1 | // main18.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 is a simple test program. |
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7 | // It illustrates how to write an event filter. |
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8 | // No new functionality is involved - all could be done in the main program |
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9 | // - but the division of tasks may be more convenient for recurrent cuts. |
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10 | |
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11 | #include "Pythia.h" |
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12 | |
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13 | using namespace Pythia8; |
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14 | |
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15 | //========================================================================== |
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16 | |
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17 | // The EventFilter class. |
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18 | |
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19 | // The constructor takes the following arguments |
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20 | // select = 1 : keep only final particles. |
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21 | // = 2 : keep only final visible particles (i.e. not neutrinos). |
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22 | // = 3 : keep only final charged particles. |
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23 | // etaMax (default = 50) : keep only particles with pseudorapidity |
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24 | // |eta| < etaMax. |
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25 | // pTminCharged (default = 0) : keep a charged particle only if |
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26 | // its transverse momentum pT < pTminCharged. |
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27 | // pTminNeutral (default = 0) : keep a neutral particle only if |
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28 | // its transverse momentum pT < pTminNeutral. |
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29 | |
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30 | // Main methods: |
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31 | // filter( event) takes an event record as input and analyzes it. |
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32 | // size() returns the number of particles kept. |
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33 | // index(i) returns the index in the full event of the i'th kept particle. |
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34 | // particlePtr(i) returns a pointer to the i'th kept particle. |
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35 | // particleRef(i) returns a reference to the i'th kept particle. |
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36 | // list() gives a listing of the kept particles only. |
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37 | |
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38 | class EventFilter { |
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39 | |
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40 | public: |
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41 | |
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42 | // Constructor sets properties of filter. |
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43 | EventFilter( int selectIn, double etaMaxIn = 50., |
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44 | double pTminChargedIn = 0., double pTminNeutralIn = 0.) |
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45 | : select(selectIn), etaMax(etaMaxIn), pTminCharged(pTminChargedIn), |
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46 | pTminNeutral(pTminNeutralIn) {} |
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47 | |
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48 | // Analysis of each new event to find acceptable particles. |
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49 | void filter(Event& event); |
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50 | |
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51 | // Return size of array, and index of a particle. |
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52 | int size() const {return keptPtrs.size();} |
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53 | int index(int i) const {return keptIndx[i];} |
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54 | |
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55 | // Return pointer or reference to a particle. |
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56 | Particle* particlePtr(int i) {return keptPtrs[i];} |
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57 | Particle& particleRef(int i) {return *keptPtrs[i];} |
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58 | |
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59 | // List kept particles only. |
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60 | void list(ostream& os = cout); |
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61 | |
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62 | private: |
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63 | |
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64 | // Filter properties, set by constructor. |
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65 | int select; |
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66 | double etaMax, pTminCharged, pTminNeutral; |
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67 | |
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68 | // Kept particle indices and pointers, referring to original event. |
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69 | vector<int> keptIndx; |
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70 | vector<Particle*> keptPtrs; |
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71 | |
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72 | }; |
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73 | |
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74 | //-------------------------------------------------------------------------- |
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75 | |
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76 | // The filter method. |
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77 | |
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78 | void EventFilter::filter(Event& event) { |
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79 | |
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80 | // Reset arrays in preparation for new event. |
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81 | keptIndx.resize(0); |
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82 | keptPtrs.resize(0); |
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83 | |
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84 | // Loop over all particles in the event record. |
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85 | for (int i = 0; i < event.size(); ++i) { |
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86 | |
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87 | // Skip if particle kind selection criteria not fulfilled. |
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88 | if (!event[i].isFinal()) continue; |
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89 | if (select == 2 && !event[i].isVisible()) continue; |
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90 | bool isCharged = event[i].isCharged(); |
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91 | if (select == 3 && !isCharged) continue; |
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92 | |
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93 | // Skip if too large pseudorapidity. |
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94 | if (abs(event[i].eta()) > etaMax) continue; |
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95 | |
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96 | // Skip if too small pT. |
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97 | if (isCharged && event[i].pT() < pTminCharged) continue; |
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98 | else if (!isCharged && event[i].pT() < pTminNeutral) continue; |
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99 | |
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100 | // Add particle to vectors of indices and pointers. |
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101 | keptIndx.push_back( i ); |
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102 | keptPtrs.push_back( &event[i] ); |
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103 | |
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104 | // End of particle loop. Done. |
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105 | } |
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106 | |
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107 | } |
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108 | |
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109 | //-------------------------------------------------------------------------- |
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110 | |
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111 | // The list method: downscaled version of Event::list. |
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112 | |
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113 | void EventFilter::list(ostream& os) { |
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114 | |
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115 | // Header. |
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116 | os << "\n -------- PYTHIA Event Listing (filtered) ------------------" |
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117 | << "-----------------------------------------------------------------" |
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118 | << "----\n \n no id name status mothers " |
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119 | << " daughters colours p_x p_y p_z e " |
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120 | << " m \n"; |
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121 | |
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122 | // At high energy switch to scientific format for momenta. |
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123 | double eSum = 0.; |
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124 | for (int iKept = 0; iKept < size(); ++iKept) eSum += keptPtrs[iKept]->e(); |
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125 | bool useFixed = (eSum < 1e5); |
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126 | |
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127 | // Listing of kept particles in event. |
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128 | for (int iKept = 0; iKept < size(); ++iKept) { |
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129 | int i = keptIndx[iKept]; |
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130 | Particle& pt = *keptPtrs[iKept]; |
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131 | |
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132 | // Basic line for a particle, always printed. |
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133 | os << setw(6) << i << setw(10) << pt.id() << " " << left |
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134 | << setw(18) << pt.nameWithStatus(18) << right << setw(4) |
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135 | << pt.status() << setw(6) << pt.mother1() << setw(6) |
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136 | << pt.mother2() << setw(6) << pt.daughter1() << setw(6) |
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137 | << pt.daughter2() << setw(6) << pt.col() << setw(6) << pt.acol() |
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138 | << ( (useFixed) ? fixed : scientific ) << setprecision(3) |
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139 | << setw(11) << pt.px() << setw(11) << pt.py() << setw(11) |
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140 | << pt.pz() << setw(11) << pt.e() << setw(11) << pt.m() << "\n"; |
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141 | } |
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142 | |
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143 | // Listing finished. |
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144 | os << "\n -------- End PYTHIA Event Listing ----------------------------" |
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145 | << "-------------------------------------------------------------------" |
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146 | << endl; |
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147 | } |
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148 | |
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149 | |
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150 | //========================================================================== |
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151 | |
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152 | // Use the EventFilter method to plot some event properties. |
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153 | |
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154 | int main() { |
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155 | |
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156 | // Number of events to generate, to list, to allow aborts. |
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157 | int nEvent = 100; |
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158 | int nList = 1; |
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159 | int nAbort = 3; |
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160 | |
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161 | // Declare generator. |
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162 | Pythia pythia; |
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163 | |
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164 | // Hard QCD events with pThat > 100. |
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165 | pythia.readString("HardQCD:all = on"); |
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166 | pythia.readString("PhaseSpace:pTHatMin = 100."); |
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167 | |
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168 | // No automatic event listings - do it manually below. |
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169 | pythia.readString("Next:numberShowInfo = 0"); |
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170 | pythia.readString("Next:numberShowProcess = 0"); |
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171 | pythia.readString("Next:numberShowEvent = 0"); |
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172 | |
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173 | // Initialization for LHC. |
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174 | pythia.init(); |
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175 | |
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176 | // Values for filter. |
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177 | int select = 3; |
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178 | double etaMax = 3.; |
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179 | double pTminChg = 1.; |
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180 | |
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181 | // Declare Event Filter according to specification. |
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182 | EventFilter filter( select, etaMax, pTminChg); |
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183 | |
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184 | // Histograms. |
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185 | Hist nCharged( "selected charged multiplicity", 100, -0.5, 199.5); |
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186 | Hist etaCharged( "selected charged eta distribution", 100, -5.0, 5.0); |
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187 | Hist pTCharged( "selected charged pT distribution", 100, 0.0, 50.0); |
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188 | |
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189 | // Begin event loop. |
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190 | int iAbort = 0; |
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191 | for (int iEvent = 0; iEvent < nEvent; ++iEvent) { |
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192 | |
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193 | // Generate events. Quit if too many failures. |
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194 | if (!pythia.next()) { |
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195 | if (++iAbort < nAbort) continue; |
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196 | cout << " Event generation aborted prematurely, owing to error!\n"; |
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197 | break; |
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198 | } |
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199 | |
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200 | // Find final charged particles with |eta| < 3 and pT > 1 GeV. |
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201 | filter.filter( pythia.event); |
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202 | |
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203 | // List first few events, both complete and after filtering. |
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204 | if (iEvent < nList) { |
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205 | pythia.info.list(); |
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206 | pythia.process.list(); |
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207 | pythia.event.list(); |
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208 | filter.list(); |
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209 | } |
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210 | |
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211 | // Analyze selected particle sample. |
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212 | nCharged.fill( filter.size() ); |
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213 | for (int i = 0; i < filter.size(); ++i) { |
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214 | // Use both reference and pointer notation to illustrate freedom. |
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215 | etaCharged.fill( filter.particleRef(i).eta() ); |
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216 | pTCharged.fill( filter.particlePtr(i)->pT() ); |
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217 | } |
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218 | |
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219 | // End of event loop. |
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220 | } |
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221 | |
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222 | // Final statistics. |
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223 | pythia.stat(); |
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224 | |
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225 | // Histograms. |
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226 | cout << nCharged << etaCharged << pTCharged; |
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227 | |
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228 | // Done. |
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229 | return 0; |
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230 | } |
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