## main508

Back to index.

    // main508.cc is a part of the PYTHIA event generator.
    // Copyright (C) 2026 Torbjorn Sjostrand.
    // PYTHIA is licenced under the GNU GPL v2 or later, see COPYING for details.
    // Please respect the MCnet Guidelines, see GUIDELINES for details.

    // Authors:
    //            Nishita Desai

    // Keywords:
    //            Basic usage
    //            BSM
    //            Supersymmetry

    // This is a simple test program.
    // It illustrates how to run SUSY processes in Pythia8.
    // All input is specified in the main507.cmnd file.

    #include "Pythia8/Pythia.h"

    using namespace Pythia8;

    //==========================================================================

    int main() {

      // Generator. Shorthand for the event.
      Pythia pythia;
      Event& event = pythia.event;

      // Read in commands from external file.
      pythia.readFile("main508.cmnd");

      // Extract settings to be used in the main program.
      int nEvent   = pythia.mode("Main:numberOfEvents");
      int nAbort   = pythia.mode("Main:timesAllowErrors");

      // If Pythia fails to initialize, exit with error.
      if (!pythia.init()) return 1;

      // Set lifetime of long-lived particle.
      int iLLP = 56; // Change to 57 for X+ and 59 for X++
      cout << "Lifetime [mm] = " << scientific << pythia.particleData.tau0(iLLP)
           << endl;

      // Histograms.
      Hist life("Decay lifetime [mm]",100,0.,100.);

      // Begin event loop.
      int iAbort = 0;
      for (int iEvent = 0; iEvent < nEvent; ++iEvent) {

        // Generate events. Quit if failure.
        if (!pythia.next()) {
          event.list();
          if (++iAbort < nAbort) continue;
          cout << " Event generation aborted prematurely, owing to error!\n";
          break;
        }

        life.fill(event[5].tau());

      // End of event loop.
      }

      // Final statistics and histogram output.
      pythia.stat();
      cout << life << endl;

      return 0;
    }