1 | // main31.cc is a part of the PYTHIA event generator. |
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2 | // Copyright (C) 2011 Mikhail Kirsanov, 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 HepMC can be interfaced to Pythia8. |
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8 | // It studies the charged multiplicity distribution at the LHC. |
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9 | // HepMC events are output to the hepmcout31.dat file. |
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10 | // Written by Mikhail Kirsanov based on main01.cc. |
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11 | |
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12 | // WARNING: typically one needs 25 MB/100 events at the LHC. |
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13 | // Therefore large event samples may be impractical. |
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14 | |
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15 | #include "Pythia.h" |
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16 | #include "HepMCInterface.h" |
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17 | |
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18 | #include "HepMC/GenEvent.h" |
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19 | #include "HepMC/IO_GenEvent.h" |
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20 | |
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21 | // Following line is a deprecated alternative, removed in recent versions |
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22 | //#include "HepMC/IO_Ascii.h" |
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23 | //#include "HepMC/IO_AsciiParticles.h" |
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24 | |
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25 | // Following line to be used with HepMC 2.04 onwards. |
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26 | #ifdef HEPMC_HAS_UNITS |
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27 | #include "HepMC/Units.h" |
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28 | #endif |
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29 | |
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30 | using namespace Pythia8; |
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31 | |
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32 | int main() { |
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33 | |
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34 | // Interface for conversion from Pythia8::Event to HepMC one. |
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35 | HepMC::I_Pythia8 ToHepMC; |
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36 | // ToHepMC.set_crash_on_problem(); |
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37 | |
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38 | // Specify file where HepMC events will be stored. |
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39 | HepMC::IO_GenEvent ascii_io("hepmcout31.dat", std::ios::out); |
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40 | // Following line is a deprecated alternative, removed in recent versions |
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41 | // HepMC::IO_Ascii ascii_io("hepmcout31.dat", std::ios::out); |
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42 | // Line below is an eye-readable one-way output, uncomment the include above |
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43 | // HepMC::IO_AsciiParticles ascii_io("hepmcout31.dat", std::ios::out); |
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44 | |
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45 | // Generator. Process selection. LHC initialization. Histogram. |
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46 | Pythia pythia; |
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47 | pythia.readString("HardQCD:all = on"); |
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48 | pythia.readString("PhaseSpace:pTHatMin = 20."); |
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49 | pythia.init( 2212, 2212, 14000.); |
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50 | Hist mult("charged multiplicity", 100, -0.5, 799.5); |
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51 | |
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52 | // Begin event loop. Generate event. Skip if error. List first one. |
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53 | for (int iEvent = 0; iEvent < 100; ++iEvent) { |
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54 | if (!pythia.next()) continue; |
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55 | if (iEvent < 1) {pythia.info.list(); pythia.event.list();} |
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56 | |
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57 | // Find number of all final charged particles and fill histogram. |
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58 | int nCharged = 0; |
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59 | for (int i = 0; i < pythia.event.size(); ++i) |
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60 | if (pythia.event[i].isFinal() && pythia.event[i].isCharged()) |
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61 | ++nCharged; |
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62 | mult.fill( nCharged ); |
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63 | |
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64 | // Construct new empty HepMC event. |
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65 | #ifdef HEPMC_HAS_UNITS |
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66 | // This form with arguments is only meaningful for HepMC 2.04 onwards, |
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67 | // and even then unnecessary if HepMC was built with GeV and mm as units.. |
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68 | HepMC::GenEvent* hepmcevt = new HepMC::GenEvent( |
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69 | HepMC::Units::GEV, HepMC::Units::MM); |
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70 | #else |
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71 | // This form is needed for backwards compatibility. |
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72 | // In HepMCInterface.cc a conversion from GeV to MeV will be done. |
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73 | HepMC::GenEvent* hepmcevt = new HepMC::GenEvent(); |
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74 | #endif |
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75 | |
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76 | // Fill HepMC event, including PDF info. |
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77 | ToHepMC.fill_next_event( pythia, hepmcevt ); |
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78 | // This alternative older method fills event, without PDF info. |
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79 | // ToHepMC.fill_next_event( pythia.event, hepmcevt ); |
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80 | |
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81 | // Write the HepMC event to file. Done with it. |
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82 | ascii_io << hepmcevt; |
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83 | delete hepmcevt; |
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84 | |
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85 | // End of event loop. Statistics. Histogram. |
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86 | } |
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87 | pythia.statistics(); |
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88 | cout << mult; |
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89 | |
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90 | // Done. |
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91 | return 0; |
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92 | } |
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