InDetAlignTrackSelTool.cxx

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
 
// InDetAlignTrackSelTool.h
 
// Sergio Gonzalez Sevilla, started 04/7/05
// Miguel Olivo Gomez, extended 07/6/06
 
// AlgTool to select high quality tracks for the inner detector 
// (Pixel+SCT) alignment algorithms.
// This AlgTool provides a track selection based on the following cut variables:
// Momentum, pt, number of shared hits, number of holes and chi2 probability. 
// Returns 0 in case a track is not accepted, otherwise 1
 
#include "InDetAlignTrackSelTool.h"
 
#include "xAODTracking/TrackParticle.h"
#include "TrkToolInterfaces/ITrackParticleCreatorTool.h"
 
#include "TrkParameters/TrackParameters.h"
#include "TrkEventPrimitives/FitQuality.h"
#include "CLHEP/GenericFunctions/CumulativeChiSquare.hh"
 
InDetAlignTrackSelTool::InDetAlignTrackSelTool( const std::string& type
                        , const std::string& name
                        , const IInterface* parent
                        )
  : AthAlgTool(type,name,parent),
    m_particleCreator("Trk::TrackParticleCreatorTool/TrackParticleCreatorTool", this),
    m_minMomentum(0),
    m_minPt(2),
    m_maxShared(0),
    m_maxHoles(1),
    m_minChi2Prob(0.2)
{
  declareInterface<IInDetAlignTrackSelTool>(this);
  declareProperty("MinMomentum"        , m_minMomentum);
  declareProperty("MinPt"              , m_minPt);
  declareProperty("MaxShared"          , m_maxShared);
  declareProperty("MaxHoles"           , m_maxHoles);
  declareProperty("MinChi2Prob"        , m_minChi2Prob);
 
  // Tools
  declareProperty("TrackParticleCreatorTool", m_particleCreator,
                  "tool to build TrackParticle");
}
 
InDetAlignTrackSelTool::~InDetAlignTrackSelTool()
{}

StatusCode InDetAlignTrackSelTool::initialize(){
 
  // get TrackParticleCreatorTool
  ATH_CHECK(m_particleCreator.retrieve());
  
  ATH_MSG_DEBUG( "Cuts selected : min_Momentum(CLHEP::GeV)=" <<  m_minMomentum
        << " min_pt(CLHEP::GeV)=" <<  m_minPt
        << " max_shared=" << m_maxShared
        << " max_holes=" << m_maxHoles
        << " min_chi2Prob=" << m_minChi2Prob ) ;
 
  ATH_MSG_DEBUG( "InDetAlignTrackSelTool initialize() successful" ) ;
  return StatusCode::SUCCESS;
}

StatusCode InDetAlignTrackSelTool::finalize(){
  ATH_MSG_DEBUG( "InDetAlignTrackSelTool finalize method called" ) ;
  return StatusCode::SUCCESS;
}

double InDetAlignTrackSelTool::Momentum(const Trk::Track& track) const {
  ATH_MSG_DEBUG( "in Momentum() " ) ;
  double mom=0.;
 
  // get measured perigee and momentum of track
  const Trk::Perigee* perigee = track.perigeeParameters();
 
  if ( !perigee->covariance()) {
    ATH_MSG_ERROR( "No measured perigee parameters assigned to the track" ) ; 
    mom = -1e12; // return big value
  }
  else{
    Amg::VectorX perigeeParams = perigee->parameters();
    mom = std::abs(1./perigeeParams[Trk::qOverP]);
    mom /= 1000.; //mom in GeV
  }
 
  return mom;
}

double InDetAlignTrackSelTool::Pt(const Trk::Track& track) const {
  ATH_MSG_DEBUG( "in Pt() " ) ;
  double pt=0.;
 
  // get measured perigee and pt of track
  const Trk::Perigee* perigee = track.perigeeParameters();
 
  if (!perigee->covariance()) {
    ATH_MSG_ERROR( "No measured perigee parameters assigned to the track" ) ; 
    pt = -1e12; // return big value
  }
  else{  
    Amg::VectorX perigeeParams = perigee->parameters();
    pt = std::abs(sin(perigeeParams[Trk::theta])/perigeeParams[Trk::qOverP]);
    pt /= 1000.; // pt in GeV
  }
 
  return pt;
}

int InDetAlignTrackSelTool::nShared(const EventContext& ctx, const Trk::Track& track) const {
  ATH_MSG_DEBUG( "in nShared()" ) ;
  int nshared=0, nshpix, nshsct;
 
  xAOD::TrackParticle* trackPart = m_particleCreator->createParticle(ctx, track);
  uint8_t iSummaryValue(0); // Dummy counter to retrieve summary values
 
  if (not trackPart){
    ATH_MSG_ERROR("Could not get xAOD::TrackParticle");
    nshared = 1000;
  }
  else{
    nshpix = trackPart->summaryValue(iSummaryValue, xAOD::numberOfPixelSharedHits) ? iSummaryValue : 0;
    nshsct = trackPart->summaryValue(iSummaryValue, xAOD::numberOfSCTSharedHits) ? iSummaryValue : 0;
    //At condition nhpix == -1, the following bits of nhsct are known to be unset: 8-31.
    //The condition nhpix == -1 cannot be true.
    //At condition nhsct == -1, the following bits of nhsct are known to be unset: 8-31.
    //The condition nhsct == -1 cannot be true.
 
    nshared = nshpix + nshsct;
  }
  return nshared;
}

int InDetAlignTrackSelTool::nHoles(const EventContext& ctx, const Trk::Track& track) const {
  ATH_MSG_DEBUG( "in nHoles() " ) ;
  int nholes{}, nhpix{}, nhsct{};
 
  xAOD::TrackParticle* trackPart = m_particleCreator->createParticle(ctx, track);
  uint8_t iSummaryValue(0); // Dummy counter to retrieve summary values
 
  if (not trackPart){
    ATH_MSG_ERROR("Could not get xAOD::TrackParticle");
    nholes = 1000;
  }
  else{
    nhpix = trackPart->summaryValue(iSummaryValue, xAOD::numberOfPixelHoles) ? iSummaryValue : 0;
    nhsct = trackPart->summaryValue(iSummaryValue, xAOD::numberOfSCTHoles) ? iSummaryValue : 0;
    //At condition nhpix == -1, the following bits of nhsct are known to be unset: 8-31.
    //The condition nhpix == -1 cannot be true.
    //At condition nhsct == -1, the following bits of nhsct are known to be unset: 8-31.
    //The condition nhsct == -1 cannot be true.
    nholes =  nhpix + nhsct;
  }
  return nholes;
}

double InDetAlignTrackSelTool::chi2Prob(const Trk::Track& track) const {
  ATH_MSG_DEBUG( "in chi2Prob()" ) ;
  double chi2Prob=0.;
 
  // get fit quality and chi2 probability of track
  // chi2Prob = TMath::Prob(chi2,DoF) ROOT function
  const Trk::FitQuality* fitQual = track.fitQuality();
 
  if (fitQual==nullptr) {
    ATH_MSG_ERROR( "No fit quality assigned to the track" ) ; 
    chi2Prob = -1e12; // return big value
  }
  else {
    if (fitQual->chiSquared() > 0. && fitQual->numberDoF() > 0) {
      Genfun::CumulativeChiSquare probabilityFunction( fitQual->numberDoF() );
      chi2Prob = 1 - probabilityFunction( fitQual->chiSquared() );
    }
  }
 
  return chi2Prob;
}

int InDetAlignTrackSelTool::getStatus(const EventContext& ctx, const Trk::Track& track) const {
  ATH_MSG_DEBUG( "in getStatus()" ) ;
  int stat=1, nholes, nshared;
  double mom, pt, chi2prob;
 
  // momentum
  mom = Momentum(track);
  if (mom < m_minMomentum) {
    stat=0;
  }
 
  // transverse momentum
  pt = Pt(track);
  if (pt < m_minPt) {
    stat=0; 
  }
 
  // number of holes
  nholes = nHoles(ctx, track);
  if (nholes > m_maxHoles) {
    stat=0; 
  }
 
  // number of shared hits
  nshared = nShared(ctx, track);
  if (nshared > m_maxShared) {
    stat=0; 
  }
 
  // chi2 Probability
  chi2prob = chi2Prob(track);
  if (chi2prob < m_minChi2Prob) {
    stat=0;
  }
 
  ATH_MSG_DEBUG( " momentum(CLHEP::GeV)=" << mom 
         << " pt (CLHEP::GeV)=" << pt 
         << " nshared=" << nshared
         << " nholes=" <<  nholes 
         << " chi2Prob=" << chi2prob
         ) ;
 
  if(!stat)
    ATH_MSG_DEBUG( "Track not accepted" ) ;
  else
    ATH_MSG_DEBUG( "Track accepted" ) ;
 
  return stat;
}