TGC_ResidualPullCalculator.cxx

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
 
#include "TGC_ResidualPullCalculator.h"
 
#include "TrkRIO_OnTrack/RIO_OnTrack.h"
#include "MuonReadoutGeometry/TgcReadoutElement.h"
#include "MuonCompetingRIOsOnTrack/CompetingMuonClustersOnTrack.h"
#include "EventPrimitives/EventPrimitives.h"
 
//================ Initialisation =================================================
 
StatusCode Muon::TGC_ResidualPullCalculator::initialize()
{
  ATH_CHECK(m_idHelperSvc.retrieve());
  ATH_MSG_DEBUG ("initialize() successful in " << name());
  return StatusCode::SUCCESS;
}
 
//================ calculate residuals for TGC ==================================
std::array<double,5>
Muon::TGC_ResidualPullCalculator::residuals(
    const Trk::MeasurementBase* measurement,
    const Trk::TrackParameters* trkPar,
    const Trk::ResidualPull::ResidualType /*resType*/,
    const Trk::TrackState::MeasurementType) const {
  std::array<double,5> residuals{};
  const Trk::RIO_OnTrack* rot = dynamic_cast<const Trk::RIO_OnTrack*>(measurement);
  if (!rot) {
    const Muon::CompetingMuonClustersOnTrack* muonCompClusters =
      dynamic_cast<const Muon::CompetingMuonClustersOnTrack*>(measurement);
    if (muonCompClusters) rot = muonCompClusters->containedROTs().empty() ? nullptr : &muonCompClusters->rioOnTrack(0);
  }
  if (!trkPar || !rot) {
    if( !trkPar ) ATH_MSG_WARNING ("No TrackParameters, cannot calculate residual/pull ");
    if( !rot )    ATH_MSG_WARNING ("No ROT, cannot calculate residual/pull ");
    return residuals;
  }
  Identifier ID = rot->identify();
 
  if( m_idHelperSvc->isTgc(ID) ) {
 
    double sinAlpha = 0.0;
 
    bool isStrip = m_idHelperSvc->tgcIdHelper().isStrip(ID);
 
    // calculate residual
    if (isStrip) {
      // consistency check that Muon EDM is as expected
      if (measurement->localParameters().parameterKey() !=3) {
        ATH_MSG_WARNING ( "TGC ClusterOnTrack does not carry the expected "
                          << "LocalParameters structure!");
        return residuals;
      }
      // get orientation angle of strip to rotate back from local frame to strip
      const Amg::MatrixX &covmat=measurement->localCovariance();
      double v0=0.5*(covmat(0,0)+covmat(1,1)-sqrt((covmat(0,0)+covmat(1,1))*(covmat(0,0)+covmat(1,1))-
                            4*(covmat(0,0)*covmat(1,1)-covmat(0,1)*covmat(0,1))));
      double v1=0.5*(covmat(0,0)+covmat(1,1)+sqrt((covmat(0,0)+covmat(1,1))*(covmat(0,0)+covmat(1,1))-
                            4*(covmat(0,0)*covmat(1,1)-covmat(0,1)*covmat(0,1))));
      sinAlpha=std::sin(0.5*std::asin(2*covmat(0,1)/(v0-v1)));
 
      double cosAlpha = std::sqrt(1 - sinAlpha*sinAlpha);
 
      // Calculate Residual for hit: res = (vec(x_hit) - vec(x_track)) * vec(n_perpendicular)
      residuals[Trk::loc1] =
    (measurement->localParameters()[Trk::locX] - trkPar->parameters()[Trk::locX]) * cosAlpha
    + (measurement->localParameters()[Trk::locY] - trkPar->parameters()[Trk::locY]) * sinAlpha;
 
    } else {
      if (measurement->localParameters().parameterKey() != 1) {
        ATH_MSG_WARNING ("TGC ClusterOnTrack does not carry the expected "
                         << "LocalParameters structure!" );
        return residuals;
      } else {
        // convention to be interpreted by TrkValTools: 2nd coordinate codes orientation of TGC
        residuals[Trk::loc1] = measurement->localParameters()[Trk::loc1]
          - trkPar->parameters()[Trk::loc1];
      }
    }
  } else {
    ATH_MSG_DEBUG ( "Input problem measurement is not TGC." );
    return residuals;
  }
  return residuals;
}
 
//================ calculate residuals and pulls for TGC ==================================
std::optional<Trk::ResidualPull> Muon::TGC_ResidualPullCalculator::residualPull(
    const Trk::MeasurementBase* measurement,
    const Trk::TrackParameters* trkPar,
    const Trk::ResidualPull::ResidualType resType,
    const Trk::TrackState::MeasurementType) const {
 
  const Trk::RIO_OnTrack* rot = dynamic_cast<const Trk::RIO_OnTrack*>(measurement);
  if (!rot) {
    const Muon::CompetingMuonClustersOnTrack* muonCompClusters =
      dynamic_cast<const Muon::CompetingMuonClustersOnTrack*>(measurement);
    if (muonCompClusters) rot = muonCompClusters->containedROTs().empty() ? nullptr :
      muonCompClusters->containedROTs().front().get();
  }
  if (!trkPar || !rot) {
    if( !trkPar ) ATH_MSG_WARNING ("No TrackParameters, cannot calculate residual/pull ");
    if( !rot )    ATH_MSG_WARNING ("No ROT, cannot calculate residual/pull ");
    return std::nullopt;
  }
  Identifier ID = rot->identify();
 
  if( m_idHelperSvc->isTgc(ID) ) {
 
    // try to cast the track parameters to measured ones
    const AmgSymMatrix(5)* trkCov = trkPar->covariance();
    bool pullIsValid = (trkCov);
 
    double sinAlpha = 0.0;
 
    bool isStrip = m_idHelperSvc->tgcIdHelper().isStrip(ID);
 
    // calculate residual
    std::vector<double> residual(1);
    std::vector<double> pull(1);
    if (isStrip) {
      // consistency check that Muon EDM is as expected
      if (measurement->localParameters().parameterKey() !=3) {
        ATH_MSG_WARNING ( "TGC ClusterOnTrack does not carry the expected "
                          << "LocalParameters structure!");
        return std::nullopt;
      }
      // get orientation angle of strip to rotate back from local frame to strip
      const Amg::MatrixX &covmat=measurement->localCovariance();
      double v0=0.5*(covmat(0,0)+covmat(1,1)-sqrt((covmat(0,0)+covmat(1,1))*(covmat(0,0)+covmat(1,1))-
                            4*(covmat(0,0)*covmat(1,1)-covmat(0,1)*covmat(0,1))));
      double v1=0.5*(covmat(0,0)+covmat(1,1)+sqrt((covmat(0,0)+covmat(1,1))*(covmat(0,0)+covmat(1,1))-
                            4*(covmat(0,0)*covmat(1,1)-covmat(0,1)*covmat(0,1))));
      sinAlpha=std::sin(0.5*std::asin(2*covmat(0,1)/(v0-v1)));
 
      const MuonGM::TgcReadoutElement *ele =
        dynamic_cast<const MuonGM::TgcReadoutElement*>(rot->detectorElement());
      if (!ele) {
        ATH_MSG_WARNING ("Could not obtain TGC detEl from TGC ROT, this is a bug!" );
        return std::nullopt;
      }
 
      double cosAlpha = std::sqrt(1 - sinAlpha*sinAlpha);
 
      // Calculate Residual for hit: res = (vec(x_hit) - vec(x_track)) * vec(n_perpendicular)
      residual[Trk::loc1] =
    (measurement->localParameters()[Trk::locX] - trkPar->parameters()[Trk::locX]) * cosAlpha
    + (measurement->localParameters()[Trk::locY] - trkPar->parameters()[Trk::locY]) * sinAlpha;
 
      // Fill transformation matrix to transform covariance matrices
      Amg::MatrixX RotMat(2,2);
      RotMat(0,0) = cosAlpha;
      RotMat(0,1) = sinAlpha;
      RotMat(1,0) = -sinAlpha;
      RotMat(1,1) = cosAlpha;
      // get the covariance matrix of the ROT and rotate it by stereo angle
      Amg::MatrixX transformedROTCov = measurement->localCovariance().similarity(RotMat);
 
      if (pullIsValid) {
        // Get local error matrix for track to calc pull
        // Just use first local coordinates
        // and rotate by the stereo angle
        Amg::MatrixX subm = trkCov->block<2,2>(0,0);
        Amg::MatrixX transformedTrkCov = subm.similarity(RotMat);
        // calc pull now
        pull[Trk::loc1] = calcPull(residual[Trk::loc1],
                                   transformedROTCov(0,0),
                                   transformedTrkCov(0,0),
                                   resType);
      } else {
        pull[Trk::loc1] = calcPull(residual[Trk::loc1],
                                   transformedROTCov(0,0),
                                   0.,
                                   resType);
      }
 
    } else {
      if (measurement->localParameters().parameterKey() != 1) {
        ATH_MSG_WARNING ("TGC ClusterOnTrack does not carry the expected "
                         << "LocalParameters structure!" );
        return std::nullopt;
      } else {
        // convention to be interpreted by TrkValTools: 2nd coordinate codes orientation of TGC
        residual[Trk::loc1] = measurement->localParameters()[Trk::loc1]
          - trkPar->parameters()[Trk::loc1];
        // calculate pull
        if (pullIsValid)
          pull[Trk::loc1] = calcPull(residual[Trk::loc1],
                                     measurement->localCovariance()(Trk::loc1,Trk::loc1),
                                     (*trkCov)(Trk::loc1,Trk::loc1),
                                     resType);
        else
          pull[Trk::loc1] = calcPull(residual[Trk::loc1],
                                     measurement->localCovariance()(Trk::loc1,Trk::loc1),
                                     0,
                                     resType);
      }
    }
    // create the Trk::ResidualPull.
    ATH_MSG_VERBOSE ( "Calculating Pull for channel " << m_idHelperSvc->toString(ID) << " residual " << residual[Trk::loc1] << " pull " << pull[Trk::loc1] );
 
    return std::make_optional<Trk::ResidualPull>(std::move(residual), std::move(pull), pullIsValid, resType, 1, sinAlpha);
 
  } else {
    ATH_MSG_DEBUG ( "Input problem measurement is not TGC." );
    return std::nullopt;
  }
}

double Muon::TGC_ResidualPullCalculator::calcPull(
    const double residual,
    const double locMesCov,
    const double locTrkCov,
    const Trk::ResidualPull::ResidualType& resType ) const {
    if( locMesCov < 0 ) {
      ATH_MSG_DEBUG("Bad error " << locMesCov << "  " << locTrkCov << " using measured error ");
      return 0;
    }
    double ErrorSum;
    if (resType == Trk::ResidualPull::Unbiased) {
      if( locMesCov + locTrkCov > 0 ) ErrorSum = std::sqrt(locMesCov + locTrkCov);
      else{
    ATH_MSG_DEBUG("Bad error measurement " << locMesCov << "  from track " << locTrkCov << ", using measured error ");
        ErrorSum = std::sqrt(locMesCov);
      }
    } else if (resType == Trk::ResidualPull::Biased) {
        if ((locMesCov - locTrkCov) < 0.) {
            return 0;
        }
        ErrorSum = std::sqrt(locMesCov - locTrkCov);
    } else ErrorSum = std::sqrt(locMesCov);
    if (ErrorSum != 0) return residual/ErrorSum;
    return 0;
}