/data/refman/pasoursint/CMSSW_5_3_3/src/RecoTauTag/RecoTau/src/PFTauDecayModeTools.cc

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#include <map>
#include <boost/assign.hpp>
#include "RecoTauTag/RecoTau/interface/PFTauDecayModeTools.h"
#include "DataFormats/JetReco/interface/GenJet.h"
#include "PhysicsTools/JetMCUtils/interface/JetMCTag.h"

namespace reco { namespace tau {

namespace {
  // Convert the string decay mode from PhysicsTools to the
  // PFTau::hadronicDecayMode format
  static std::map<std::string, reco::PFTau::hadronicDecayMode> dmTranslator =
    boost::assign::map_list_of
    ("oneProng0Pi0", reco::PFTau::kOneProng0PiZero)
    ("oneProng1Pi0", reco::PFTau::kOneProng1PiZero)
    ("oneProng2Pi0", reco::PFTau::kOneProng2PiZero)
    ("oneProngOther", reco::PFTau::kOneProngNPiZero)
    ("threeProng0Pi0", reco::PFTau::kThreeProng0PiZero)
    ("threeProng1Pi0", reco::PFTau::kThreeProng1PiZero)
    ("threeProngOther", reco::PFTau::kThreeProngNPiZero)
    ("electron", reco::PFTau::kNull)
    ("muon", reco::PFTau::kNull);

  static std::map<reco::PFTau::hadronicDecayMode, std::string> dmInverter =
    boost::assign::map_list_of
    (reco::PFTau::kOneProng0PiZero, "oneProng0Pi0")
    (reco::PFTau::kOneProng1PiZero, "oneProng1Pi0")
    (reco::PFTau::kOneProng2PiZero, "oneProng2Pi0")
    (reco::PFTau::kOneProngNPiZero, "oneProngOther")
    (reco::PFTau::kThreeProng0PiZero, "threeProng0Pi0")
    (reco::PFTau::kThreeProng1PiZero, "threeProng1Pi0")
    (reco::PFTau::kThreeProngNPiZero, "threeProngOther")
    (reco::PFTau::kNull, "unknown")
    (reco::PFTau::kRareDecayMode, "rare");
}

unsigned int chargedHadronsInDecayMode(PFTau::hadronicDecayMode mode) {
   int modeAsInt = static_cast<int>(mode);
   return (modeAsInt / PFTau::kOneProngNPiZero) + 1;
}

unsigned int piZerosInDecayMode(PFTau::hadronicDecayMode mode) {
   int modeAsInt = static_cast<int>(mode);
   return (modeAsInt % PFTau::kOneProngNPiZero);
}

PFTau::hadronicDecayMode translateDecayMode(
    unsigned int nCharged, unsigned int nPiZeros) {
   // If no tracks exist, this is definitely not a tau!
   if(!nCharged) return PFTau::kNull;
   // Find the maximum number of PiZeros our parameterization can hold
   const unsigned int maxPiZeros = PFTau::kOneProngNPiZero;
   // Determine our track index
   unsigned int trackIndex = (nCharged-1)*(maxPiZeros+1);
   // Check if we handle the given number of tracks
   if(trackIndex >= PFTau::kRareDecayMode) return PFTau::kRareDecayMode;

   nPiZeros = (nPiZeros <= maxPiZeros) ? nPiZeros : maxPiZeros;
   return static_cast<PFTau::hadronicDecayMode>(trackIndex + nPiZeros);
}

PFTau::hadronicDecayMode translateGenDecayModeToReco(
    const std::string& name) {
  std::map<std::string, reco::PFTau::hadronicDecayMode>::const_iterator
    found = dmTranslator.find(name);
  if (found != dmTranslator.end()) {
    return found->second;
  } else
    return reco::PFTau::kRareDecayMode;
}

std::string translateRecoDecayModeToGen(PFTau::hadronicDecayMode decayMode) {
  std::map<reco::PFTau::hadronicDecayMode, std::string>::const_iterator
    found = dmInverter.find(decayMode);
  if (found != dmInverter.end()) {
    return found->second;
  } else
    return "unknown";
}


PFTau::hadronicDecayMode getDecayMode(const reco::GenJet* genJet) {
  if (!genJet)
    return reco::PFTau::kNull;
  return translateGenDecayModeToReco(JetMCTagUtils::genTauDecayMode(*genJet));
}

}} // end namespace reco::tau