// main505.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: extra dimensions; BSM

// Kaluza-Klein gamma*/Z resonances in TeV-sized extra dimensions.

#include <assert.h>
#include <time.h>
#include <sstream>

#include "Pythia8/Pythia.h"
using namespace Pythia8;

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

int main() {

  // Generator.
  Pythia pythia;
  ParticleData& pdt = pythia.particleData;

  // Pick new random number seed for each run, based on clock.
  pythia.readString("Random:setSeed = on");
  pythia.readString("Random:seed = 0");

  // Process selection.
  // ANY COMBINATION OF THE PROCESSES FLAGS BELOW IS ALLOWED
  // HERE WE SWITCH ON ONLY THE MU+MU- FINAL STATE.
  // TO SWITCH ALL POSSIBLE FINAL STATES ON, UNCOMMENT ALL
  // THE RELEVANT LINES BELOW:
  //pythia.readString("ExtraDimensionsTEV:ffbar2e+e- = on");
  pythia.readString("ExtraDimensionsTEV:ffbar2mu+mu- = on");
  //pythia.readString("ExtraDimensionsTEV:ffbar2tau+tau- = on");
  //pythia.readString("ExtraDimensionsTEV:ffbar2uubar = on");
  //pythia.readString("ExtraDimensionsTEV:ffbar2ddbar = on");
  //pythia.readString("ExtraDimensionsTEV:ffbar2ccbar = on");
  //pythia.readString("ExtraDimensionsTEV:ffbar2ssbar = on");
  //pythia.readString("ExtraDimensionsTEV:ffbar2bbbar = on");
  //pythia.readString("ExtraDimensionsTEV:ffbar2ttbar = on");
  //pythia.readString("ExtraDimensionsTEV:ffbar2nuenuebar = on");
  //pythia.readString("ExtraDimensionsTEV:ffbar2numunumubar = on");
  //pythia.readString("ExtraDimensionsTEV:ffbar2nutaunutaubar = on");

  // Pick KK mass.
  double newMass = 4000.; // GeV
  cout << "|-------------------------" << endl;
  cout << "| KK mass is: " << newMass << endl;
  cout << "|-------------------------" << endl;
  stringstream strm;
  string sNewMass, sNewWidth, sNewLowBound, sNewHighBound;

  // Manually set the mass and therefore the width
  // and the phase space for the sampling
  strm.clear();
  strm << newMass;
  strm >> sNewMass;
  strm.clear();
  strm << newMass / pdt.m0(5000023) * pdt.mWidth(5000023);
  strm >> sNewWidth;
  strm.clear();
  strm << newMass/4.;
  strm >> sNewLowBound;
  strm.clear();
  strm << newMass*2.;
  strm >> sNewHighBound;

  // Feed in KK state information and other generation specifics.
  pythia.readString("5000023:m0 = " + sNewMass);
  pythia.readString("5000023:mWidth = " + sNewWidth);
  pythia.readString("5000023:mMin = " + sNewLowBound);
  pythia.readString("5000023:mMax = " + sNewHighBound);
  //////////////////////////////////////////////////////////////////////////
  pythia.readString("5000023:isResonance = false"); // THIS IS MANDATORY  //
  //////////////////////////////////////////////////////////////////////////
  // 0=(gm+Z), 1=(gm), 2=(Z), 3=(gm+Z+gmKK+ZKK), 4=(m+Z+gmKK), 5=(m+Z+ZKK)
  pythia.readString("ExtraDimensionsTEV:gmZmode = 3");
  // min=0, max=100, default=10
  pythia.readString("ExtraDimensionsTEV:nMax = 100");
  pythia.readString("ExtraDimensionsTEV:mStar = " + sNewMass);
  pythia.readString("PhaseSpace:mHatMin = " + sNewLowBound);
  pythia.readString("PhaseSpace:mHatMax = " + sNewHighBound);

  // Initialize for LHC.
  pythia.readString("Beams:eCM = 14000.");

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

  // Histograms.
  Hist mHatHisto("dN/dmHat", 50, newMass/4., newMass*2.);
  Hist pTmuHisto("(dN/dpT)_mu^-", 50, 1., 2501.);

  vector<int> moms;

  // Measure the cpu runtime.
  clock_t start, stop;
  double t = 0.0;
  // Depending on operating system, either of lines below gives warning.
  //assert((start = clock()) != -1); // Start timer; clock_t signed.
  //assert((start = clock()) != -1u); // Start timer; clock_t unsigned.
  // Simpler option, not using assert.
  start = clock();

  // Begin event loop. Generate event. Skip if error. List first one.
  for (int iEvent = 0 ; iEvent < 500 ; ++iEvent) {
    if (!pythia.next()) continue;

    // Begin event analysis.
    bool isZ = false;
    bool ismu = false;
    int iZ = 0;
    int imu = 0;
    for (int i = 0 ; i < pythia.event.size() ; ++i) {
      // find the most recent Z
      if (pythia.event[i].id() == 5000023) {
        iZ = i;
        isZ = true;
      }
      // find the final muon who's first mother is the Z
      if (pythia.event[i].id() == 13 && pythia.event[i].isFinal()) {
        moms.clear();
        moms = pythia.event[i].motherList();
        for (int m = 0 ; m < int(moms.size()) ; m++) {
          if( pythia.event[ moms[m] ].id() == 5000023 ) {
            imu = i;
            ismu = true;
            break;
          } // end if 5000023
        } // end for moms.size()
      } // end if final muon
    } // end for event.size()
    if(isZ && ismu) {
      mHatHisto.fill( pythia.event[iZ].m() );
      pTmuHisto.fill( pythia.event[imu].pT() );
    }
    if(iEvent%10 == 0) cout << "Event: " << iEvent << endl << std::flush;
  } // end for iEvent<500

  // Done. Print results.
  stop = clock(); // Stop timer
  t = (double) (stop-start)/CLOCKS_PER_SEC;

  pythia.stat();
  cout << mHatHisto;
  cout << pTmuHisto;

  cout << "\n" << "|----------------------------------------|" << endl;
  cout << "| CPU Runtime = " << t << " sec" << endl;
  cout << "|----------------------------------------|" << "\n" << endl;

  return 0;
}
