PATJetCorrExtractor.h

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#ifndef PhysicsTools_PatUtils_PATJetCorrExtractor_h
#define PhysicsTools_PatUtils_PATJetCorrExtractor_h

#include "FWCore/Framework/interface/Event.h"
#include "FWCore/Framework/interface/EventSetup.h"
#include "FWCore/Utilities/interface/Exception.h"

#include "JetMETCorrections/Type1MET/interface/JetCorrExtractorT.h"

#include "DataFormats/Common/interface/RefToBase.h"
#include "DataFormats/JetReco/interface/Jet.h"
#include "DataFormats/PatCandidates/interface/Jet.h"
#include "DataFormats/Candidate/interface/Candidate.h"

#include <string>
#include <vector>

namespace
{
  std::string format_vstring(const std::vector<std::string>& v)
  {
    std::string retVal;

    retVal.append("{ ");

    unsigned numEntries = v.size();
    for ( unsigned iEntry = 0; iEntry < numEntries; ++iEntry ) {
      retVal.append(v[iEntry]);
      if ( iEntry < (numEntries - 1) ) retVal.append(", ");
    }

    retVal.append(" }");

    return retVal;
  }
}

class PATJetCorrExtractor
{
 public:

  reco::Candidate::LorentzVector operator()(const pat::Jet rawJet, const reco::JetCorrector* jetCorr,
                        double jetCorrEtaMax = 9.9,
                        const reco::Candidate::LorentzVector * const rawJetP4_specified = nullptr) const
  {
     JetCorrExtractorT<pat::Jet> jetCorrExtractor;
     return jetCorrExtractor(rawJet, jetCorr, jetCorrEtaMax, rawJetP4_specified);
  }

  reco::Candidate::LorentzVector operator()(const pat::Jet& jet, const std::string& jetCorrLabel,
                        double jetCorrEtaMax = 9.9,
                        const reco::Candidate::LorentzVector* const rawJetP4_specified = nullptr) const
  {
    reco::Candidate::LorentzVector corrJetP4;

    try {
      corrJetP4 = jet.correctedP4(jetCorrLabel);
      if(rawJetP4_specified != nullptr) {
    //MM: compensate for potential removal of constituents (as muons)
    //similar effect in JetMETCorrection/Type1MET/interface/JetCorrExtractor.h
    reco::Candidate::LorentzVector rawJetP4 = jet.correctedP4("Uncorrected");
    double corrFactor = corrJetP4.pt()/rawJetP4.pt();
    corrJetP4 = (*rawJetP4_specified);
    corrJetP4 *= corrFactor;
    if(corrFactor<0) {
      edm::LogWarning("PATJetCorrExtractor") << "Negative jet energy scale correction noticed" << ".\n";
    }
      }
    } catch( cms::Exception const& ) {
      throw cms::Exception("InvalidRequest")
    << "The JEC level " << jetCorrLabel << " does not exist !!\n"
    << "Available levels = " << format_vstring(jet.availableJECLevels()) << ".\n";
    }

    return corrJetP4;
  }
};

#endif