PhotosInterface.cc

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#include <iostream>

// #include "GeneratorInterface/Pythia6Interface/interface/Pythia6Service.h"

#include "GeneratorInterface/ExternalDecays/interface/PhotosInterface.h"

#include "FWCore/ServiceRegistry/interface/Service.h"
// #include "FWCore/Utilities/interface/RandomNumberGenerator.h"
#include "GeneratorInterface/ExternalDecays/interface/DecayRandomEngine.h"

#include "HepMC/GenEvent.h"
#include "HepMC/IO_HEPEVT.h"
#include "HepMC/HEPEVT_Wrapper.h"

using namespace gen;
using namespace edm;
using namespace std;

// const int NMXHEP = HepMC::HEPEVT_Wrapper::max_number_entries() ;

extern "C"{

   void phoini_( void );
   void photos_( int& );

   double phoran_(int *idummy)
   {
      return decayRandomEngine->flat();
   }
/*
   double phoranc_(int *idummy)
   {
      return decayRandomEngine->flat();
   }
*/

   extern struct {
      // bool qedrad[NMXHEP];
      bool qedrad[4000]; // hardcoded for now...
   } phoqed_;

}


PhotosInterface::PhotosInterface()
   : fOnlyPDG(-1)
{
   fSpecialSettings.push_back("QED-brem-off:all");
   fAvoidTauLeptonicDecays = false;
   fIsInitialized = false; 
}

PhotosInterface::PhotosInterface( const edm::ParameterSet& )
   : fOnlyPDG(-1)
{
   fSpecialSettings.push_back("QED-brem-off:all");
   fIsInitialized = false;
}

/*  -->
void PhotosInterface::configureOnlyFor( int ipdg )
{

   fOnlyPDG = ipdg;
   std::ostringstream command;
   command << "QED-brem-off:" << fOnlyPDG ;
   fSpecialSettings.clear();
   fSpecialSettings.push_back( command.str() );
   
   return;

}
*/

void PhotosInterface::init()
{
   
   if ( fIsInitialized ) return; // do init only once
   
   phoini_();
   
   fIsInitialized = true; 

   return;
}

HepMC::GenEvent* PhotosInterface::apply( HepMC::GenEvent* evt )
{
   
   // event record convertor 
   // ...well, I'm not sure we need it here, 
   // as we do it by hands, only part of the record
   //
   // HepMC::IO_HEPEVT conv;
   
   if ( !fIsInitialized ) return evt; // conv.read_next_event();
   
   // cross-check printout HepMC::GenEvent
   //
   //evt->print();
   
   // int numPartBefore = HepMC::HEPEVT_Wrapper::number_entries();
   // HepMC::HEPEVT_Wrapper::print_hepevt();
   
   // loop over HepMC::GenEvent, find vertices

   // std::vector<int> barcodes;   
   // std::vector<Scaling> scaleFactors;
   
   fScaleFactors.clear();
   
   for ( int ip=0; ip<evt->particles_size(); ip++ )
   {
      fScaleFactors.push_back( Scaling(HepMC::ThreeVector(1.,1.,1.),1) );
      phoqed_.qedrad[ip]=true;
   }
   
   
   // variables for special treatment of tau leptonic decays
   //
   bool tau_leptonic_decay = false;
   int iTauDescCounter = 0;
   int nTauDesc = 0;
   
   for ( int iv=1; iv<=evt->vertices_size(); iv++ )
   {
      
      HepMC::GenVertex* vtx = evt->barcode_to_vertex( -iv ) ;
      if ( vtx->particles_in_size() != 1 ) continue; // more complex than we need
      if ( vtx->particles_out_size() <= 0 ) continue; // no outcoming particles
      // --> if ( fOnlyPDG !=-1 && (*(vtx->particles_in_const_begin()))->pdg_id() == fOnlyPDG ) continue;
      // now find at least one "legal" daughter
      bool legalVtx = false;
      for ( HepMC::GenVertex::particle_iterator pitr=vtx->particles_begin(HepMC::children);
            pitr != vtx->particles_end(HepMC::children); ++pitr) 
      {
         if ( (*pitr)->status() == 1 || (*pitr)->end_vertex() )
     {
        // OK, legal already !
        legalVtx = true;
        break;
     }
      }
      
      if ( !legalVtx ) continue;
            
      // now do all the loops again
      //
      // first, flush out HEPEVT & tmp barcode storage
      //
      HepMC::HEPEVT_Wrapper::zero_everything();
      fBarcodes.clear();
      
      // add incoming particle
      //
      int index = 1;      
      HepMC::HEPEVT_Wrapper::set_id( index, (*(vtx->particles_in_const_begin()))->pdg_id() );
      HepMC::FourVector vec4;
      vec4 = (*(vtx->particles_in_const_begin()))->momentum();
      HepMC::HEPEVT_Wrapper::set_momentum( index, vec4.x(), vec4.y(), vec4.z(), vec4.e() );
      HepMC::HEPEVT_Wrapper::set_mass( index, (*(vtx->particles_in_const_begin()))->generated_mass() );
      HepMC::HEPEVT_Wrapper::set_position( index, vtx->position().x(), vtx->position().y(),
                                                  vtx->position().z(), vtx->position().t() );
      HepMC::HEPEVT_Wrapper::set_status( index, (*(vtx->particles_in_const_begin()))->status() );
      HepMC::HEPEVT_Wrapper::set_parents( index, 0, 0 );
      fBarcodes.push_back( (*(vtx->particles_in_const_begin()))->barcode() );
                  
      // special case: avoid tau leptonic decays
      //

      if ( fAvoidTauLeptonicDecays && !tau_leptonic_decay && abs((*(vtx->particles_in_const_begin()))->pdg_id()) == 15 )
      {      
         for ( HepMC::GenVertex::particle_iterator pitr=vtx->particles_begin(HepMC::children);
               pitr != vtx->particles_end(HepMC::children); ++pitr) 
         {
        if ( abs((*pitr)->pdg_id()) == 11 || abs((*pitr)->pdg_id()) == 13 ) // leptonic decay !!!
                                                                            // do brem off tau but NOT off decay products
        {
           tau_leptonic_decay = true;
           break;
        }    
         }
         if ( vtx->particles_begin(HepMC::children) == vtx->particles_begin(HepMC::descendants) && 
              vtx->particles_end(HepMC::children) == vtx->particles_end(HepMC::descendants) ) 
         {
        nTauDesc = vtx->particles_out_size();
         }
     else
     {
            for ( HepMC::GenVertex::particle_iterator pitr1=vtx->particles_begin(HepMC::children);
                  pitr1 != vtx->particles_end(HepMC::children); ++pitr1) 
            {
           nTauDesc++;
        }
     }
         // this is just the 1st tau in the branch, so it's allowed to emit
     phoqed_.qedrad[index-1]=true;
     iTauDescCounter = 0;
      }
     
      // check if mother has ever been "altered" !
      //
      int mbcode =  (*(vtx->particles_in_const_begin()))->barcode();
      
      // add outcoming particles (decay products)
      //
      int lastDau = 1;
      for ( HepMC::GenVertex::particle_iterator pitr=vtx->particles_begin(HepMC::children);
            pitr != vtx->particles_end(HepMC::children); ++pitr) 
      {
         if ( fScaleFactors[mbcode-1].flag != 1. )
     {
        // yes, mother has been changed - adjust daughters
        
        vec4 = (*pitr)->momentum();
        double mass2 = vec4.m2();
        double pxn = vec4.px() * fScaleFactors[mbcode-1].weights.x();
        double pyn = vec4.py() * fScaleFactors[mbcode-1].weights.y();
        double pzn = vec4.pz() * fScaleFactors[mbcode-1].weights.z();
        double en  = sqrt( pxn*pxn + pyn*pyn + pzn*pzn + mass2 );
        (*pitr)->set_momentum( HepMC::FourVector(pxn,pyn,pzn,en) );
        int curbcode = (*pitr)->barcode();
        double scale = fScaleFactors[curbcode-1].weights.x();
        fScaleFactors[curbcode-1].weights.setX( scale*fScaleFactors[mbcode-1].weights.x() );
        scale = fScaleFactors[curbcode-1].weights.y();
        fScaleFactors[curbcode-1].weights.setY( scale*fScaleFactors[mbcode-1].weights.y() );
        scale = fScaleFactors[curbcode-1].weights.z();
        fScaleFactors[curbcode-1].weights.setZ( scale*fScaleFactors[mbcode-1].weights.z() );
        fScaleFactors[curbcode-1].flag = 0;
     }
             
     if ( (*pitr)->status() == 1 || (*pitr)->end_vertex() )
     {
        index++;
        vec4 = (*pitr)->momentum();
        HepMC::HEPEVT_Wrapper::set_id( index, (*pitr)->pdg_id() );
            HepMC::HEPEVT_Wrapper::set_momentum( index, vec4.x(), vec4.y(), vec4.z(), vec4.e() );
        HepMC::HEPEVT_Wrapper::set_mass( index, (*pitr)->generated_mass() );
        vec4 = (*pitr)->production_vertex()->position();
            HepMC::HEPEVT_Wrapper::set_position( index, vec4.x(), vec4.y(), vec4.z(), vec4.t() );
        HepMC::HEPEVT_Wrapper::set_status( index, (*pitr)->status() );
        HepMC::HEPEVT_Wrapper::set_parents( index, 1, 1 );
        fBarcodes.push_back( (*pitr)->barcode() );
        lastDau++;
        if ( fAvoidTauLeptonicDecays && tau_leptonic_decay )
        {
           phoqed_.qedrad[index-1]=false;
           iTauDescCounter++;
        }
     }
      }
            
      // store, further to set NHEP in HEPEVT
      //
      int nentries = index;
      
      // reset master pointer to mother
      index = 1;
      HepMC::HEPEVT_Wrapper::set_children ( index, 2, lastDau ); // FIXME: need to check 
                                                                 // if last daughter>=2 !!!
      
      // finally, set number of entries (NHEP) in HEPEVT
      //
      HepMC::HEPEVT_Wrapper::set_number_entries( nentries );

      // cross-check printout HEPEVT
      // HepMC::HEPEVT_Wrapper::print_hepevt();
     
      // OK, 1-level vertex is formed - now, call PHOTOS
      //
      photos_( index ) ;
      
      // another cross-check printout HEPEVT - after photos
      // HepMC::HEPEVT_Wrapper::print_hepevt();


      // now check if something has been generated
      //
      attachParticles( evt, vtx, nentries );

      // ugh, done with this vertex !
      
      // now some resets
      //
      if ( fAvoidTauLeptonicDecays && tau_leptonic_decay && iTauDescCounter == nTauDesc ) // treated tau leptonic decay and have come to the last descendent
      {
         tau_leptonic_decay = false;
      }
   
   }
   
   // restore event number in HEPEVT (safety measure, somehow needed by Hw6)
   HepMC::HEPEVT_Wrapper::set_event_number( evt->event_number() );

   // cross-check printout MODIFIED HepMC::GenEvent
   // evt->print();

   // return conv.read_next_event();
   return evt;
      
}

void PhotosInterface::attachParticles( HepMC::GenEvent* evt, HepMC::GenVertex* vtx, int nentries )
{

   if ( HepMC::HEPEVT_Wrapper::number_entries() > nentries ) 
   {
         // yes, need all corrections and adjustments -
     // figure out how many photons and what particles in 
     // the decay branch have changes;
     // also, follow up each one and correct accordingly;
     // at the same time, add photon(s) to the GenVertex
     //  
     int largestBarcode = -1;
     int Nbcodes = fBarcodes.size();
     for ( int ip=1; ip<Nbcodes; ip++ )
     {
        int bcode = fBarcodes[ip];
        HepMC::GenParticle* prt = evt->barcode_to_particle( bcode );
        if ( bcode > largestBarcode ) largestBarcode = bcode;
        double px = HepMC::HEPEVT_Wrapper::px(ip+1);
        double py = HepMC::HEPEVT_Wrapper::py(ip+1);
        double pz = HepMC::HEPEVT_Wrapper::pz(ip+1);
        double e  = HepMC::HEPEVT_Wrapper::e(ip+1);
        HepMC::FourVector mom4 = prt->momentum();
        //double porg = sqrt( mom4.px()*mom4.px() 
         //                 + mom4.py()*mom4.py() 
        //        + mom4.pz()*mom4.pz() ) ;
        //double pnew = sqrt( px*px + py*py + pz*pz );
        double scale = fScaleFactors[bcode-1].weights.x();
        fScaleFactors[bcode-1].weights.setX( scale*(px/mom4.px()) ); 
        scale = fScaleFactors[bcode-1].weights.y();
        fScaleFactors[bcode-1].weights.setY( scale*(py/mom4.py()) ); 
        scale = fScaleFactors[bcode-1].weights.z();
        fScaleFactors[bcode-1].weights.setZ( scale*(pz/mom4.pz()) );
        fScaleFactors[bcode-1].flag = 0; 
        
        prt->set_momentum( HepMC::FourVector(px,py,pz,e) );
        
        // we do NOT adjust chaldren, etc., here - because we do it 
        // above, based on whether mother (incoming particles) has
        // ever been modified
     
     }
         
     int newlyGen =  HepMC::HEPEVT_Wrapper::number_entries() - nentries;
     
     if ( largestBarcode < evt->particles_size() )
     {
        // need to adjust barcodes down from the affected vertex/particles
        // such that we "free up" barcodes for newly generated photons
        // in the middle of the event record
        //
        for ( int ipp=evt->particles_size(); ipp>largestBarcode; ipp-- )
        {
           (evt->barcode_to_particle(ipp))->suggest_barcode( ipp+newlyGen );
        }
     }
     
     // now attach new generated photons to the vertex
     //
     for ( int ipnw=1; ipnw<=newlyGen; ipnw++ )
     {
         int nbcode = largestBarcode+ipnw;
         int pdg_id = HepMC::HEPEVT_Wrapper::id( nentries+ipnw );
         int status = HepMC::HEPEVT_Wrapper::status( nentries+ipnw );
         double px  =  HepMC::HEPEVT_Wrapper::px( nentries+ipnw );
         double py  =  HepMC::HEPEVT_Wrapper::py( nentries+ipnw );
         double pz  =  HepMC::HEPEVT_Wrapper::pz( nentries+ipnw );
         double e   =  HepMC::HEPEVT_Wrapper::e(  nentries+ipnw );
         double m   =  HepMC::HEPEVT_Wrapper::m(  nentries+ipnw );
      
         HepMC::GenParticle* NewPart = new HepMC::GenParticle( HepMC::FourVector(px,py,pz,e),
                                                                pdg_id, status);
         NewPart->set_generated_mass( m );
         NewPart->suggest_barcode( nbcode );
         vtx->add_particle_out( NewPart ) ;
         // add/shift scale factors towards the end of the list
         fScaleFactors.push_back( Scaling(HepMC::ThreeVector(1.,1.,1.),1) );
     }  
   } // end of if-statement 

   return;
}