SubjetBuilder.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
#include "DiTauRec/SubjetBuilder.h"
 
// fastjet includes
#include "fastjet/ClusterSequenceArea.hh"
#include "fastjet/AreaDefinition.hh"
 
SubjetBuilder::SubjetBuilder(const std::string& type,
                 const std::string& name,
                 const IInterface * parent) :
  DiTauToolBase(type, name, parent)
{
  declareInterface<DiTauToolBase > (this);
}
 
 
SubjetBuilder::~SubjetBuilder() = default;
 
 
StatusCode SubjetBuilder::initialize() {
 
  return StatusCode::SUCCESS;
}
 
 
StatusCode SubjetBuilder::execute(DiTauCandidateData * data,
                                  const EventContext& /*ctx*/) const {
 
  ATH_MSG_DEBUG("subjet builder executing...");
 
  // get seed jet
  xAOD::DiTauJet* pDiTau = data->xAODDiTau;
 
  if (pDiTau == nullptr) {
    ATH_MSG_ERROR("no di-tau candidate given");
    return StatusCode::FAILURE;
  }
 
  const xAOD::Jet* pSeed = data->seed;
  if (!pSeed) {
    ATH_MSG_WARNING("no seed given. Di-Tau can not be reconstructed.");
    return StatusCode::FAILURE;
  }
 
  // retrieve seed jet clusters 
    
  using namespace fastjet;
  const xAOD::JetConstituentVector vConst = pSeed->getConstituents();
 
  if (vConst.empty()) {
    ATH_MSG_WARNING("cluster constituents could not be retrieved from seed jet");
    return StatusCode::FAILURE;
  }
 
  std::vector<PseudoJet> vpjClusters;
 
  for (const auto *cl: vConst) {
 
    TLorentzVector temp_p4;
    temp_p4.SetPtEtaPhiM(cl->pt(), cl->eta(), cl->phi(), cl->m());
    PseudoJet c( temp_p4.Px(), temp_p4.Py(), temp_p4.Pz(), temp_p4.E());
 
    vpjClusters.push_back(c);
  }
 
  // reconstruct subjets
 
  // Jet and area definitions
  JetDefinition jd = JetDefinition(antikt_algorithm, m_Rsubjet);
  AreaDefinition area_def(active_area_explicit_ghosts,GhostedAreaSpec(SelectorAbsRapMax(4.0)));
  ClusterSequenceArea cs(vpjClusters, jd, area_def); 
 
  // store (pt-sorted) subjets
  std::vector<PseudoJet> vSubjets = sorted_by_pt( cs.inclusive_jets(m_ptmin) );
  if (vSubjets.size()<=1) {
    ATH_MSG_DEBUG("Found less than 2 subjets. Reject ditau candidate");
    return StatusCode::FAILURE;
  }
 
  ATH_MSG_DEBUG("found "<< vSubjets.size() << " subjets");
  for (const auto& subjet: vSubjets) {
    ATH_MSG_DEBUG("pt: " << subjet.pt() << "  eta: " << subjet.eta() << "  phi: " << subjet.phi());
  }
 
  data->subjets = vSubjets;
  
  vSubjets.clear();
 
  return StatusCode::SUCCESS;
}