/data/refman/pasoursint/CMSSW_5_3_1/src/RecoBTag/SecondaryVertex/src/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;
}