/data/refman/pasoursint/CMSSW_5_3_0/src/RecoTauTag/RecoTau/plugins/PFRecoTauDiscriminationByDeltaE.cc

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#include "RecoTauTag/RecoTau/interface/TauDiscriminationProducerBase.h"
#include "FWCore/Utilities/interface/InputTag.h"

/* class PFRecoTauDiscriminationByDeltaE
 * created : August 30 2010,
 * contributors : Sami Lehti (sami.lehti@cern.ch ; HIP, Helsinki)
 * based on H+ tau ID by Lauri Wendland
 */

#include "TLorentzVector.h"

using namespace reco;
using namespace std;
using namespace edm;

class PFRecoTauDiscriminationByDeltaE : public PFTauDiscriminationProducerBase  {
    public:
        explicit PFRecoTauDiscriminationByDeltaE(const ParameterSet& iConfig):PFTauDiscriminationProducerBase(iConfig){
                deltaEmin               = iConfig.getParameter<double>("deltaEmin");
                deltaEmax               = iConfig.getParameter<double>("deltaEmax");
                chargedPionMass         = 0.139;
                booleanOutput           = iConfig.getParameter<bool>("BooleanOutput");
        }

        ~PFRecoTauDiscriminationByDeltaE(){}

        void beginEvent(const edm::Event&, const edm::EventSetup&);
        double discriminate(const reco::PFTauRef&);

    private:
        double DeltaE(const PFTauRef&);

        double chargedPionMass;

        double deltaEmin,deltaEmax;
        bool booleanOutput;
};

void PFRecoTauDiscriminationByDeltaE::beginEvent(const Event& iEvent, const EventSetup& iSetup){
}

double PFRecoTauDiscriminationByDeltaE::discriminate(const PFTauRef& tau){

        double dE = DeltaE(tau);
        if(booleanOutput) return ( dE > deltaEmin && dE < deltaEmax ? 1. : 0. );
        return dE;
}

double PFRecoTauDiscriminationByDeltaE::DeltaE(const PFTauRef& tau){
        double tracksE = 0;
        PFCandidateRefVector signalTracks = tau->signalPFChargedHadrCands();
        for(size_t i = 0; i < signalTracks.size(); ++i){
                TLorentzVector p4;
                p4.SetXYZM(signalTracks[i]->px(),
                           signalTracks[i]->py(),
                           signalTracks[i]->pz(),
                           chargedPionMass);
                tracksE += p4.E();
        }

        double hadrTauP = tau->momentum().r() * (1.0 - tau->emFraction());
        if (tau->emFraction() >= 1.0) {
                return -1.0; // electron
        } else {
                return tracksE / hadrTauP - 1.0;
        }
}

DEFINE_FWK_MODULE(PFRecoTauDiscriminationByDeltaE);