GhostTrackComputer.cc

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#include <iostream>
#include <cstddef>
#include <string>
#include <cmath>
#include <vector>

#include <Math/VectorUtil.h>

#include "FWCore/Utilities/interface/Exception.h"
#include "FWCore/ParameterSet/interface/ParameterSet.h"

#include "DataFormats/Math/interface/Vector3D.h"
#include "DataFormats/Math/interface/LorentzVector.h"
#include "DataFormats/GeometryCommonDetAlgo/interface/Measurement1D.h"
#include "DataFormats/GeometryVector/interface/GlobalPoint.h"
#include "DataFormats/GeometryVector/interface/GlobalVector.h"
#include "DataFormats/GeometryVector/interface/VectorUtil.h"
#include "DataFormats/TrackReco/interface/Track.h"
#include "DataFormats/TrackReco/interface/TrackFwd.h"
#include "DataFormats/BTauReco/interface/TrackIPTagInfo.h"
#include "DataFormats/BTauReco/interface/SecondaryVertexTagInfo.h"  
#include "DataFormats/BTauReco/interface/TaggingVariable.h"
#include "DataFormats/BTauReco/interface/VertexTypes.h"

#include "RecoBTag/SecondaryVertex/interface/ParticleMasses.h"
#include "RecoBTag/SecondaryVertex/interface/TrackSorting.h"
#include "RecoBTag/SecondaryVertex/interface/TrackSelector.h"
#include "RecoBTag/SecondaryVertex/interface/TrackKinematics.h"
#include "RecoBTag/SecondaryVertex/interface/V0Filter.h"

#include "RecoBTag/SecondaryVertex/interface/GhostTrackComputer.h"

using namespace reco;

static edm::ParameterSet dropDeltaR(const edm::ParameterSet &pset)
{
    edm::ParameterSet psetCopy(pset);
    psetCopy.addParameter<double>("jetDeltaRMax", 99999.0);
    return psetCopy;
}

GhostTrackComputer::GhostTrackComputer(const edm::ParameterSet &params) :
    charmCut(params.getParameter<double>("charmCut")),
    sortCriterium(TrackSorting::getCriterium(params.getParameter<std::string>("trackSort"))),
    trackSelector(params.getParameter<edm::ParameterSet>("trackSelection")),
    trackNoDeltaRSelector(dropDeltaR(params.getParameter<edm::ParameterSet>("trackSelection"))),
    minTrackWeight(params.getParameter<double>("minimumTrackWeight")),
    trackPairV0Filter(params.getParameter<edm::ParameterSet>("trackPairV0Filter"))
{
}

const TrackIPTagInfo::TrackIPData &
GhostTrackComputer::threshTrack(const TrackIPTagInfo &trackIPTagInfo,
                                const TrackIPTagInfo::SortCriteria sort,
                                const reco::Jet &jet,
                                const GlobalPoint &pv) const
{
    const edm::RefVector<TrackCollection> &tracks =
                    trackIPTagInfo.selectedTracks();
    const std::vector<TrackIPTagInfo::TrackIPData> &ipData =
                    trackIPTagInfo.impactParameterData();
    std::vector<std::size_t> indices = trackIPTagInfo.sortedIndexes(sort);

    TrackKinematics kin;
    for(std::vector<std::size_t>::const_iterator iter = indices.begin();
        iter != indices.end(); ++iter) {
        const TrackIPTagInfo::TrackIPData &data = ipData[*iter];
        const Track &track = *tracks[*iter];

        if (!trackNoDeltaRSelector(track, data, jet, pv))
            continue;

        kin.add(track);
        if (kin.vectorSum().M() > charmCut) 
            return data;
    }

    static const TrackIPTagInfo::TrackIPData dummy = {
        GlobalPoint(),
        GlobalPoint(),
        Measurement1D(-1.0, 1.0),
        Measurement1D(-1.0, 1.0),
        Measurement1D(-1.0, 1.0),
        Measurement1D(-1.0, 1.0),
        0.
    };
    return dummy;
}

static double etaRel(const math::XYZVector &dir, const math::XYZVector &track)
{
    double momPar = dir.Dot(track);
    double energy = std::sqrt(track.Mag2() +
                              ROOT::Math::Square(ParticleMasses::piPlus));

    return 0.5 * std::log((energy + momPar) / (energy - momPar));
}

static void addMeas(std::pair<double, double> &sum, Measurement1D meas)
{
    double weight = 1. / meas.error();
    weight *= weight;
    sum.first += weight * meas.value();
    sum.second += weight;
}

TaggingVariableList
GhostTrackComputer::operator () (const TrackIPTagInfo &ipInfo,
                                 const SecondaryVertexTagInfo &svInfo) const
{
    using namespace ROOT::Math;

    edm::RefToBase<Jet> jet = ipInfo.jet();
    math::XYZVector jetDir = jet->momentum().Unit();
    bool havePv = ipInfo.primaryVertex().isNonnull();
    GlobalPoint pv;
    if (havePv)
        pv = GlobalPoint(ipInfo.primaryVertex()->x(),
                         ipInfo.primaryVertex()->y(),
                         ipInfo.primaryVertex()->z());

    btag::Vertices::VertexType vtxType = btag::Vertices::NoVertex;

    TaggingVariableList vars;

    vars.insert(btau::jetPt, jet->pt(), true);
    vars.insert(btau::jetEta, jet->eta(), true);

    TrackKinematics allKinematics;
    TrackKinematics vertexKinematics;
    TrackKinematics trackKinematics;

    std::pair<double, double> vertexDist2D, vertexDist3D;
    std::pair<double, double> tracksDist2D, tracksDist3D;

    unsigned int nVertices = 0;
    unsigned int nVertexTracks = 0;
    unsigned int nTracks = 0;
    for(unsigned int i = 0; i < svInfo.nVertices(); i++) {
        const Vertex &vertex = svInfo.secondaryVertex(i);
        bool hasRefittedTracks = vertex.hasRefittedTracks();
        TrackRefVector tracks = svInfo.vertexTracks(i);
        unsigned int n = 0;
        for(TrackRefVector::const_iterator track = tracks.begin();
            track != tracks.end(); track++)
            if (svInfo.trackWeight(i, *track) >= minTrackWeight)
                n++;

        if (n < 1)
            continue;
        bool isTrackVertex = (n == 1);
        ++*(isTrackVertex ? &nTracks : &nVertices);

        addMeas(*(isTrackVertex ? &tracksDist2D : &vertexDist2D),
                    svInfo.flightDistance(i, true));
        addMeas(*(isTrackVertex ? &tracksDist3D : &vertexDist3D),
                    svInfo.flightDistance(i, false));

        TrackKinematics &kin = isTrackVertex ? trackKinematics
                                             : vertexKinematics;
        for(TrackRefVector::const_iterator track = tracks.begin();
            track != tracks.end(); track++) {
            float w = svInfo.trackWeight(i, *track);
            if (w < minTrackWeight)
                continue;
            if (hasRefittedTracks) {
                Track actualTrack =
                        vertex.refittedTrack(*track);
                kin.add(actualTrack, w);
                vars.insert(btau::trackEtaRel, etaRel(jetDir,
                        actualTrack.momentum()), true);
            } else {
                kin.add(**track, w);
                vars.insert(btau::trackEtaRel, etaRel(jetDir,
                        (*track)->momentum()), true);
            }
            if (!isTrackVertex)
                nVertexTracks++;
        }
    }

    Measurement1D dist2D, dist3D;
    if (nVertices) {
        vtxType = btag::Vertices::RecoVertex;

        if (nVertices == 1 && nTracks) {
            vertexDist2D.first += tracksDist2D.first;
            vertexDist2D.second += tracksDist2D.second;
            vertexDist3D.first += tracksDist3D.first;
            vertexDist3D.second += tracksDist3D.second;
            vertexKinematics += trackKinematics;
        }

        dist2D = Measurement1D(
                vertexDist2D.first / vertexDist2D.second,
                std::sqrt(1. / vertexDist2D.second));
        dist3D = Measurement1D(
                vertexDist3D.first / vertexDist3D.second,
                std::sqrt(1. / vertexDist3D.second));

        vars.insert(btau::jetNSecondaryVertices, nVertices, true);
        vars.insert(btau::vertexNTracks, nVertexTracks, true);
    } else if (nTracks) {
        vtxType = btag::Vertices::PseudoVertex;
        vertexKinematics = trackKinematics;

        dist2D = Measurement1D(
                tracksDist2D.first / tracksDist2D.second,
                std::sqrt(1. / tracksDist2D.second));
        dist3D = Measurement1D(
                tracksDist3D.first / tracksDist3D.second,
                std::sqrt(1. / tracksDist3D.second));
    }

    if (nVertices || nTracks) {
        vars.insert(btau::flightDistance2dVal, dist2D.value(), true);
        vars.insert(btau::flightDistance2dSig, dist2D.significance(), true);
        vars.insert(btau::flightDistance3dVal, dist3D.value(), true);
        vars.insert(btau::flightDistance3dSig, dist3D.significance(), true);
        vars.insert(btau::vertexJetDeltaR,
                    Geom::deltaR(svInfo.flightDirection(0), jetDir),true);
        vars.insert(btau::jetNSingleTrackVertices, nTracks, true);
    }

    std::vector<std::size_t> indices = ipInfo.sortedIndexes(sortCriterium);
    const std::vector<TrackIPTagInfo::TrackIPData> &ipData =
                        ipInfo.impactParameterData();
    const edm::RefVector<TrackCollection> &tracks =
                        ipInfo.selectedTracks();

    TrackRef trackPairV0Test[2];
    for(unsigned int i = 0; i < indices.size(); i++) {
        std::size_t idx = indices[i];
        const TrackIPTagInfo::TrackIPData &data = ipData[idx];
        const TrackRef &trackRef = tracks[idx];
        const Track &track = *trackRef;

        // filter track

        if (!trackSelector(track, data, *jet, pv))
            continue;

        // add track to kinematics for all tracks in jet

        allKinematics.add(track);

        // check against all other tracks for V0 track pairs

        trackPairV0Test[0] = tracks[idx];
        bool ok = true;
        for(unsigned int j = 0; j < indices.size(); j++) {
            if (i == j)
                continue;

            std::size_t pairIdx = indices[j];
            const TrackIPTagInfo::TrackIPData &pairTrackData =
                            ipData[pairIdx];
            const TrackRef &pairTrackRef = tracks[pairIdx];
            const Track &pairTrack = *pairTrackRef;

            if (!trackSelector(pairTrack, pairTrackData, *jet, pv))
                continue;

            trackPairV0Test[1] = pairTrackRef;
            if (!trackPairV0Filter(trackPairV0Test, 2)) {
                ok = false;
                break;
            }
        }
        if (!ok)
            continue;

        // add track variables

        math::XYZVector trackMom = track.momentum();
        double trackMag = std::sqrt(trackMom.Mag2());

        vars.insert(btau::trackSip3dVal, data.ip3d.value(), true);
        vars.insert(btau::trackSip3dSig, data.ip3d.significance(), true);
        vars.insert(btau::trackSip2dVal, data.ip2d.value(), true);
        vars.insert(btau::trackSip2dSig, data.ip2d.significance(), true);
        vars.insert(btau::trackJetDistVal, data.distanceToJetAxis.value(), true);
        vars.insert(btau::trackGhostTrackDistVal, data.distanceToGhostTrack.value(), true);
        vars.insert(btau::trackGhostTrackDistSig, data.distanceToGhostTrack.significance(), true);
        vars.insert(btau::trackGhostTrackWeight, data.ghostTrackWeight, true);
        vars.insert(btau::trackDecayLenVal, havePv ? (data.closestToGhostTrack - pv).mag() : -1.0, true);

        vars.insert(btau::trackMomentum, trackMag, true);
        vars.insert(btau::trackEta, trackMom.Eta(), true);

        vars.insert(btau::trackChi2, track.normalizedChi2(), true);
        vars.insert(btau::trackNPixelHits, track.hitPattern().pixelLayersWithMeasurement(), true);
        vars.insert(btau::trackNTotalHits, track.hitPattern().trackerLayersWithMeasurement(), true);
        vars.insert(btau::trackPtRel, VectorUtil::Perp(trackMom, jetDir), true);
        vars.insert(btau::trackDeltaR, VectorUtil::DeltaR(trackMom, jetDir), true);
    } 

    vars.insert(btau::vertexCategory, vtxType, true);
    vars.insert(btau::trackSumJetDeltaR,
                VectorUtil::DeltaR(allKinematics.vectorSum(), jetDir), true);
    vars.insert(btau::trackSumJetEtRatio,
                allKinematics.vectorSum().Et() / ipInfo.jet()->et(), true);
    vars.insert(btau::trackSip3dSigAboveCharm,
                threshTrack(ipInfo, TrackIPTagInfo::IP3DSig, *jet, pv)
                                    .ip3d.significance(),
                true);
    vars.insert(btau::trackSip2dSigAboveCharm,
                threshTrack(ipInfo, TrackIPTagInfo::IP2DSig, *jet, pv)
                                    .ip2d.significance(),
                true);

    if (vtxType != btag::Vertices::NoVertex) {
        math::XYZTLorentzVector allSum = allKinematics.vectorSum();
        math::XYZTLorentzVector vertexSum = vertexKinematics.vectorSum();

        vars.insert(btau::vertexMass, vertexSum.M(), true);
        if (allKinematics.numberOfTracks())
            vars.insert(btau::vertexEnergyRatio,
                        vertexSum.E() / allSum.E(), true);
        else
            vars.insert(btau::vertexEnergyRatio, 1, true);
    }

    vars.finalize();

    return vars;
}