pow(D,2); |
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| 220 | } else if( Type == -2 ){ |
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| 221 | // Get delta_eta and cosh(Delta_eta) for hadronic collisions |
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| 222 | double eta1 = 0.5*log( (jet1.e() + jet1.pz()) / (jet1.e() - jet1.pz()) ); |
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| 223 | double eta2 = 0.5*log( (jet2.e() + jet2.pz()) / (jet2.e() - jet2.pz()) ); |
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| 224 | double coshdEta = cosh( eta1 - eta2 ); |
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| 225 | // Get delta_phi and cos(Delta_phi) for hadronic collisions |
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| 226 | double pt1 = sqrt( pow(jet1.px(),2) + pow(jet1.py(),2) ); |
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| 227 | double pt2 = sqrt( pow(jet2.px(),2) + pow(jet2.py(),2) ); |
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| 228 | double cosdPhi = ( jet1.px()*jet2.px() + jet1.py()*jet2.py() ) / (pt1*pt2); |
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| 229 | // Calculate kT durham separation "SHERPA-like" |
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| 230 | ktdur = 2.0*min( pow(pt1,2),pow(pt2,2) ) |
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| 231 | * ( coshdEta - cosdPhi ) / pow(D,2); |
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| 232 | } else { |
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| 233 | ktdur = 0.0; |
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| 234 | } |
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| 235 | // Return kT |
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| 236 | return sqrt(ktdur); |
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| 237 | } |
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| 238 | |
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| 239 | //========================================================================== |
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| 240 | |
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| 241 | // Example main programm to illustrate merging |
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| 242 | |
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| 243 | int main( int argc, char* argv[] ){ |
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| 244 | |
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| 245 | // Check that correct number of command-line arguments |
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| 246 | if (argc != 4) { |
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| 247 | cerr << " Unexpected number of command-line arguments. \n You are" |
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| 248 | << " expected to provide the arguments \n" |
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| 249 | << " 1. Input file for settings \n" |
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| 250 | << " 2. Full name of the input LHE file (with path) \n" |
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| 251 | << " 3. Path for output histogram files \n" |
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| 252 | << " Program stopped. " << endl; |
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| 253 | return 1; |
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| 254 | } |
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| 255 | |
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| 256 | Pythia pythia; |
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| 257 | |
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| 258 | // Input parameters: |
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| 259 | // 1. Input file for settings |
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| 260 | // 2. Path to input LHE file |
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| 261 | // 3. OUtput histogram path |
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| 262 | pythia.readFile(argv[1]); |
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| 263 | string iPath = string(argv[2]); |
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| 264 | string oPath = string(argv[3]); |
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| 265 | |
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| 266 | // Number of events |
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| 267 | int nEvent = pythia.mode("Main:numberOfEvents"); |
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| 268 | |
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| 269 | // Construct user inut for merging |
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| 270 | MergingHooks* myMergingHooks = new MyMergingHooks(); |
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| 271 | pythia.setMergingHooksPtr( myMergingHooks ); |
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| 272 | |
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| 273 | // For ISR regularisation off |
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| 274 | pythia.settings.forceParm("SpaceShower:pT0Ref",0.); |
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| 275 | |
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| 276 | // Declare histograms |
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| 277 | Hist histPTFirst("pT of first jet",100,0.,100.); |
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| 278 | Hist histPTSecond("pT of second jet",100,0.,100.); |
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| 279 | |
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| 280 | // Read in ME configurations |
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| 281 | pythia.init(iPath,false); |
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| 282 | |
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| 283 | if(pythia.flag("Main:showChangedSettings")) { |
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| 284 | pythia.settings.listChanged(); |
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| 285 | } |
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| 286 | |
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| 287 | // Start generation loop |
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| 288 | for( int iEvent=0; iEvent<nEvent; ++iEvent ){ |
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| 289 | |
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| 290 | // Generate next event |
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| 291 | if( ! pythia.next()) continue; |
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| 292 | |
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| 293 | // Get CKKWL weight of current event |
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| 294 | double weight = pythia.info.mergingWeight(); |
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| 295 | |
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| 296 | // Fill bins with CKKWL weight |
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| 297 | double pTfirst = pTfirstJet(pythia.event,1, 0.4); |
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| 298 | double pTsecnd = pTfirstJet(pythia.event,2, 0.4); |
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| 299 | histPTFirst.fill( pTfirst, weight); |
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| 300 | histPTSecond.fill( pTsecnd, weight); |
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| 301 | |
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| 302 | if(iEvent%1000 == 0) cout << iEvent << endl; |
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| 303 | |
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| 304 | } // end loop over events to generate |
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| 305 | |
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| 306 | // print cross section, errors |
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| 307 | pythia.stat(); |
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| 308 | |
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| 309 | // Normalise histograms |
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| 310 | double norm = 1. |
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| 311 | * pythia.info.sigmaGen() |
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| 312 | * 1./ double(nEvent); |
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| 313 | |
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| 314 | histPTFirst *= norm; |
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| 315 | histPTSecond *= norm; |
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| 316 | |
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| 317 | // Get the number of jets in the LHE file from the file name |
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| 318 | string jetsInLHEF = iPath.substr(iPath.size()-5, iPath.size()); |
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| 319 | jetsInLHEF = jetsInLHEF.substr(0, jetsInLHEF.size()-4); |
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| 320 | |
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| 321 | // Write histograms to dat file. Use "jetsInLHEF" to label the files |
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| 322 | // Once all the samples up to the maximal desired jet multiplicity from the |
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| 323 | // matrix element are run, add all histograms to produce a |
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| 324 | // matrix-element-merged prediction |
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| 325 | |
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| 326 | ofstream write; |
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| 327 | stringstream suffix; |
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| 328 | suffix << jetsInLHEF << "_wv.dat"; |
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| 329 | |
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| 330 | // Write histograms to file |
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| 331 | write.open( (char*)(oPath + "PTjet1_" + suffix.str()).c_str()); |
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| 332 | histPTFirst.table(write); |
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| 333 | write.close(); |
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| 334 | |
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| 335 | write.open( (char*)(oPath + "PTjet2_" + suffix.str()).c_str()); |
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| 336 | histPTSecond.table(write); |
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| 337 | write.close(); |
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| 338 | |
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| 339 | |
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| 340 | delete myMergingHooks; |
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| 341 | return 0; |
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| 342 | |
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| 343 | // Done |
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| 344 | } |
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