adjustForPileup.cc

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#include "RecoJets/FFTJetAlgorithms/interface/adjustForPileup.h"

namespace fftjetcms {
  math::XYZTLorentzVector adjustForPileup(const math::XYZTLorentzVector& jet,
                                          const math::XYZTLorentzVector& pileup,
                                          const bool subtractPileupAs4Vec) {
    const double pt = jet.Pt();
    if (pt > 0.0) {
      const double pileupPt = pileup.Pt();
      const double ptFactor = (pt - pileupPt) / pt;
      if (ptFactor <= 0.0)
        return math::XYZTLorentzVector();
      else if (subtractPileupAs4Vec) {
        const math::XYZTLorentzVector subtracted(jet - pileup);
        const double e = subtracted.E();
        if (e <= 0.0)
          return math::XYZTLorentzVector();
        else {
          // Avoid negative jet masses
          const double px = subtracted.Px();
          const double py = subtracted.Py();
          const double pz = subtracted.Pz();
          if (e * e < px * px + py * py + pz * pz)
            // It is not clear what is the best thing to do here.
            // For now, revert to Pt scaling.
            return jet * ptFactor;
          else
            return subtracted;
        }
      } else
        return jet * ptFactor;
    } else
      return jet;
  }
}  // namespace fftjetcms