## main112

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    // main112.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.

    // Keywords:
    //            Basic usage
    //            Z production
    //            Tevatron
    //            Matplotlib

    // This is a simple test program, equivalent with main102,
    // for the pT_Z spectrum at the Tevatron, but with plotting of histogram.
    // Assuming that you have Python3 installed on your platform, do as follows.
    // After the program has run, type "python3 plot112.py" (without the " ")
    // in a terminal window, and open "fig112.pdf" in a PDF viewer.

    #include "Pythia8/Pythia.h"

    using namespace Pythia8;

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

    int main() {

      // Generator. Process selection.
      Pythia pythia;
      pythia.readString("Beams:idB = -2212");
      pythia.readString("Beams:eCM = 1960.");
      pythia.readString("WeakSingleBoson:ffbar2gmZ = on");
      pythia.readString("PhaseSpace:mHatMin = 80.");
      pythia.readString("PhaseSpace:mHatMax = 120.");

      // Tevatron initialization. Histogram.
      // If Pythia fails to initialize, exit with error.
      if (!pythia.init()) return 1;
      Hist pTZ("dN/dpTZ", 100, 0., 100.);

      // Begin event loop. Generate event. Skip if error.
      for (int iEvent = 0; iEvent < 1000; ++iEvent) {
        if (!pythia.next()) continue;

        // Loop over particles in event. Find last Z0 copy. Fill its pT.
        int iZ = 0;
        for (int i = 0; i < pythia.event.size(); ++i)
          if (pythia.event[i].id() == 23) iZ = i;
        pTZ.fill( pythia.event[iZ].pT() );

      // End of event loop. Statistics. Output normalized histogram.
      }
      pythia.stat();
      pTZ /= 1000;
      cout << pTZ;

      // Write Python code that can generate a PDF file with the spectrum.
      // Use plotFrame when a frame should only contain one histogram.
      // Colours and other choices can be omitted, but are shown as illustration.
      HistPlot hpl("plot112");
      hpl.plotFrame("fig112", pTZ, "Z transverse momentum", "$p_{\\perp}$ (GeV)",
        "$\\mathrm{d}N/\\mathrm{d}p_{\\perp}$ (1/GeV)", "-");

      // Done
      return 0;
    }