[1] | 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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