/data/refman/pasoursint/CMSSW_5_3_3/src/Calibration/Tools/plugins/ElectronSqPtTkIsolation.cc

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//C++ includes
#include <vector>
#include <functional>

//ROOT includes
#include <Math/VectorUtil.h>

//CMSSW includes
#include "Calibration/Tools/plugins/ElectronSqPtTkIsolation.h"
#include "DataFormats/TrackReco/interface/TrackFwd.h"
#include "TrackingTools/PatternTools/interface/Trajectory.h"
#include "TrackingTools/TrajectoryState/interface/TrajectoryStateTransform.h"
#include "DataFormats/GeometryVector/interface/GlobalPoint.h"
#include "DataFormats/GeometryVector/interface/GlobalVector.h"
#include "DataFormats/GsfTrackReco/interface/GsfTrack.h"

using namespace ROOT::Math::VectorUtil ;


ElectronSqPtTkIsolation::ElectronSqPtTkIsolation (double extRadius,
                          double intRadius,
                          double ptLow,
                          double lip,
                          const reco::TrackCollection* trackCollection)   :
  extRadius_(extRadius),
  intRadius_(intRadius),
  ptLow_(ptLow),
  lip_(lip),
  trackCollection_(trackCollection)  
{
}

ElectronSqPtTkIsolation::~ElectronSqPtTkIsolation ()
{
}

// unified acces to isolations
std::pair<int,double> ElectronSqPtTkIsolation::getIso(const reco::GsfElectron* electron) const  
{
  int counter  =0 ;
  double ptSum =0.;
  //Take the electron track
  reco::GsfTrackRef tmpTrack = electron->gsfTrack() ;
  math::XYZVector tmpElectronMomentumAtVtx = (*tmpTrack).momentum () ; 

  for ( reco::TrackCollection::const_iterator itrTr  = (*trackCollection_).begin() ; 
                                              itrTr != (*trackCollection_).end()   ; 
                                              ++itrTr ) 
    {
        math::XYZVector tmpTrackMomentumAtVtx = (*itrTr).momentum () ; 
        double this_pt  = (*itrTr).pt();
        if ( this_pt < ptLow_ ) 
          continue ;  
        if (fabs( (*itrTr).dz() - (*tmpTrack).dz() ) > lip_ )
          continue ;
        double dr = DeltaR(tmpTrackMomentumAtVtx,tmpElectronMomentumAtVtx) ;
        if ( fabs(dr) < extRadius_ && 
             fabs(dr) >= intRadius_ )
          {
            ++counter ;
            ptSum += this_pt*this_pt;    // sum of squared pT
          }
    }//end loop over tracks                 

  std::pair<int,double> retval;
  retval.first  = counter;
  retval.second = ptSum;

  return retval;
}


int ElectronSqPtTkIsolation::getNumberTracks (const reco::GsfElectron* electron) const
{  
  //counter for the tracks in the isolation cone
  return getIso(electron).first ;
}

double ElectronSqPtTkIsolation::getPtTracks (const reco::GsfElectron* electron) const
{
  return getIso(electron).second ;
}