/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_6_2_5/src/TopQuarkAnalysis/TopJetCombination/plugins/TtSemiLepJetCombGeom.cc

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#include "TopQuarkAnalysis/TopJetCombination/plugins/TtSemiLepJetCombGeom.h"

#include "Math/VectorUtil.h"

#include "AnalysisDataFormats/TopObjects/interface/TtSemiLepEvtPartons.h"
#include "DataFormats/RecoCandidate/interface/RecoCandidate.h"
#include "FWCore/ParameterSet/interface/ParameterSet.h"

TtSemiLepJetCombGeom::TtSemiLepJetCombGeom(const edm::ParameterSet& cfg):
  jets_             (cfg.getParameter<edm::InputTag>("jets"             )),
  leps_             (cfg.getParameter<edm::InputTag>("leps"             )),
  maxNJets_         (cfg.getParameter<int>          ("maxNJets"         )),
  useDeltaR_        (cfg.getParameter<bool>         ("useDeltaR"        )),
  useBTagging_      (cfg.getParameter<bool>         ("useBTagging"      )),
  bTagAlgorithm_    (cfg.getParameter<std::string>  ("bTagAlgorithm"    )),
  minBDiscBJets_    (cfg.getParameter<double>       ("minBDiscBJets"    )),
  maxBDiscLightJets_(cfg.getParameter<double>       ("maxBDiscLightJets"))
{
  if(maxNJets_<4 && maxNJets_!=-1)
    throw cms::Exception("WrongConfig") 
      << "Parameter maxNJets can not be set to " << maxNJets_ << ". \n"
      << "It has to be larger than 4 or can be set to -1 to take all jets.";

  produces<std::vector<std::vector<int> > >();
  produces<int>("NumberOfConsideredJets");
}

TtSemiLepJetCombGeom::~TtSemiLepJetCombGeom()
{
}

void
TtSemiLepJetCombGeom::produce(edm::Event& evt, const edm::EventSetup& setup)
{
  std::auto_ptr<std::vector<std::vector<int> > > pOut(new std::vector<std::vector<int> >);
  std::auto_ptr<int> pJetsConsidered(new int);

  std::vector<int> match;
  for(unsigned int i = 0; i < 4; ++i) 
    match.push_back( -1 );

  // get jets
  edm::Handle< std::vector<pat::Jet> > jets;
  evt.getByLabel(jets_, jets);

  // get leptons
  edm::Handle< edm::View<reco::RecoCandidate> > leps; 
  evt.getByLabel(leps_, leps);

  // skip events without lepton candidate or less than 4 jets
  if(leps->empty() || jets->size() < 4){
    pOut->push_back( match );
    evt.put(pOut);
    *pJetsConsidered = jets->size();
    evt.put(pJetsConsidered, "NumberOfConsideredJets");
    return;
  }

  unsigned maxNJets = maxNJets_;
  if(maxNJets_ == -1 || (int)jets->size() < maxNJets_) maxNJets = jets->size();
  *pJetsConsidered = maxNJets;
  evt.put(pJetsConsidered, "NumberOfConsideredJets");

  std::vector<bool> isBJet;
  std::vector<bool> isLJet;
  int cntBJets = 0;
  if(useBTagging_) {
    for(unsigned int idx=0; idx<maxNJets; ++idx) {
      isBJet.push_back( ((*jets)[idx].bDiscriminator(bTagAlgorithm_) > minBDiscBJets_    ) );
      isLJet.push_back( ((*jets)[idx].bDiscriminator(bTagAlgorithm_) < maxBDiscLightJets_) );
      if((*jets)[idx].bDiscriminator(bTagAlgorithm_) > minBDiscBJets_    )cntBJets++;
    }
  }
  
  // -----------------------------------------------------
  // associate those two jets to the hadronic W boson that
  // have the smallest distance to each other
  // -----------------------------------------------------
  double minDist=-1.;
  int lightQ   =-1;
  int lightQBar=-1;
  for(unsigned int idx=0; idx<maxNJets; ++idx){
    if(useBTagging_ && (!isLJet[idx] || (cntBJets<=2 && isBJet[idx]))) continue;
    for(unsigned int jdx=(idx+1); jdx<maxNJets; ++jdx){
      if(useBTagging_ && (!isLJet[jdx] || (cntBJets<=2 && isBJet[jdx]) || (cntBJets==3 && isBJet[idx] && isBJet[jdx]))) continue;
      double dist = distance((*jets)[idx].p4(), (*jets)[jdx].p4());
      if( minDist<0. || dist<minDist ){
        minDist=dist;
        lightQ   =idx;
        lightQBar=jdx;
      }
    }
  }

  reco::Particle::LorentzVector wHad;
  if( isValid(lightQ, jets) && isValid(lightQBar, jets) )
    wHad = (*jets)[lightQ].p4() + (*jets)[lightQBar].p4();

  // -----------------------------------------------------
  // associate to the hadronic b quark the remaining jet
  // that has the smallest distance to the hadronic W 
  // -----------------------------------------------------
  minDist=-1.;
  int hadB=-1;
  if( isValid(lightQ, jets) && isValid(lightQBar, jets) ) {
    for(unsigned int idx=0; idx<maxNJets; ++idx){
      if(useBTagging_ && !isBJet[idx]) continue;
      // make sure it's not used up already from the hadronic W
      if( (int)idx!=lightQ && (int)idx!=lightQBar ) {
        double dist = distance((*jets)[idx].p4(), wHad);
        if( minDist<0. || dist<minDist ){
          minDist=dist;
          hadB=idx;
        }
      }
    }
  }

  // -----------------------------------------------------
  // associate to the leptonic b quark the remaining jet
  // that has the smallest distance to the leading lepton
  // -----------------------------------------------------
  minDist=-1.;
  int lepB=-1;
  for(unsigned int idx=0; idx<maxNJets; ++idx){
    if(useBTagging_ && !isBJet[idx]) continue;
    // make sure it's not used up already from the hadronic decay chain
    if( (int)idx!=lightQ && (int)idx!=lightQBar && (int)idx!=hadB ){
      double dist = distance((*jets)[idx].p4(), (*leps)[0].p4());
      if( minDist<0. || dist<minDist ){
        minDist=dist;
        lepB=idx;
      }
    }
  }

  match[TtSemiLepEvtPartons::LightQ   ] = lightQ;
  match[TtSemiLepEvtPartons::LightQBar] = lightQBar;
  match[TtSemiLepEvtPartons::HadB     ] = hadB;
  match[TtSemiLepEvtPartons::LepB     ] = lepB;

  pOut->push_back( match );
  evt.put(pOut);
}

double
TtSemiLepJetCombGeom::distance(const math::XYZTLorentzVector& v1, const math::XYZTLorentzVector& v2)
{
  // calculate the distance between two lorentz vectors 
  // using DeltaR or DeltaTheta
  if(useDeltaR_) return ROOT::Math::VectorUtil::DeltaR(v1, v2);
  return fabs(v1.theta() - v2.theta());
}