MiniIsolation.cc

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#include "DataFormats/Candidate/interface/Candidate.h"
#include "DataFormats/PatCandidates/interface/PackedCandidate.h"
#include "DataFormats/Math/interface/deltaR.h"
#include "PhysicsTools/PatUtils/interface/MiniIsolation.h"

namespace pat {

  // Computes MiniIsolation given a 4-vector of the object in question
  // and a collection of packed PF cands. Computed as a sum of PFCand pT
  // inside a cone of radius dR = max(mindir, min(maxdr, kt_scale/pT))
  // Excludes PFCands inside of "deadcone" radius.
  // For nh, ph, pu, only include particles with pT > ptthresh
  // Some documentation can be found here: https://hypernews.cern.ch/HyperNews/CMS/get/susy/1991.html

  float miniIsoDr(const reco::Candidate::PolarLorentzVector &p4, float mindr, float maxdr, float kt_scale) {
    return std::max(mindr, std::min(maxdr, float(kt_scale / p4.pt())));
  }

  PFIsolation getMiniPFIsolation(const pat::PackedCandidateCollection *pfcands,
                                 const reco::Candidate::PolarLorentzVector &p4,
                                 float mindr,
                                 float maxdr,
                                 float kt_scale,
                                 float ptthresh,
                                 float deadcone_ch,
                                 float deadcone_pu,
                                 float deadcone_ph,
                                 float deadcone_nh,
                                 float dZ_cut) {
    float chiso = 0, nhiso = 0, phiso = 0, puiso = 0;
    float drcut = miniIsoDr(p4, mindr, maxdr, kt_scale);
    for (auto const &pc : *pfcands) {
      float dr2 = deltaR2(p4, pc);
      if (dr2 > drcut * drcut)
        continue;
      float pt = pc.p4().pt();
      int id = pc.pdgId();
      if (std::abs(id) == 211) {
        bool fromPV = (pc.fromPV() > 1 || fabs(pc.dz()) < dZ_cut);
        if (fromPV && dr2 > deadcone_ch * deadcone_ch) {
          // if charged hadron and from primary vertex, add to charged hadron isolation
          chiso += pt;
        } else if (!fromPV && pt > ptthresh && dr2 > deadcone_pu * deadcone_pu) {
          // if charged hadron and NOT from primary vertex, add to pileup isolation
          puiso += pt;
        }
      }
      // if neutral hadron, add to neutral hadron isolation
      if (std::abs(id) == 130 && pt > ptthresh && dr2 > deadcone_nh * deadcone_nh)
        nhiso += pt;
      // if photon, add to photon isolation
      if (std::abs(id) == 22 && pt > ptthresh && dr2 > deadcone_ph * deadcone_ph)
        phiso += pt;
    }

    return pat::PFIsolation(chiso, nhiso, phiso, puiso);
  }

  double muonRelMiniIsoPUCorrected(const PFIsolation &iso,
                                   const reco::Candidate::PolarLorentzVector &p4,
                                   double dr,
                                   double rho,
                                   const std::vector<double> &area) {
    double absEta = std::abs(p4.eta());
    double ea = 0;
    //Eta dependent effective area
    if (absEta < 0.800)
      ea = area.at(0);
    else if (absEta < 1.300)
      ea = area.at(1);
    else if (absEta < 2.000)
      ea = area.at(2);
    else if (absEta < 2.200)
      ea = area.at(3);
    else if (absEta < 2.500)
      ea = area.at(4);

    double correction = rho * ea * (dr / 0.3) * (dr / 0.3);
    double correctedIso = iso.chargedHadronIso() + std::max(0.0, iso.neutralHadronIso() + iso.photonIso() - correction);
    return correctedIso / p4.pt();
  }

}  // namespace pat