KtMassDrop.cxx

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/*
  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
*/
 
#include "JetSubStructureUtils/KtMassDrop.h"
#include "fastjet/ClusterSequence.hh"
#include "fastjet/JetDefinition.hh"
#include <math.h>
#include <float.h>
 
using namespace std;
using namespace JetSubStructureUtils;
 
double KtMassDrop::result(const fastjet::PseudoJet &jet) const
{
  if(jet.m() == 0 ) return -1;
  if(jet.constituents().empty()) return -1;
    
  fastjet::JetDefinition jet_def = fastjet::JetDefinition(fastjet::kt_algorithm, 1.5,
                                                          fastjet::E_scheme, fastjet::Best);
  fastjet::ClusterSequence kt_clust_seq(jet.constituents(), jet_def);
  fastjet::PseudoJet kt_jet = fastjet::sorted_by_pt(kt_clust_seq.inclusive_jets()).front();
 
  fastjet::PseudoJet p1, p2;
  if(kt_jet.has_parents(p1, p2)) {
    return fmax(p1.m(), p2.m()) / jet.m();
  }
 
  // No parents
  return -1;
}