photos_standalone_example.cxx

/**
 * Example of photos usage.
 * Events are loaded from pre-generated set featuring Z0 -> tau+ tau- decays
 * and processed by photos.
 *
 * @author Tomasz Przedzinski
 * @date 17 July 2010
 */

//HepMC header files
#include "HepMC/IO_GenEvent.h"

//PHOTOS header files
#include "Photos/Photos.h"
#include "Photos/PhotosHepMCEvent.h"
#include "Photos/Log.h"

using namespace std;
using namespace Photospp;

int EventsToCheck=20;

// elementary test of HepMC typically executed before
// detector simulation based on http://home.fnal.gov/~mrenna/HCPSS/HCPSShepmc.html
// similar test was performed in Fortran
// we perform it before and after Photos (for the first several events)
void checkMomentumConservationInEvent(HepMC::GenEvent *evt)
{
        //cout<<"List of stable particles: "<<endl;

        double px=0.0,py=0.0,pz=0.0,e=0.0;
        
        for ( HepMC::GenEvent::particle_const_iterator p = evt->particles_begin();
              p != evt->particles_end(); ++p )
        {
                if( (*p)->status() == 1 )
                {
                        HepMC::FourVector m = (*p)->momentum();
                        px+=m.px();
                        py+=m.py();
                        pz+=m.pz();
                        e +=m.e();
                        //(*p)->print();
                }
        }
  cout.precision(6);
  cout.setf(ios_base::floatfield);
        cout<<endl<<"Vector Sum: "<<px<<" "<<py<<" "<<pz<<" "<<e<<endl;
}

int main()
{
        HepMC::IO_GenEvent file("photos_standalone_example.dat",std::ios::in);

        Photos::initialize();
        Photos::setInfraredCutOff(0.001/200);

        int photonAdded=0,twoAdded=0,moreAdded=0,evtCount=0;
        // Begin event loop. Generate event.
        while(true)
        {
                // Create event
                HepMC::GenEvent *HepMCEvt = new HepMC::GenEvent();
                file.fill_next_event(HepMCEvt);
                if(file.rdstate()) break;
                evtCount++;
                int buf = -HepMCEvt->particles_size();

                //cout << "BEFORE:"<<endl;
                //HepMCEvt->print();

                if(evtCount<EventsToCheck)
                {
                        cout<<"                                          "<<endl;
                        cout<<"Momentum conservation chceck BEFORE/AFTER Photos"<<endl;
                        checkMomentumConservationInEvent(HepMCEvt);
                }

                // Process by photos
                PhotosHepMCEvent evt(HepMCEvt);
                evt.process();

                if(evtCount<EventsToCheck)
                {
                        checkMomentumConservationInEvent(HepMCEvt);
                }

                buf+=HepMCEvt->particles_size();
                if(buf==1)      photonAdded++;
                else if(buf==2) twoAdded++;
                else if(buf>2)  moreAdded++;

                //cout << "AFTER:"<<endl;
                //HepMCEvt->print();

                //clean up
                delete HepMCEvt;
        }

        // Print results
        cout.precision(2);
        cout.setf(ios::fixed);
        cout<<endl;
        if(evtCount==0)
        {
                cout<<"Something went wrong with the input file: photos_standalone_example.dat"<<endl;
                cout<<"No events were processed."<<endl<<endl;
                return 0;
        }
        cout<<"Summary (whole event processing):"<<endl;
        cout<<evtCount   <<"\tevents processed"<<endl;
        cout<<photonAdded<<"\ttimes one photon added to the event           \t("<<(photonAdded*100./evtCount)<<"%)"<<endl;
        cout<<twoAdded   <<"\ttimes two photons added to the event          \t("<<(twoAdded*100./evtCount)<<"%)"<<endl;
        cout<<moreAdded  <<"\ttimes more than two photons added to the event\t("<<(moreAdded*100./evtCount)<<"%)"<<endl<<endl;
        cout<<"(Contrary to results from MC-Tester, these values are technical and infrared unstable)"<<endl<<endl;
}