PFDisplacedVertexHelper Class Reference

Displaced Vertex Finder Algorithm. More...

#include <PFDisplacedVertexHelper.h>

Classes
struct	TracksSelector
	Tool which store the information for the tracks selection. More...
struct	VertexIdentifier
	Tool which store the information for the vertex identification. More...

Public Member Functions
void	Dump (std::ostream &out=std::cout) const
reco::PFDisplacedVertex::VertexType	identifyVertex (const reco::PFDisplacedVertex &v) const
	Vertex identification tool. More...
bool	isTrackSelected (const reco::Track &trk, const reco::PFDisplacedVertex::VertexTrackType vertexTrackType) const
	Select tracks tool. More...
	PFDisplacedVertexHelper ()
math::XYZPoint	primaryVertex () const
	Set Vertex direction using the primary vertex. More...
void	setPrimaryVertex (edm::Handle< reco::VertexCollection > mainVertexHandle, edm::Handle< reco::BeamSpot > beamSpotHandle)
	Update the primary vertex information. More...
void	setTracksSelector (const edm::ParameterSet &ps)
	Set Tracks selector parameters. More...
void	setVertexIdentifier (const edm::ParameterSet &ps)
	Set Vertex identifier parameters. More...
	~PFDisplacedVertexHelper ()

Private Member Functions
bool	isKaonMass (const reco::PFDisplacedVertex &v) const
int	lambdaCP (const reco::PFDisplacedVertex &v) const
	Tools used to calculate quantities for vertex identification. More...

Private Attributes
math::XYZPoint	pvtx_
	Primary vertex information updated for each event. More...
TracksSelector	tracksSelector_
VertexIdentifier	vertexIdentifier_

Static Private Attributes
static const double	muon_mass2 = 0.106 * 0.106
static const double	pion_mass2 = 0.0194
	Masses2 taken from PDG. More...
static const double	proton_mass2 = 0.938 * 0.938

Detailed Description

Displaced Vertex Finder Algorithm.

Author

Maxime Gouzevitch

Date

October 2009

Definition at line 17 of file PFDisplacedVertexHelper.h.

Constructor & Destructor Documentation

PFDisplacedVertexHelper()

PFDisplacedVertexHelper::PFDisplacedVertexHelper

(

)

Definition at line 18 of file PFDisplacedVertexHelper.cc.

    : tracksSelector_(), vertexIdentifier_(), pvtx_(math::XYZPoint(0, 0, 0)) {}

~PFDisplacedVertexHelper()

PFDisplacedVertexHelper::~PFDisplacedVertexHelper

(

)

Definition at line 21 of file PFDisplacedVertexHelper.cc.

{}

Member Function Documentation

Dump()

void PFDisplacedVertexHelper::Dump

(

std::ostream &

out = std::cout

)

const

Definition at line 307 of file PFDisplacedVertexHelper.cc.

                                                        {
  tracksSelector_.Dump();
  vertexIdentifier_.Dump();
  out << " pvtx_ = " << pvtx_ << std::endl;
}

References PFDisplacedVertexHelper::TracksSelector::Dump(), PFDisplacedVertexHelper::VertexIdentifier::Dump(), MillePedeFileConverter_cfg::out, pvtx_, tracksSelector_, and vertexIdentifier_.

identifyVertex()

reco::PFDisplacedVertex::VertexType PFDisplacedVertexHelper::identifyVertex

(

const reco::PFDisplacedVertex &

v

)

const

Vertex identification tool.

Definition at line 72 of file PFDisplacedVertexHelper.cc.

                                                                                                            {
  if (!vertexIdentifier_.identifyVertices())
    return PFDisplacedVertex::ANY;
 
  PFDisplacedVertex::M_Hypo massElec = PFDisplacedVertex::M_MASSLESS;
  PFDisplacedVertex::M_Hypo massPion = PFDisplacedVertex::M_PION;
 
  math::XYZTLorentzVector mom_ee = v.secondaryMomentum(massElec, true);
  math::XYZTLorentzVector mom_pipi = v.secondaryMomentum(massPion, true);
 
  // ===== (1) Identify fake and looper vertices ===== //
 
  double ang = v.angle_io();
  double pt_ee = mom_ee.Pt();
  double eta_vtx = v.position().eta();
 
  //cout << "Angle = " << ang << endl;
 
  bool bDirectionFake = ang > vertexIdentifier_.angle_max();
  bool bLowPt = pt_ee < vertexIdentifier_.pt_min();
  bool bLooperEta = fabs(eta_vtx) < vertexIdentifier_.looper_eta_max();
 
  bool isFake = bDirectionFake || (bLowPt && !bLooperEta);
  bool isLooper = !bDirectionFake && bLowPt && bLooperEta;
 
  if (isFake)
    return PFDisplacedVertex::FAKE;
  if (isLooper)
    return PFDisplacedVertex::LOOPER;
 
  // ===== (2) Identify Decays and Conversions ===== //
 
  int c1 = v.originalTrack(v.refittedTracks()[0])->charge();
  int c2 = v.originalTrack(v.refittedTracks()[1])->charge();
  double mass_ee = mom_ee.M();
 
  int nTracks = v.nTracks();
  int nSecondaryTracks = v.nSecondaryTracks();
  bool bPrimaryTracks = v.isTherePrimaryTracks();
  bool bMergedTracks = v.isThereMergedTracks();
 
  bool bPair = (nTracks == nSecondaryTracks) && (nTracks == 2);
  bool bOpposite = (c1 * c2 < -0.1);
  bool bDirection = ang < vertexIdentifier_.angle_V0Conv_max();
  bool bConvMass = mass_ee < vertexIdentifier_.mConv_max();
 
  bool bV0Conv = bPair && bOpposite && bDirection;
 
  // If the basic configuration of conversions and V0 decays is respected
  // pair of secondary track with opposite charge and going in the right direction
  // the selection is then based on mass limits
  if (bV0Conv) {
    // == (2.1) Identify Conversions == //
 
    bool isConv = bConvMass;
 
    if (isConv)
      return PFDisplacedVertex::CONVERSION_LOOSE;
 
    // == (2.2) Identify K0 == //
 
    double mass_pipi = mom_pipi.M();
 
    bool bK0Mass = mass_pipi < vertexIdentifier_.mK0_max() && mass_pipi > vertexIdentifier_.mK0_min();
 
    bool isK0 = bK0Mass;
 
    if (isK0)
      return PFDisplacedVertex::K0_DECAY;
 
    // == (2.3) Identify Lambda == //
 
    int lambdaKind = lambdaCP(v);
 
    bool isLambda = (lambdaKind == 1);
    bool isLambdaBar = (lambdaKind == -1);
 
    if (isLambda)
      return PFDisplacedVertex::LAMBDA_DECAY;
    if (isLambdaBar)
      return PFDisplacedVertex::LAMBDABAR_DECAY;
  }
 
  // == (2.4) Identify K- and K+ ==
  bool bK = (nSecondaryTracks == 1) && bPrimaryTracks && !bMergedTracks && !bOpposite;
 
  if (bK) {
    bool bKMass = isKaonMass(v);
 
    bool isKPlus = bKMass && c1 > 0;
    bool isKMinus = bKMass && c1 < 0;
 
    if (isKMinus)
      return PFDisplacedVertex::KMINUS_DECAY_LOOSE;
    if (isKPlus)
      return PFDisplacedVertex::KPLUS_DECAY_LOOSE;
  }
 
  // ===== (3) Identify Nuclears, Kinks and Remaining Fakes ===== //
 
  math::XYZTLorentzVector mom_prim = v.primaryMomentum(massPion, true);
 
  double p_prim = mom_prim.P();
  double p_sec = mom_pipi.P();
  double pt_prim = mom_prim.Pt();
 
  bool bLog = false;
  if (p_prim > 0.05 && p_sec > 0.05)
    bLog = log10(p_prim / p_sec) > vertexIdentifier_.logPrimSec_min();
  bool bPtMin = pt_prim > vertexIdentifier_.pt_kink_min();
 
  // A vertex with at least 3 tracks is considered as high purity nuclear interaction
  // the only exception is K- decay into 3 prongs. To be studied.
  bool isNuclearHighPurity = nTracks > 2 && mass_ee > vertexIdentifier_.mNucl_min();
  bool isFakeHighPurity = nTracks > 2 && mass_ee < vertexIdentifier_.mNucl_min();
  // Two secondary tracks with some minimal tracks angular opening are still accepted
  // as nuclear interactions
  bool isNuclearLowPurity = (nTracks == nSecondaryTracks) && (nTracks == 2) && mass_ee > vertexIdentifier_.mNucl_min();
 
  bool isFakeNucl = (nTracks == nSecondaryTracks) && (nTracks == 2) && mass_ee < vertexIdentifier_.mNucl_min();
 
  // Kinks: 1 primary + 1 secondary is accepted only if the primary tracks
  // has more energy than the secondary and primary have some minimal pT
  // to produce a nuclear interaction
  bool isNuclearKink = (nSecondaryTracks == 1) && bPrimaryTracks && !bMergedTracks && bLog && bPtMin;
 
  // Here some loopers may hide appearing in Particle Isolation plots. To be studied...
  bool isFakeKink = ((nSecondaryTracks == 1) && bMergedTracks && !bPrimaryTracks) ||
                    ((nSecondaryTracks == 1) && bPrimaryTracks && !bMergedTracks && (!bLog || !bPtMin));
 
  if (isNuclearHighPurity)
    return PFDisplacedVertex::NUCL;
  if (isNuclearLowPurity)
    return PFDisplacedVertex::NUCL_LOOSE;
  if (isFakeKink || isFakeNucl || isFakeHighPurity)
    return PFDisplacedVertex::FAKE;
  if (isNuclearKink)
    return PFDisplacedVertex::NUCL_KINK;
 
  return PFDisplacedVertex::ANY;
}

References PFDisplacedVertexHelper::VertexIdentifier::angle_max(), PFDisplacedVertexHelper::VertexIdentifier::angle_V0Conv_max(), cscdqm::ANY, alignmentValidation::c1, ALCARECOTkAlJpsiMuMu_cff::charge, sistrip::FAKE, PFDisplacedVertexHelper::VertexIdentifier::identifyVertices(), isKaonMass(), lambdaCP(), PFDisplacedVertexHelper::VertexIdentifier::logPrimSec_min(), PFDisplacedVertexHelper::VertexIdentifier::looper_eta_max(), PFDisplacedVertexHelper::VertexIdentifier::mConv_max(), PFDisplacedVertexHelper::VertexIdentifier::mK0_max(), PFDisplacedVertexHelper::VertexIdentifier::mK0_min(), PFDisplacedVertexHelper::VertexIdentifier::mNucl_min(), BeamSpotPI::nTracks, PFDisplacedVertexHelper::VertexIdentifier::pt_kink_min(), PFDisplacedVertexHelper::VertexIdentifier::pt_min(), findQualityFiles::v, and vertexIdentifier_.

Referenced by PFDisplacedVertexFinder::rejectAndLabelVertex().

isKaonMass()

bool PFDisplacedVertexHelper::isKaonMass ( const reco::PFDisplacedVertex &  v ) const

private

Definition at line 285 of file PFDisplacedVertexHelper.cc.

                                                                         {
  math::XYZVector trkInit = v.refittedTracks()[1].momentum();
  math::XYZVector trkFinal = v.refittedTracks()[0].momentum();
 
  if (v.trackTypes()[0] == PFDisplacedVertex::T_TO_VERTEX) {
    trkInit = v.refittedTracks()[0].momentum();
    trkFinal = v.refittedTracks()[1].momentum();
  }
 
  math::XYZVector trkNeutre(trkInit.x() - trkFinal.x(), trkInit.y() - trkFinal.y(), trkInit.z() - trkFinal.z());
 
  double Ec = sqrt(muon_mass2 + trkFinal.Mag2());
  double En = sqrt(0 * 0 + trkNeutre.Mag2());
 
  math::XYZTLorentzVectorD trkMuNu(trkInit.x(), trkInit.y(), trkInit.z(), Ec + En);
  double massMuNu = trkMuNu.M();
 
  bool bKMass = massMuNu > vertexIdentifier_.mK_min() && massMuNu < vertexIdentifier_.mK_max();
 
  return bKMass;
}

References PFDisplacedVertexHelper::VertexIdentifier::mK_max(), PFDisplacedVertexHelper::VertexIdentifier::mK_min(), muon_mass2, mathSSE::sqrt(), findQualityFiles::v, and vertexIdentifier_.

Referenced by identifyVertex().

isTrackSelected()

bool PFDisplacedVertexHelper::isTrackSelected	(	const reco::Track &	trk,
		const reco::PFDisplacedVertex::VertexTrackType	vertexTrackType
	)		const

Select tracks tool.

Definition at line 38 of file PFDisplacedVertexHelper.cc.

                                                                                                                {
  if (!tracksSelector_.selectTracks())
    return true;
 
  bool isGoodTrack = false;
 
  bool isHighPurity = trk.quality(trk.qualityByName(tracksSelector_.quality()));
 
  double nChi2 = trk.normalizedChi2();
  double pt = trk.pt();
  int nHits = trk.numberOfValidHits();
 
  bool bIsPrimary = ((vertexTrackType == reco::PFDisplacedVertex::T_TO_VERTEX) ||
                     (vertexTrackType == reco::PFDisplacedVertex::T_MERGED));
 
  if (bIsPrimary) {
    // Primary or merged track selection
    isGoodTrack = ((nChi2 > tracksSelector_.nChi2_min() && nChi2 < tracksSelector_.nChi2_max()) || isHighPurity) &&
                  pt > tracksSelector_.pt_min();
  } else {
    // Secondary tracks selection
    int nOuterHits = trk.hitPattern().numberOfLostHits(HitPattern::MISSING_OUTER_HITS);
 
    double dxy = trk.dxy(pvtx_);
 
    isGoodTrack = nChi2 < tracksSelector_.nChi2_max() && pt > tracksSelector_.pt_min() &&
                  fabs(dxy) > tracksSelector_.dxy_min() && nHits >= tracksSelector_.nHits_min() &&
                  nOuterHits <= tracksSelector_.nOuterHits_max();
  }
 
  return isGoodTrack;
}

References PVValHelper::dxy, reco::TrackBase::dxy(), PFDisplacedVertexHelper::TracksSelector::dxy_min(), reco::TrackBase::hitPattern(), PFDisplacedVertexHelper::TracksSelector::nChi2_max(), PFDisplacedVertexHelper::TracksSelector::nChi2_min(), PFDisplacedVertexHelper::TracksSelector::nHits_min(), reco::TrackBase::normalizedChi2(), PFDisplacedVertexHelper::TracksSelector::nOuterHits_max(), reco::HitPattern::numberOfLostHits(), reco::TrackBase::numberOfValidHits(), DiDispStaMuonMonitor_cfi::pt, reco::TrackBase::pt(), PFDisplacedVertexHelper::TracksSelector::pt_min(), pvtx_, PFDisplacedVertexHelper::TracksSelector::quality(), reco::TrackBase::quality(), reco::TrackBase::qualityByName(), PFDisplacedVertexHelper::TracksSelector::selectTracks(), reco::PFDisplacedVertex::T_MERGED, reco::PFDisplacedVertex::T_TO_VERTEX, and tracksSelector_.

Referenced by PFDisplacedVertexFinder::fitVertexFromSeed().

lambdaCP()

int PFDisplacedVertexHelper::lambdaCP ( const reco::PFDisplacedVertex &  v ) const

private

Tools used to calculate quantities for vertex identification.

Definition at line 214 of file PFDisplacedVertexHelper.cc.

                                                                      {
  int lambdaCP = 0;
 
  vector<Track> refittedTracks = v.refittedTracks();
 
  math::XYZTLorentzVector totalMomentumDcaRefit_lambda;
  math::XYZTLorentzVector totalMomentumDcaRefit_lambdabar;
 
  reco::Track tMomentumDcaRefit_0 = refittedTracks[0];
  reco::Track tMomentumDcaRefit_1 = refittedTracks[1];
 
  double mass2_0 = 0, mass2_1 = 0;
 
  int c1 = v.originalTrack(v.refittedTracks()[1])->charge();
 
  // --------------------------- lambda --------------------
 
  if (c1 > 0.1)
    mass2_0 = pion_mass2, mass2_1 = proton_mass2;
  else
    mass2_0 = proton_mass2, mass2_1 = pion_mass2;
 
  double E = sqrt(tMomentumDcaRefit_0.p() * tMomentumDcaRefit_0.p() + mass2_0);
 
  math::XYZTLorentzVector momentumDcaRefit_0(
      tMomentumDcaRefit_0.px(), tMomentumDcaRefit_0.py(), tMomentumDcaRefit_0.pz(), E);
 
  E = sqrt(tMomentumDcaRefit_1.p() * tMomentumDcaRefit_1.p() + mass2_1);
 
  math::XYZTLorentzVector momentumDcaRefit_1(
      tMomentumDcaRefit_1.px(), tMomentumDcaRefit_1.py(), tMomentumDcaRefit_1.pz(), E);
 
  totalMomentumDcaRefit_lambda = momentumDcaRefit_0 + momentumDcaRefit_1;
 
  // --------------------------- anti - lambda --------------------
 
  if (c1 > 0.1)
    mass2_1 = pion_mass2, mass2_0 = proton_mass2;
  else
    mass2_1 = proton_mass2, mass2_0 = pion_mass2;
 
  E = sqrt(tMomentumDcaRefit_0.p() * tMomentumDcaRefit_0.p() + mass2_0);
 
  math::XYZTLorentzVector momentumDcaRefit_01(
      tMomentumDcaRefit_0.px(), tMomentumDcaRefit_0.py(), tMomentumDcaRefit_0.pz(), E);
 
  E = sqrt(tMomentumDcaRefit_1.p() * tMomentumDcaRefit_1.p() + mass2_1);
 
  math::XYZTLorentzVector momentumDcaRefit_11(
      tMomentumDcaRefit_1.px(), tMomentumDcaRefit_1.py(), tMomentumDcaRefit_1.pz(), E);
 
  totalMomentumDcaRefit_lambdabar = momentumDcaRefit_01 + momentumDcaRefit_11;
 
  double mass_l = totalMomentumDcaRefit_lambda.M();
  double mass_lbar = totalMomentumDcaRefit_lambdabar.M();
 
  //  cout << "mass_l = " << mass_l << " mass_lbar = " <<  mass_lbar << endl;
 
  if (mass_l < mass_lbar && mass_l > vertexIdentifier_.mLambda_min() && mass_l < vertexIdentifier_.mLambda_max())
    lambdaCP = 1;
  else if (mass_lbar < mass_l && mass_lbar > vertexIdentifier_.mLambda_min() &&
           mass_lbar < vertexIdentifier_.mLambda_max())
    lambdaCP = -1;
  else
    lambdaCP = 0;
 
  //cout << "lambdaCP = " << lambdaCP << endl;
 
  return lambdaCP;
}

References alignmentValidation::c1, ALCARECOTkAlJpsiMuMu_cff::charge, PFDisplacedVertexHelper::VertexIdentifier::mLambda_max(), PFDisplacedVertexHelper::VertexIdentifier::mLambda_min(), reco::TrackBase::p(), pion_mass2, proton_mass2, reco::TrackBase::px(), reco::TrackBase::py(), reco::TrackBase::pz(), tkAlTrackRefitSequence_cff::refittedTracks, mathSSE::sqrt(), findQualityFiles::v, and vertexIdentifier_.

Referenced by identifyVertex().

primaryVertex()

math::XYZPoint PFDisplacedVertexHelper::primaryVertex ( ) const

inline

Set Vertex direction using the primary vertex.

Definition at line 39 of file PFDisplacedVertexHelper.h.

{ return pvtx_; }

References pvtx_.

Referenced by PFDisplacedVertexFinder::fitVertexFromSeed().

setPrimaryVertex()

void PFDisplacedVertexHelper::setPrimaryVertex	(	edm::Handle< reco::VertexCollection >	mainVertexHandle,
		edm::Handle< reco::BeamSpot >	beamSpotHandle
	)

Update the primary vertex information.

Definition at line 23 of file PFDisplacedVertexHelper.cc.

                                                                                       {
  const math::XYZPoint beamSpot = beamSpotHandle.isValid()
                                      ? math::XYZPoint(beamSpotHandle->x0(), beamSpotHandle->y0(), beamSpotHandle->z0())
                                      : math::XYZPoint(0, 0, 0);
 
  // The primary vertex is taken from the refitted list,
  // if does not exist from the average offline beam spot position
  // if does not exist (0,0,0) is used
  pvtx_ = mainVertexHandle.isValid()
              ? math::XYZPoint(
                    mainVertexHandle->begin()->x(), mainVertexHandle->begin()->y(), mainVertexHandle->begin()->z())
              : beamSpot;
}

References pwdgSkimBPark_cfi::beamSpot, edm::HandleBase::isValid(), pvtx_, reco::BeamSpot::x0(), reco::BeamSpot::y0(), and reco::BeamSpot::z0().

Referenced by PFDisplacedVertexFinder::setPrimaryVertex().

setTracksSelector()

void PFDisplacedVertexHelper::setTracksSelector ( const edm::ParameterSet &  ps )

inline

Set Tracks selector parameters.

Definition at line 23 of file PFDisplacedVertexHelper.h.

{ tracksSelector_ = TracksSelector(ps); };

References tracksSelector_.

Referenced by PFDisplacedVertexFinder::setTracksSelector().

setVertexIdentifier()

void PFDisplacedVertexHelper::setVertexIdentifier ( const edm::ParameterSet &  ps )

inline

Set Vertex identifier parameters.

Definition at line 26 of file PFDisplacedVertexHelper.h.

{ vertexIdentifier_ = VertexIdentifier(ps); };

References vertexIdentifier_.

Referenced by PFDisplacedVertexFinder::setVertexIdentifier().

Member Data Documentation

muon_mass2

const double PFDisplacedVertexHelper::muon_mass2 = 0.106 * 0.106

staticprivate

Definition at line 182 of file PFDisplacedVertexHelper.h.

Referenced by isKaonMass().

pion_mass2

const double PFDisplacedVertexHelper::pion_mass2 = 0.0194

staticprivate

Masses2 taken from PDG.

Definition at line 181 of file PFDisplacedVertexHelper.h.

Referenced by lambdaCP().

proton_mass2

const double PFDisplacedVertexHelper::proton_mass2 = 0.938 * 0.938

staticprivate

Definition at line 183 of file PFDisplacedVertexHelper.h.

Referenced by lambdaCP().

pvtx_

math::XYZPoint PFDisplacedVertexHelper::pvtx_

private

Primary vertex information updated for each event.

Definition at line 178 of file PFDisplacedVertexHelper.h.

Referenced by Dump(), isTrackSelected(), primaryVertex(), and setPrimaryVertex().

tracksSelector_

TracksSelector PFDisplacedVertexHelper::tracksSelector_

private

Definition at line 175 of file PFDisplacedVertexHelper.h.

Referenced by Dump(), isTrackSelected(), and setTracksSelector().

vertexIdentifier_

VertexIdentifier PFDisplacedVertexHelper::vertexIdentifier_

private

Definition at line 176 of file PFDisplacedVertexHelper.h.

Referenced by Dump(), identifyVertex(), isKaonMass(), lambdaCP(), and setVertexIdentifier().