/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_6_2_5/src/PhysicsTools/PatUtils/plugins/ShiftedPFCandidateProducerForNoPileUpPFMEt.cc

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#include "PhysicsTools/PatUtils/plugins/ShiftedPFCandidateProducerForNoPileUpPFMEt.h"

#include "JetMETCorrections/Objects/interface/JetCorrector.h"
#include "JetMETCorrections/Objects/interface/JetCorrectionsRecord.h"
#include "FWCore/Framework/interface/ESHandle.h"

#include "DataFormats/ParticleFlowCandidate/interface/PFCandidate.h"
#include "DataFormats/ParticleFlowCandidate/interface/PFCandidateFwd.h"
#include "DataFormats/JetReco/interface/PFJet.h"
#include "DataFormats/JetReco/interface/PFJetCollection.h"
#include "DataFormats/Common/interface/Handle.h"
#include "DataFormats/Math/interface/deltaR.h"

ShiftedPFCandidateProducerForNoPileUpPFMEt::ShiftedPFCandidateProducerForNoPileUpPFMEt(const edm::ParameterSet& cfg)
  : moduleLabel_(cfg.getParameter<std::string>("@module_label"))
{
  srcPFCandidates_ = cfg.getParameter<edm::InputTag>("srcPFCandidates");
  srcJets_ = cfg.getParameter<edm::InputTag>("srcJets");

  jetCorrUncertaintyTag_ = cfg.getParameter<std::string>("jetCorrUncertaintyTag");
  if ( cfg.exists("jetCorrInputFileName") ) {
    jetCorrInputFileName_ = cfg.getParameter<edm::FileInPath>("jetCorrInputFileName");
    if ( jetCorrInputFileName_.location() == edm::FileInPath::Unknown) throw cms::Exception("ShiftedJetProducerT") 
      << " Failed to find JEC parameter file = " << jetCorrInputFileName_ << " !!\n";
    std::cout << "Reading JEC parameters = " << jetCorrUncertaintyTag_  
              << " from file = " << jetCorrInputFileName_.fullPath() << "." << std::endl;
    jetCorrParameters_ = new JetCorrectorParameters(jetCorrInputFileName_.fullPath().data(), jetCorrUncertaintyTag_);
    jecUncertainty_ = new JetCorrectionUncertainty(*jetCorrParameters_);
  } else {
    std::cout << "Reading JEC parameters = " << jetCorrUncertaintyTag_
              << " from DB/SQLlite file." << std::endl;
    jetCorrPayloadName_ = cfg.getParameter<std::string>("jetCorrPayloadName");
  }

  minJetPt_ = cfg.getParameter<double>("minJetPt");

  shiftBy_ = cfg.getParameter<double>("shiftBy");
  
  unclEnUncertainty_ = cfg.getParameter<double>("unclEnUncertainty");

  produces<reco::PFCandidateCollection>();
}

ShiftedPFCandidateProducerForNoPileUpPFMEt::~ShiftedPFCandidateProducerForNoPileUpPFMEt()
{
// nothing to be done yet...
}

void ShiftedPFCandidateProducerForNoPileUpPFMEt::produce(edm::Event& evt, const edm::EventSetup& es)
{
  edm::Handle<reco::PFCandidateCollection> originalPFCandidates;
  evt.getByLabel(srcPFCandidates_, originalPFCandidates);

  edm::Handle<reco::PFJetCollection> jets;
  evt.getByLabel(srcJets_, jets);

  std::vector<const reco::PFJet*> selectedJets;
  for ( reco::PFJetCollection::const_iterator jet = jets->begin();
        jet != jets->end(); ++jet ) {
    if ( jet->pt() > minJetPt_ ) selectedJets.push_back(&(*jet));
  }

  if ( jetCorrPayloadName_ != "" ) {
      edm::ESHandle<JetCorrectorParametersCollection> jetCorrParameterSet;
      es.get<JetCorrectionsRecord>().get(jetCorrPayloadName_, jetCorrParameterSet); 
      const JetCorrectorParameters& jetCorrParameters = (*jetCorrParameterSet)[jetCorrUncertaintyTag_];
      delete jecUncertainty_;
      jecUncertainty_ = new JetCorrectionUncertainty(jetCorrParameters);
    }

  std::auto_ptr<reco::PFCandidateCollection> shiftedPFCandidates(new reco::PFCandidateCollection);

  for ( reco::PFCandidateCollection::const_iterator originalPFCandidate = originalPFCandidates->begin();
        originalPFCandidate != originalPFCandidates->end(); ++originalPFCandidate ) {
    
    const reco::PFJet* jet_matched = 0;
    for ( std::vector<const reco::PFJet*>::iterator jet = selectedJets.begin();
          jet != selectedJets.end(); ++jet ) {
      std::vector<reco::PFCandidatePtr> jetConstituents = (*jet)->getPFConstituents();
      for ( std::vector<reco::PFCandidatePtr>::const_iterator jetConstituent = jetConstituents.begin();
            jetConstituent != jetConstituents.end() && !jet_matched; ++jetConstituent ) {
        if ( deltaR(originalPFCandidate->p4(), (*jetConstituent)->p4()) < 1.e-2 ) jet_matched = (*jet);
      }
    }

    double shift = 0.;
    if ( jet_matched ) {
      jecUncertainty_->setJetEta(jet_matched->eta());
      jecUncertainty_->setJetPt(jet_matched->pt());
      
      shift = jecUncertainty_->getUncertainty(true);
    } else {
      shift = unclEnUncertainty_;
    }

    shift *= shiftBy_;
    
    reco::Candidate::LorentzVector shiftedPFCandidateP4 = originalPFCandidate->p4();
    shiftedPFCandidateP4 *= (1. + shift);
    
    reco::PFCandidate shiftedPFCandidate(*originalPFCandidate);      
    shiftedPFCandidate.setP4(shiftedPFCandidateP4);
    
    shiftedPFCandidates->push_back(shiftedPFCandidate);
  }
  
  evt.put(shiftedPFCandidates);
}

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

DEFINE_FWK_MODULE(ShiftedPFCandidateProducerForNoPileUpPFMEt);