PFMETAlgo.cc

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#include "CommonTools/ParticleFlow/interface/PFMETAlgo.h"

#include "DataFormats/ParticleFlowCandidate/interface/PFCandidate.h"

#include "DataFormats/METReco/interface/MET.h"
#include "DataFormats/METReco/interface/METFwd.h"
#include "DataFormats/Math/interface/LorentzVector.h"

#include "FWCore/Framework/interface/EventSetup.h"

using namespace std;
using namespace edm;
using namespace reco;
using namespace math;
using namespace pf2pat;

PFMETAlgo::PFMETAlgo(const edm::ParameterSet& iConfig) {
  verbose_ = iConfig.getUntrackedParameter<bool>("verbose", false);

  hfCalibFactor_ = iConfig.getParameter<double>("hfCalibFactor");
}

reco::MET PFMETAlgo::produce(const reco::PFCandidateCollection& pfCandidates) const {
  double sumEx = 0;
  double sumEy = 0;
  double sumEt = 0;

  for (unsigned i = 0; i < pfCandidates.size(); i++) {
    const reco::PFCandidate& cand = pfCandidates[i];

    double E = cand.energy();

    if (cand.particleId() == PFCandidate::h_HF || cand.particleId() == PFCandidate::egamma_HF)
      E *= hfCalibFactor_;

    double phi = cand.phi();
    double cosphi = cos(phi);
    double sinphi = sin(phi);

    double theta = cand.theta();
    double sintheta = sin(theta);

    double et = E * sintheta;
    double ex = et * cosphi;
    double ey = et * sinphi;

    sumEx += ex;
    sumEy += ey;
    sumEt += et;
  }

  double Et = sqrt(sumEx * sumEx + sumEy * sumEy);
  XYZTLorentzVector missingEt(-sumEx, -sumEy, 0, Et);

  if (verbose_) {
    cout << "PFMETAlgo: mEx, mEy, mEt = " << missingEt.X() << ", " << missingEt.Y() << ", " << missingEt.T() << endl;
  }

  XYZPoint vertex;  // dummy vertex
  return MET(sumEt, missingEt, vertex);
}