EgammaHLTTrackIsolation Class Reference

#include <RecoEgamma/EgammaHLTAlgos/interface/EgammaHLTTrackIsolation.h>

Public Member Functions
	EgammaHLTTrackIsolation (double egTrkIso_PtMin, double egTrkIso_ConeSize, double egTrkIso_ZSpan, double egTrkIso_RSpan, double egTrkIso_VetoConeSize, double egTrkIso_stripBarrel=0, double egTrkIso_stripEndcap=0)
std::pair< int, float >	electronIsolation (const reco::Track *const tr, const reco::TrackCollection *isoTracks)
	Get number of tracks and Pt sum of tracks inside an isolation cone for electrons. More...
std::pair< int, float >	electronIsolation (const reco::Track *const tr, const reco::ElectronCollection *allEle, const reco::TrackCollection *isoTracks)
std::pair< int, float >	electronIsolation (const reco::Track *const tr, const reco::TrackCollection *isoTracks, GlobalPoint vertex)
float	electronPtSum (const reco::Track *const tr, const reco::TrackCollection *isoTracks)
	Get Pt sum of tracks inside an isolation cone for electrons. More...
float	electronPtSum (const reco::Track *const tr, const reco::TrackCollection *isoTracks, GlobalPoint vertex)
float	electronPtSum (const reco::Track *const tr, const reco::ElectronCollection *allEle, const reco::TrackCollection *isoTracks)
int	electronTrackCount (const reco::Track *const tr, const reco::TrackCollection *isoTracks)
	Get number of tracks inside an isolation cone for electrons. More...
int	electronTrackCount (const reco::Track *const tr, const reco::TrackCollection *isoTracks, GlobalPoint vertex)
double	getConeSize ()
	Get isolation cone size. More...
double	getPtMin ()
	Get pt cut for itracks. More...
double	getRspan ()
	Get maximum transverse distance of ivertex from beam line. More...
double	getvetoConesize ()
	Get veto cone size. More...
double	getZspan ()
	Get maximum ivertex z-coordinate spread. More...
std::pair< int, float >	photonIsolation (const reco::RecoCandidate *const recocand, const reco::TrackCollection *isoTracks, bool useVertex)
std::pair< int, float >	photonIsolation (const reco::RecoCandidate *const recocand, const reco::TrackCollection *isoTracks, GlobalPoint vertex)
std::pair< int, float >	photonIsolation (const reco::RecoCandidate *const recocand, const reco::ElectronCollection *allEle, const reco::TrackCollection *isoTracks)
float	photonPtSum (const reco::RecoCandidate *const recocand, const reco::TrackCollection *isoTracks, bool useVertex)
float	photonPtSum (const reco::RecoCandidate *const recocand, const reco::TrackCollection *isoTracks, GlobalPoint vertex)
float	photonPtSum (const reco::RecoCandidate *const recocand, const reco::ElectronCollection *allEle, const reco::TrackCollection *isoTracks)
int	photonTrackCount (const reco::RecoCandidate *const recocand, const reco::TrackCollection *isoTracks, bool useVertex)
int	photonTrackCount (const reco::RecoCandidate *const recocand, const reco::TrackCollection *isoTracks, GlobalPoint vertex)
int	photonTrackCount (const reco::RecoCandidate *const recocand, const reco::ElectronCollection *allEle, const reco::TrackCollection *isoTracks)

Private Member Functions
std::pair< int, float >	findIsoTracks (GlobalVector mom, GlobalPoint vtx, const reco::TrackCollection *isoTracks, bool isElectron, bool useVertex=true)
std::pair< int, float >	findIsoTracksWithoutEle (GlobalVector mom, GlobalPoint vtx, const reco::ElectronCollection *allEle, const reco::TrackCollection *isoTracks)

Private Attributes
double	conesize
double	ptMin
double	rspan
double	stripBarrel
double	stripEndcap
double	vetoConesize
double	zspan

Detailed Description

Description: Number of tracks inside an isolation cone, with con geometry defined by ptMin, conesize, rspan and zspan. Usage: <usage>

Definition at line 47 of file EgammaHLTTrackIsolation.h.

Constructor & Destructor Documentation

EgammaHLTTrackIsolation::EgammaHLTTrackIsolation ( double  egTrkIso_PtMin, double  egTrkIso_ConeSize, double  egTrkIso_ZSpan, double  egTrkIso_RSpan, double  egTrkIso_VetoConeSize, double  egTrkIso_stripBarrel = 0, double  egTrkIso_stripEndcap = 0  )

inline

Definition at line 53 of file EgammaHLTTrackIsolation.h.

References electronIsolation(), photonIsolation(), and VerticesFromLeptons_cfi::useVertex.

                                             :
    ptMin(egTrkIso_PtMin),
    conesize(egTrkIso_ConeSize),
    zspan(egTrkIso_ZSpan),
    rspan(egTrkIso_RSpan),
    vetoConesize(egTrkIso_VetoConeSize),
    stripBarrel(egTrkIso_stripBarrel),
    stripEndcap(egTrkIso_stripEndcap)
  {
      
      /*
    std::cout << "EgammaHLTTrackIsolation instance:"
    << " ptMin=" << ptMin << " "
    << " conesize="<< conesize << " "
    << " zspan=" << zspan << " "
    << " rspan=" << rspan << " "
    << " vetoConesize="<< vetoConesize
    << std::endl;    
      */
    }

Member Function Documentation

std::pair< int, float > EgammaHLTTrackIsolation::electronIsolation	(	const reco::Track *const	tr,
		const reco::TrackCollection *	isoTracks
	)

Get number of tracks and Pt sum of tracks inside an isolation cone for electrons.

Definition at line 19 of file EgammaHLTTrackIsolation.cc.

References findIsoTracks(), reco::TrackBase::momentum(), AlCaHLTBitMon_ParallelJobs::p, reco::TrackBase::vertex(), and badGlobalMuonTaggersAOD_cff::vtx.

Referenced by EgammaHLTTrackIsolation(), electronPtSum(), and electronTrackCount().

{
  GlobalPoint vtx(0,0,tr->vertex().z());
  const reco::Track::Vector& p = tr->momentum();
  GlobalVector mom( p.x(), p.y(), p.z() );
  return findIsoTracks(mom,vtx,isoTracks,true);
}

std::pair< int, float > EgammaHLTTrackIsolation::electronIsolation	(	const reco::Track *const	tr,
		const reco::ElectronCollection *	allEle,
		const reco::TrackCollection *	isoTracks
	)

Definition at line 37 of file EgammaHLTTrackIsolation.cc.

References findIsoTracksWithoutEle(), reco::TrackBase::momentum(), AlCaHLTBitMon_ParallelJobs::p, reco::TrackBase::vertex(), and badGlobalMuonTaggersAOD_cff::vtx.

{
  GlobalPoint vtx(0,0,tr->vertex().z());
  const reco::Track::Vector& p = tr->momentum();
  GlobalVector mom( p.x(), p.y(), p.z() );
  return findIsoTracksWithoutEle(mom,vtx,allEle,isoTracks);
}

std::pair< int, float > EgammaHLTTrackIsolation::electronIsolation	(	const reco::Track *const	tr,
		const reco::TrackCollection *	isoTracks,
		GlobalPoint	vertex
	)

Definition at line 28 of file EgammaHLTTrackIsolation.cc.

References findIsoTracks(), reco::TrackBase::momentum(), AlCaHLTBitMon_ParallelJobs::p, badGlobalMuonTaggersAOD_cff::vtx, and PV3DBase< T, PVType, FrameType >::z().

{ 
  // Just to insure consistency with no-vertex-code
  GlobalPoint vtx(0,0,zvtx.z());
  const reco::Track::Vector& p = tr->momentum();
  GlobalVector mom( p.x(), p.y(), p.z() );
  return findIsoTracks(mom,vtx,isoTracks,true);
}

float EgammaHLTTrackIsolation::electronPtSum ( const reco::Track *const  tr, const reco::TrackCollection *  isoTracks  )

inline

Get Pt sum of tracks inside an isolation cone for electrons.

Definition at line 110 of file EgammaHLTTrackIsolation.h.

References electronIsolation().

Referenced by egHLT::OffHelper::fillIsolData().

  {return electronIsolation(tr,isoTracks).second;}

float EgammaHLTTrackIsolation::electronPtSum ( const reco::Track *const  tr, const reco::TrackCollection *  isoTracks, GlobalPoint  vertex  )

inline

Definition at line 112 of file EgammaHLTTrackIsolation.h.

References electronIsolation().

  {return electronIsolation(tr,isoTracks,vertex).second;}

float EgammaHLTTrackIsolation::electronPtSum ( const reco::Track *const  tr, const reco::ElectronCollection *  allEle, const reco::TrackCollection *  isoTracks  )

inline

Definition at line 114 of file EgammaHLTTrackIsolation.h.

References electronIsolation().

  {return electronIsolation(tr,allEle,isoTracks).second;} 

int EgammaHLTTrackIsolation::electronTrackCount ( const reco::Track *const  tr, const reco::TrackCollection *  isoTracks  )

inline

Get number of tracks inside an isolation cone for electrons.

Definition at line 94 of file EgammaHLTTrackIsolation.h.

References electronIsolation().

  {return electronIsolation(tr,isoTracks).first;}

int EgammaHLTTrackIsolation::electronTrackCount ( const reco::Track *const  tr, const reco::TrackCollection *  isoTracks, GlobalPoint  vertex  )

inline

Definition at line 96 of file EgammaHLTTrackIsolation.h.

References electronIsolation().

  {return electronIsolation(tr,isoTracks,vertex).first;}

std::pair< int, float > EgammaHLTTrackIsolation::findIsoTracks ( GlobalVector  mom, GlobalPoint  vtx, const reco::TrackCollection *  isoTracks, bool  isElectron, bool  useVertex = true  )

private

Definition at line 82 of file EgammaHLTTrackIsolation.cc.

References PVValHelper::dz, PV3DBase< T, PVType, FrameType >::eta(), M_PI, ntrack, PV3DBase< T, PVType, FrameType >::perp(), PV3DBase< T, PVType, FrameType >::phi(), EnergyCorrector::pt, ptMin, dttmaxenums::R, rspan, mathSSE::sqrt(), stripBarrel, stripEndcap, vetoConesize, PV3DBase< T, PVType, FrameType >::z(), and zspan.

Referenced by electronIsolation(), getvetoConesize(), and photonIsolation().

{

  // Check that reconstructed tracks fit within cone boundaries,
  // (Note: tracks will not always stay within boundaries)
  int ntrack = 0;
  float ptSum = 0.;

  for(reco::TrackCollection::const_iterator trItr = isoTracks->begin(); trItr != isoTracks->end(); ++trItr){

    GlobalPoint ivtx(trItr->vertex().x(),trItr->vertex().y(),trItr->vertex().z());
    reco::Track::Vector ip = trItr->momentum();
    GlobalVector imom ( ip.x(), ip.y(), ip.z());

    float pt = imom.perp();
    float dperp = 0.;
    float dz = 0.;
    float deta = 0.;
    float dphi = 0.;
    if (useVertex) {
      dperp = ivtx.perp()-vtx.perp();
      dz = ivtx.z()-vtx.z();
      deta = imom.eta()-mom.eta();
      dphi = imom.phi()-mom.phi();
    } else {
      //in case of unkown photon vertex, modify direction of photon to point from
      //current track vertex to sc instead of from (0.,0.,0.) to sc.  In this 
      //way, all tracks are considered based on direction alone.
      GlobalVector mom_temp = mom - GlobalVector(ivtx.x(),ivtx.y(),ivtx.z());
      deta = imom.eta()-mom_temp.eta();
      dphi = imom.phi()-mom_temp.phi();
    }
    // Correct dmom_phi's from [-2pi,2pi] to [-pi,pi]
    if (dphi>M_PI) dphi = dphi - 2*M_PI;
    else if (dphi<-M_PI) dphi = dphi + 2*M_PI;

    float R = sqrt( dphi*dphi + deta*deta );

    // Apply boundary cut
    // bool selected=false;

    // if (pt > ptMin && R < conesize &&
    //  fabs(dperp) < rspan && fabs(dz) < zspan) selected=true;
  
    // if (selected) {
    //  ntrack++;
    //  if (!isElectron || R > vetoConesize) ptSum+=pt; //to exclude electron track
    // }
    // float theVetoVar = R;
    // if (isElectron) theVetoVar = R;  
    
    //hmm how do I figure out if this is barrel or endcap?
    //abs(mom.eta())<1.5 is the obvious choice but that will be electron not detector eta for electrons
    //well lets leave it as that for now, its what reco does (well with eta=1.479)
    double innerStrip = fabs(mom.eta())<1.479 ? stripBarrel : stripEndcap;
    
    if (pt > ptMin && R < conesize && R > vetoConesize &&
        fabs(dperp) < rspan && fabs(dz) < zspan &&
    fabs(deta) >=innerStrip) {
      ntrack++;
      ptSum+=pt; 
    }
  }

  // if (isElectron) ntrack-=1; //to exclude electron track

  return (std::pair<int,float>(ntrack,ptSum));

}

std::pair< int, float > EgammaHLTTrackIsolation::findIsoTracksWithoutEle ( GlobalVector  mom, GlobalPoint  vtx, const reco::ElectronCollection *  allEle, const reco::TrackCollection *  isoTracks  )

private

Definition at line 152 of file EgammaHLTTrackIsolation.cc.

References conesize, PVValHelper::dz, PV3DBase< T, PVType, FrameType >::eta(), M_PI, ntrack, PV3DBase< T, PVType, FrameType >::perp(), PV3DBase< T, PVType, FrameType >::phi(), EnergyCorrector::pt, ptMin, dttmaxenums::R, rspan, mathSSE::sqrt(), stripBarrel, stripEndcap, vetoConesize, PV3DBase< T, PVType, FrameType >::z(), and zspan.

Referenced by electronIsolation(), getvetoConesize(), and photonIsolation().

{

  // Check that reconstructed tracks fit within cone boundaries,
  // (Note: tracks will not always stay within boundaries)
  int iele = 0;
  int ntrack = 0;
  float ptSum = 0.;
  std::vector<float> etaele;
  std::vector<float> phiele;

  // std::cout << "allEle.size() = " << allEle->size() << std::endl;

  // Store ALL electrons eta and phi
  for (reco::ElectronCollection::const_iterator iElectron = allEle->begin(); iElectron != allEle->end(); iElectron++){
    iele++;
    reco::TrackRef anothereletrackref = iElectron->track();
    etaele.push_back(anothereletrackref->momentum().eta());
    phiele.push_back(anothereletrackref->momentum().phi());
    // std::cout << "Electron " << iele << ": phi = " << anothereletrackref->momentum().phi() << ", eta = " << anothereletrackref->momentum().eta() << std::endl; 
  }
  
  for(reco::TrackCollection::const_iterator trItr = isoTracks->begin(); trItr != isoTracks->end(); ++trItr){

    GlobalPoint ivtx(trItr->vertex().x(),trItr->vertex().y(),trItr->vertex().z());
    reco::Track::Vector ip = trItr->momentum();
    GlobalVector imom ( ip.x(), ip.y(), ip.z());

    float pt = imom.perp();
    float dperp = ivtx.perp()-vtx.perp();
    float dz = ivtx.z()-vtx.z();
    float deta = imom.eta()-mom.eta();
    float dphi = imom.phi()-mom.phi();
    
    // Correct dmom_phi's from [-2pi,2pi] to [-pi,pi]
    if (dphi>M_PI) dphi = dphi - 2*M_PI;
    else if (dphi<-M_PI) dphi = dphi + 2*M_PI;

    float R = sqrt( dphi*dphi + deta*deta );

    // Apply boundary cut
    bool selected=false;
    bool passedconeveto=true;

    //hmm how do I figure out if this is barrel or endcap?
    //abs(mom.eta())<1.5 is the obvious choice but that will be electron not detector eta for electrons
    //well lets leave it as that for now, its what reco does (well with eta=1.479)
    double innerStrip = fabs(mom.eta())<1.479 ? stripBarrel : stripEndcap;

    if (pt > ptMin && R < conesize &&
    fabs(dperp) < rspan && fabs(dz) < zspan && 
    fabs(deta) >=innerStrip) selected=true;
  
    // Check that NO electron is counted in the isolation
    for(unsigned int eleItr = 0; eleItr < etaele.size(); ++eleItr){
    
      deta = etaele[eleItr] - imom.eta();
      dphi = phiele[eleItr] - imom.phi();

      // Correct dmom_phi's from [-2pi,2pi] to [-pi,pi]
      if (dphi>M_PI) dphi = dphi - 2*M_PI;
      else if (dphi<-M_PI) dphi = dphi + 2*M_PI;

      R = sqrt( dphi*dphi + deta*deta );
      if (R < vetoConesize) passedconeveto=false;
    }

    if (selected && passedconeveto) {
      ntrack++;
      ptSum+=pt; //to exclude electron tracks
    }

  }

  // ntrack-=1; //to exclude electron track

  return (std::pair<int,float>(ntrack,ptSum));

}

double EgammaHLTTrackIsolation::getConeSize ( )

inline

Get isolation cone size.

Definition at line 131 of file EgammaHLTTrackIsolation.h.

References conesize.

{ return conesize; }

double EgammaHLTTrackIsolation::getPtMin ( )

inline

Get pt cut for itracks.

Definition at line 129 of file EgammaHLTTrackIsolation.h.

References ptMin.

{ return ptMin;}

double EgammaHLTTrackIsolation::getRspan ( )

inline

Get maximum transverse distance of ivertex from beam line.

Definition at line 135 of file EgammaHLTTrackIsolation.h.

References rspan.

{ return rspan; }

double EgammaHLTTrackIsolation::getvetoConesize ( )

inline

Get veto cone size.

Definition at line 137 of file EgammaHLTTrackIsolation.h.

References findIsoTracks(), findIsoTracksWithoutEle(), reco::isElectron(), vetoConesize, and badGlobalMuonTaggersAOD_cff::vtx.

{ return vetoConesize; }

double EgammaHLTTrackIsolation::getZspan ( )

inline

Get maximum ivertex z-coordinate spread.

Definition at line 133 of file EgammaHLTTrackIsolation.h.

References zspan.

{return zspan; }

std::pair< int, float > EgammaHLTTrackIsolation::photonIsolation	(	const reco::RecoCandidate *const	recocand,
		const reco::TrackCollection *	isoTracks,
		bool	useVertex
	)

Get number of tracks and Pt sum of tracks inside an isolation cone for photons set useVertex=true to use PhotonCandidate vertex from EgammaPhotonVtxFinder set useVertex=false to consider all tracks for isolation

Definition at line 45 of file EgammaHLTTrackIsolation.cc.

References findIsoTracks(), reco::RecoCandidate::superCluster(), reco::LeafCandidate::vertex(), and badGlobalMuonTaggersAOD_cff::vtx.

Referenced by EgammaHLTTrackIsolation(), photonPtSum(), and photonTrackCount().

{

  if (useVertex) {
    GlobalPoint vtx(0,0,recocandidate->vertex().z());
    return photonIsolation(recocandidate,isoTracks,vtx);
  } else {
    reco::RecoCandidate::Point pos = recocandidate->superCluster()->position();
    GlobalVector mom(pos.x(),pos.y(),pos.z());
    return findIsoTracks(mom,GlobalPoint(),isoTracks,false,false);
  }

}

std::pair< int, float > EgammaHLTTrackIsolation::photonIsolation	(	const reco::RecoCandidate *const	recocand,
		const reco::TrackCollection *	isoTracks,
		GlobalPoint	vertex
	)

Definition at line 59 of file EgammaHLTTrackIsolation.cc.

References findIsoTracks(), reco::RecoCandidate::superCluster(), badGlobalMuonTaggersAOD_cff::vtx, and PV3DBase< T, PVType, FrameType >::z().

{

  // to insure consistency with no-free-vertex-code
  GlobalPoint vtx(0,0,zvtx.z());

  reco::RecoCandidate::Point pos = recocandidate->superCluster()->position();
  GlobalVector mom(pos.x()-vtx.x(),pos.y()-vtx.y(),pos.z()-vtx.z());

  return findIsoTracks(mom,vtx,isoTracks,false);

}

std::pair< int, float > EgammaHLTTrackIsolation::photonIsolation	(	const reco::RecoCandidate *const	recocand,
		const reco::ElectronCollection *	allEle,
		const reco::TrackCollection *	isoTracks
	)

Definition at line 73 of file EgammaHLTTrackIsolation.cc.

References findIsoTracksWithoutEle(), and reco::RecoCandidate::superCluster().

{

  reco::RecoCandidate::Point pos = recocandidate->superCluster()->position();
  GlobalVector mom(pos.x(),pos.y(),pos.z());
  return findIsoTracksWithoutEle(mom,GlobalPoint(),allEle,isoTracks);

}

float EgammaHLTTrackIsolation::photonPtSum ( const reco::RecoCandidate *const  recocand, const reco::TrackCollection *  isoTracks, bool  useVertex  )

inline

Get Pt sum of tracks inside an isolation cone for photons set useVertex=true to use Photon vertex from EgammaPhotonVtxFinder set useVertex=false to consider all tracks for isolation

Definition at line 120 of file EgammaHLTTrackIsolation.h.

References photonIsolation().

Referenced by egHLT::OffHelper::fillIsolData(), and EgammaHLTPhotonTrackIsolationProducersRegional::produce().

  {return photonIsolation(recocand,isoTracks, useVertex).second;}

float EgammaHLTTrackIsolation::photonPtSum ( const reco::RecoCandidate *const  recocand, const reco::TrackCollection *  isoTracks, GlobalPoint  vertex  )

inline

Definition at line 122 of file EgammaHLTTrackIsolation.h.

References photonIsolation().

  {return photonIsolation(recocand,isoTracks, vertex).second;}

float EgammaHLTTrackIsolation::photonPtSum ( const reco::RecoCandidate *const  recocand, const reco::ElectronCollection *  allEle, const reco::TrackCollection *  isoTracks  )

inline

Definition at line 124 of file EgammaHLTTrackIsolation.h.

References photonIsolation().

  {return photonIsolation(recocand,allEle,isoTracks).second;}

int EgammaHLTTrackIsolation::photonTrackCount ( const reco::RecoCandidate *const  recocand, const reco::TrackCollection *  isoTracks, bool  useVertex  )

inline

Get number of tracks inside an isolation cone for photons set useVertex=true to use Photon vertex from EgammaPhotonVtxFinder set useVertex=false to consider all tracks for isolation

Definition at line 102 of file EgammaHLTTrackIsolation.h.

References photonIsolation().

Referenced by egHLT::OffHelper::fillIsolData(), and EgammaHLTPhotonTrackIsolationProducersRegional::produce().

  {return photonIsolation(recocand,isoTracks,useVertex).first;}

int EgammaHLTTrackIsolation::photonTrackCount ( const reco::RecoCandidate *const  recocand, const reco::TrackCollection *  isoTracks, GlobalPoint  vertex  )

inline

Definition at line 104 of file EgammaHLTTrackIsolation.h.

References photonIsolation().

  {return photonIsolation(recocand,isoTracks,vertex).first;}

int EgammaHLTTrackIsolation::photonTrackCount ( const reco::RecoCandidate *const  recocand, const reco::ElectronCollection *  allEle, const reco::TrackCollection *  isoTracks  )

inline

Definition at line 106 of file EgammaHLTTrackIsolation.h.

References photonIsolation().

  {return photonIsolation(recocand,allEle,isoTracks).first;}

Member Data Documentation

double EgammaHLTTrackIsolation::conesize

private

Definition at line 146 of file EgammaHLTTrackIsolation.h.

Referenced by findIsoTracksWithoutEle(), and getConeSize().

double EgammaHLTTrackIsolation::ptMin

private

Definition at line 145 of file EgammaHLTTrackIsolation.h.

Referenced by findIsoTracks(), findIsoTracksWithoutEle(), and getPtMin().

double EgammaHLTTrackIsolation::rspan

private

Definition at line 148 of file EgammaHLTTrackIsolation.h.

Referenced by findIsoTracks(), findIsoTracksWithoutEle(), and getRspan().

double EgammaHLTTrackIsolation::stripBarrel

private

Definition at line 152 of file EgammaHLTTrackIsolation.h.

Referenced by findIsoTracks(), and findIsoTracksWithoutEle().

double EgammaHLTTrackIsolation::stripEndcap

private

Definition at line 153 of file EgammaHLTTrackIsolation.h.

Referenced by findIsoTracks(), and findIsoTracksWithoutEle().

double EgammaHLTTrackIsolation::vetoConesize

private

Definition at line 149 of file EgammaHLTTrackIsolation.h.

Referenced by findIsoTracks(), findIsoTracksWithoutEle(), and getvetoConesize().

double EgammaHLTTrackIsolation::zspan

private

Definition at line 147 of file EgammaHLTTrackIsolation.h.

Referenced by findIsoTracks(), findIsoTracksWithoutEle(), and getZspan().