TRT_SegmentToTrackTool.cxx

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/*
  Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
*/
 
#include "TRT_SegmentToTrackTool/TRT_SegmentToTrackTool.h"
#include "TrkPseudoMeasurementOnTrack/PseudoMeasurementOnTrack.h"
#include "InDetRIO_OnTrack/TRT_DriftCircleOnTrack.h"
#include "InDetIdentifier/TRT_ID.h"
#include "TrkSurfaces/Surface.h"
 
#include <cmath>
 
using Amg::Vector3D;
using CLHEP::mm;
 
namespace {
   Amg::Vector2D project2D(const Amg::Vector3D &vec) {
      Amg::Vector2D tmp{vec[0],vec[1] };
      return tmp;
   }
}
namespace InDet {
 
  // Constructor with parameters:
  TRT_SegmentToTrackTool::TRT_SegmentToTrackTool(const std::string &type,
                                 const std::string &name,
                                 const IInterface *parent) :
    AthAlgTool(type,name,parent)
  {
    declareInterface<InDet::ITRT_SegmentToTrackTool>( this );
  }
 
  TRT_SegmentToTrackTool::~TRT_SegmentToTrackTool()
  = default;
 
 
  StatusCode TRT_SegmentToTrackTool::initialize() {
 
    ATH_CHECK( AthAlgTool::initialize() );
 
    ATH_CHECK(m_extrapolator.retrieve() );
 
    ATH_CHECK(m_fitterTool.retrieve(DisableTool{ !m_doRefit }));
    ATH_CHECK(m_assoTool.retrieve( DisableTool{m_assoTool.name().empty()} ));
    ATH_CHECK(m_trackSummaryTool.retrieve( DisableTool{m_trackSummaryTool.name().empty()} ));
 
    // Get the scoring tool
    ATH_CHECK( m_scoringTool.retrieve() );
 
    ATH_CHECK( detStore()->retrieve(m_trtId, "TRT_ID") );
    ATH_CHECK( m_fieldCacheCondObjInputKey.initialize());
 
    // Get output print level
    //
    ATH_MSG_DEBUG( *this );
 
    return StatusCode::SUCCESS;
 
  }
 
  StatusCode InDet::TRT_SegmentToTrackTool::finalize(){
    StatusCode sc = AthAlgTool::finalize();
    return sc;
  }
 
 
  // Dumps relevant information into the MsgStream
  MsgStream&  InDet::TRT_SegmentToTrackTool::dump( MsgStream& out ) const {
    out<<std::endl;
    return dumpconditions(out);
  }
 
  // Dumps conditions information into the MsgStream
 
  MsgStream& InDet::TRT_SegmentToTrackTool::dumpconditions( MsgStream& out ) const
  {
    int n = 65-m_fitterTool.type().size();
    std::string s1; for(int i=0; i<n; ++i) s1.append(" "); s1.append("|");
    n     = 65-m_assoTool.type().size();
    std::string s2; for(int i=0; i<n; ++i) s2.append(" "); s2.append("|");
    n     = 65-m_scoringTool.type().size();
    std::string s5; for(int i=0; i<n; ++i) s5.append(" "); s5.append("|");
 
 
    out<<std::endl
       <<"|----------------------------------------------------------------------"
       <<"-------------------|"<<std::endl;
    out<<"| Tool for final track refitting    | "<<m_fitterTool.type()   <<s1<<std::endl;
    out<<"| Tool for track scoring            | "<<m_scoringTool.type()  <<s5<<std::endl;
    out<<"| Association service               | "<<m_assoTool.type()     <<s2<<std::endl;
    out<<"|----------------------------------------------------------------------"
       <<"-------------------|";
    return out;
  }
 
 
  // Dumps event information into the MsgStream
  MsgStream& InDet::TRT_SegmentToTrackTool::dumpevent( MsgStream& out ) {
    return out;
  }
 
  // Dumps relevant information into the ostream
 
  std::ostream& InDet::TRT_SegmentToTrackTool::dump( std::ostream& out ) const
  {
    return out;
  }
 
 
  Trk::Track* TRT_SegmentToTrackTool::segToTrack(const EventContext& ctx, const Trk::TrackSegment& tS) const {
 
    ATH_MSG_DEBUG("Transforming the TRT segment into a track...");
 
    //
    // Get the track segment fit quality. If not there drop segment
    //
    if (!tS.fitQuality()) {
      ATH_MSG_DEBUG("Segment has no fit quality ! Discard...");
      return nullptr;
    }
    auto fq = tS.fitQuality()->uniqueClone();
 
    //
    // Get the track segment information about the initial track parameters
    //
    const AmgVector(5)& par = tS.localParameters();
    AmgSymMatrix(5) ep = AmgSymMatrix(5)(tS.localCovariance());
    const Trk::TrackParameters* segPar =
      tS.associatedSurface()
        .createUniqueTrackParameters(par[Trk::loc1],
                                     par[Trk::loc2],
                                     par[Trk::phi],
                                     par[Trk::theta],
                                     par[Trk::qOverP],
                                     std::move(ep))
        .release();
 
    if (segPar) {
      ATH_MSG_VERBOSE("Initial TRT Segment Parameters : " << (*segPar));
    } else {
      ATH_MSG_DEBUG("Could not get initial TRT segment parameters! ");
      // clean up
      return nullptr;
    }
 
    // --- create new track state on surface vector
    auto ntsos = std::make_unique<Trk::TrackStates>();
 
    //
    // if no refit, make it a perigee
    //
    if (!m_doRefit) {
 
      const Trk::TrackStateOnSurface* par_tsos = nullptr;
 
      // --- create surface at perigee
      Amg::Vector3D perigeePosition(0., 0., 0.);
      Trk::PerigeeSurface perigeeSurface(perigeePosition);
      // --- turn parameters into perigee...
      std::unique_ptr<Trk::TrackParameters> tmp =
        m_extrapolator->extrapolate(ctx, *segPar, perigeeSurface);
      std::unique_ptr<Trk::Perigee> perParm = nullptr;
      //pass ownership if of the right type
      if (tmp && tmp->associatedSurface().type() == Trk::SurfaceType::Perigee) {
        perParm.reset(static_cast<Trk::Perigee*>(tmp.release()));
      }
      if (perParm) {
        ATH_MSG_VERBOSE("Perigee version of Parameters : " << (*segPar));
      } else {
        ATH_MSG_DEBUG("Failed to build perigee parameters.Discard...");
        ntsos->clear();
        delete segPar;
        segPar = nullptr;
        return nullptr;
      }
 
      // now create a perigee TSOS
      std::bitset<Trk::TrackStateOnSurface::NumberOfTrackStateOnSurfaceTypes>
        typePattern;
      typePattern.set(Trk::TrackStateOnSurface::Perigee);
      par_tsos = new Trk::TrackStateOnSurface(
        nullptr, std::move(perParm), nullptr, typePattern);
      // push new TSOS into the list
      ntsos->push_back(par_tsos);
    }
 
    //
    // now loop over the TSOS and copy them in
    //
 
    // psuedo measurement information
    int npseudo = 0;
    double pseudotheta = 0;
    const Trk::MeasurementBase* pseudo = nullptr;
    // other measurement information
    const Trk::Surface *firstsurf = nullptr, *firstecsurf = nullptr,
                       *lastsurf = nullptr;
    const Trk::MeasurementBase* firstmeas = nullptr;
    // counters for barrel and endcap
    int nbarrel = 0, nendcap = 0;
    // some variables for endcaps
    std::vector<std::pair<double, double>> points;
    points.reserve(40);
    double oldphi = 0;
 
    const Trk::Surface *surf_zmin=nullptr;
    const Trk::Surface *surf_zmax=nullptr;
    int  meas_zmin_i=int(tS.numberOfMeasurementBases());
    int  meas_zmax_i=int(tS.numberOfMeasurementBases());
 
    // loop over the measurements in track segment (tS)
    for (int it = 0; it < int(tS.numberOfMeasurementBases()); it++) {
 
      // the track state on service we like to constuct ...
      const Trk::TrackStateOnSurface* seg_tsos = nullptr;
 
      // is this ROT a psuedo-measurement ?
      if (dynamic_cast<const Trk::PseudoMeasurementOnTrack*>(
            tS.measurement(it))) {
        // did we have a speudo-measurement before ?
        if (pseudo) {
          // get theta from pseudo measurements
          pseudotheta =
            std::atan2(tS.measurement(it)->associatedSurface().center().perp(),
                  tS.measurement(it)->associatedSurface().center().z());
        }
        // keep this pseudo measurement
        pseudo = tS.measurement(it);
        // update counter
        npseudo++;
 
        if (m_doRefit) {
          // refit means we can simply copy the state, otherwise we skip it
          seg_tsos =
            new Trk::TrackStateOnSurface(tS.measurement(it)->uniqueClone(), nullptr);
        }
 
      } else {
        //
        // normal measurement, not a pseudo measurement
        //
        // copy measurement
        seg_tsos =
          new Trk::TrackStateOnSurface(tS.measurement(it)->uniqueClone(), nullptr);
        //
        // --- following is for the hack below
        //
 
        // remember first measurement
        if (!firstmeas)
          firstmeas = tS.measurement(it);
        if (!firstsurf)
          firstsurf = &tS.measurement(it)->associatedSurface();
        // it is always the last one
        lastsurf = &tS.measurement(it)->associatedSurface();
 
        // detect endcap elemeents
        if (!m_trtId->is_barrel(tS.measurement(it)->associatedSurface().associatedDetectorElementIdentifier())) {
          // increase counter and keep some information
          nendcap++;
          if (!firstecsurf)
            firstecsurf = &tS.measurement(it)->associatedSurface();
 
          double tmpphi =
            tS.measurement(it)->associatedSurface().center().phi();
          if (!points.empty() &&
              std::abs(tmpphi - oldphi) > M_PI) { // correct for boundary at +/- pi
            if (tmpphi < 0)
              tmpphi += 2 * M_PI;
            else
              tmpphi -= 2 * M_PI;
          }
          // remember oldphi
          oldphi = tmpphi;
 
          if (!surf_zmax || std::abs(tS.measurement(it)->associatedSurface().center().z())>std::abs(surf_zmax->center().z())) {
             surf_zmax = &tS.measurement(it)->associatedSurface();
             meas_zmax_i = it;
          }
          if (!surf_zmin || std::abs(tS.measurement(it)->associatedSurface().center().z())<std::abs(surf_zmin->center().z())) {
             surf_zmin = &tS.measurement(it)->associatedSurface();
             meas_zmin_i = it;
          }
          // copy the points
          points.emplace_back(
            tS.measurement(it)->associatedSurface().center().z(), tmpphi);
 
        } else
          nbarrel++;
 
        //
        // --- end of hack stuff
        //
      }
 
      // push new TSOS into the list
      if (seg_tsos)
        ntsos->push_back(seg_tsos);
    }
 
    // Construct the new track
    Trk::TrackInfo info;
    info.setPatternRecognitionInfo(Trk::TrackInfo::TRTStandalone);
 
    // create new track candidate
    if (!m_doRefit) {
      return new Trk::Track(info, std::move(ntsos), std::move(fq));
    } else {
      //
      // ----------------------------- this is a horrible hack to make the
      // segments fittable
      //
 
      // in case of only 1 pseudo measurement, use the theta from it.
      if (npseudo == 1)
        pseudotheta = pseudo->localParameters()[Trk::theta];
 
      // we need new perigee parameters
      double myqoverp = 0, myphi = 0, myd0 = 0, myz0 = 0, mytheta = pseudotheta;
 
      if (nendcap < 4) {
        //
        // --- are we in the barrel mostly
        //
 
        // momentum
        myqoverp = par[4] * std::sin(pseudotheta) / std::sin(par[3]);
 
        // --- create surface at perigee
        Amg::Vector3D perigeePosition(0., 0., 0.);
        Trk::PerigeeSurface perigeeSurface(perigeePosition);
        // -- get perigee
        std::unique_ptr<const Trk::TrackParameters> tmp =
          m_extrapolator->extrapolate(ctx, *segPar, perigeeSurface);
        std::unique_ptr<const Trk::Perigee> tempper = nullptr;
        if (tmp && tmp->associatedSurface().type() == Trk::SurfaceType::Perigee) {
           tempper.reset(static_cast<const Trk::Perigee*>(tmp.release()));
        }
        if (!tempper) {
          ATH_MSG_DEBUG("Could not produce perigee");
          delete segPar;
          segPar = nullptr;
          return nullptr;
        }
 
        // keep some values
        myd0 = tempper->parameters()[Trk::d0];
        myphi = tempper->parameters()[Trk::phi0];
 
      } else {
        //
        // --- endcap or transition track
        //
 
        // get estimate of parameters
        double sx = 0, sy = 0, sxx = 0, sxy = 0, d = 0;
        float zmin = points.empty() ? 0 : points.begin()->first, zmax = 0;
        // loop over all points
 
        for (auto & point : points) {
          sx += point.first;
          sy += point.second;
          sxy += point.first * point.second;
          sxx += point.first * point.first;
          if (std::abs(point.first) > std::abs(zmax)) {
            zmax = point.first;
          }
          if (std::abs(point.first) < std::abs(zmin)) {
            zmin = point.first;
          }
        }
 
        if (std::abs(pseudotheta) < 1.e-6) {
          ATH_MSG_DEBUG("pseudomeasurements missing on the segment?");
 
          if (   meas_zmin_i < int(tS.numberOfMeasurementBases())
              && meas_zmax_i < int(tS.numberOfMeasurementBases())) {
             Amg::Vector3D meas_zmin = tS.measurement(meas_zmin_i)->globalPosition();
             Amg::Vector3D meas_zmax = tS.measurement(meas_zmax_i)->globalPosition();
             double diff_z (meas_zmax.z() - meas_zmin.z());
             if (std::abs(diff_z)>1e-6) {
                double diff_r( meas_zmax.perp() - meas_zmin.perp());
                pseudotheta = std::atan2(diff_r, diff_z);
                ATH_MSG_DEBUG("Initial pseudo theta is zero. Compute pseudo from inner- and outermost endcap measurements. delta R: " <<
                             meas_zmax.perp() << " - " << meas_zmin.perp()  << " = " << diff_r
                             << " , diff Z: " << meas_zmax.z() << " - " << meas_zmin.z()
                             << " = " << diff_z
                             << " " << pseudotheta);
             }
          }
 
          if (std::abs(pseudotheta) < 1.e-6) {
             constexpr std::array<float,2> boundary_r {644., 1004.};
             // true if track extends from endcap A to endcap C:
             bool is_across_sides=std::signbit(zmin)!=std::signbit(zmax);
             double r_path=is_across_sides ? 2 * boundary_r[1] :  boundary_r[1]-boundary_r[0];
             double r1 =0.;
             double r2 =0.;
             if (surf_zmin && surf_zmax) {
                bool is_reverse=std::abs(surf_zmin->center().z())>std::abs(surf_zmax->center().z());
                // use the innermost and outermost surfaces (defined by z-coordinate) to compute the
                // travel distance in R-direction assume that the outermost surface is always crossed
                // at the outermost radial position assume more over that the the innermost surface
                // is either crossed at the innermost or outermost position what ever leads to the
                // largest travel distance in r.
 
                std::array<const Trk::Surface *,2> boundary_surface{
                   is_reverse ? surf_zmax  : surf_zmin,
                   is_reverse ? surf_zmin : surf_zmax};
                // true if track goes from the outside to the insde :
                std::array<Amg::Vector2D,2> translation;
                std::array<Amg::Vector2D,2> height;
                for (unsigned int boundary_i=boundary_surface.size(); boundary_i-->0;) {
                   if (   boundary_surface[boundary_i]->type()          == Trk::SurfaceType::Line
                          && boundary_surface[boundary_i]->bounds().type() == Trk::SurfaceBounds::Cylinder) {
                      const Trk::CylinderBounds &
                         cylinder_bounds = dynamic_cast<const Trk::CylinderBounds &>(boundary_surface[boundary_i]->bounds());
                      height[boundary_i]= project2D( boundary_surface[boundary_i]->transform().rotation()
                                                     *  Amg::Vector3D(0,0, cylinder_bounds.halflengthZ()) );
                      translation[boundary_i]=project2D( boundary_surface[boundary_i]->transform().translation() );
                   }
                }
                r1 = (translation[1] + height[1]  - ( translation[0] + height[0])).perp();
                r2 = (translation[1] + height[1]  - ( translation[0] - height[0])).perp();
                r_path=std::max(r1,r2);
 
             }
             pseudotheta = std::atan2(r_path, zmax - zmin);
             ATH_MSG_DEBUG("Initial pseudo theta is zero. Pseudo theta from inner- and outermost surfaces. Deleta r " << r2 << " - " << r1 << " -> " << r_path
                          << " , delta Z " << zmax << " - " << zmin << " -> " << (zmax-zmin)
                          << " " << pseudotheta);
          }
        }
 
        // get q/p
        d = (points.size() * sxx - sx * sx);
        double dphidz = ((points.size() * sxy - sy * sx) / d);
        myqoverp = (std::abs(pseudotheta) > 1e-6)
                     ? -dphidz / (0.6 * std::tan(pseudotheta))
                     : 1000.;
 
        // some geometry stuff to estimate further paramters...
        double halfz = 200.;
        const Trk::CylinderBounds* cylb =
          dynamic_cast<const Trk::CylinderBounds*>(&firstsurf->bounds());
        if (!cylb)
          ATH_MSG_ERROR("Cast of bounds failed, should never happen");
        else
          halfz = cylb->halflengthZ();
        const Trk::CylinderBounds* cylb2 =
          dynamic_cast<const Trk::CylinderBounds*>(&lastsurf->bounds());
        double halfz2 = 200.;
        if (!cylb2)
          ATH_MSG_ERROR("Cast of bounds failed, should never happen");
        else
          halfz2 = cylb2->halflengthZ();
        Amg::Vector3D strawdir1 = -firstsurf->transform().rotation().col(2);
        Amg::Vector3D strawdir2 = -lastsurf->transform().rotation().col(2);
        Amg::Vector3D pos1;
        Amg::Vector3D pos2;
 
        // ME: this is hardcoding, not nice and should be fixed
        if (std::abs(lastsurf->center().z()) < 2650 * mm) {
          pos2 = lastsurf->center() + halfz2 * strawdir2;
          if (nbarrel == 0) {
            double dr = std::abs(std::tan(pseudotheta) * (lastsurf->center().z() -
                                                 firstsurf->center().z()));
            pos1 = firstsurf->center() + (halfz - dr) * strawdir1;
          } else {
            double dz = std::abs((pos2.perp() - firstsurf->center().perp()) /
                             std::tan(pseudotheta));
            if (pos2.z() > 0)
              dz = -dz;
            double z1 = pos2.z() + dz;
            pos1 = Amg::Vector3D(
              firstsurf->center().x(), firstsurf->center().y(), z1);
          }
        } else {
          double dr = std::abs(std::tan(pseudotheta) *
                           (lastsurf->center().z() - firstsurf->center().z()));
          pos2 = lastsurf->center() + (dr - halfz2) * strawdir2;
          pos1 = firstsurf->center() - halfz * strawdir1;
        }
 
        // ME: I don't understand this yet, why is this done only if barrel ==
        // 0, while above this nendcap < 4 ?
        if (nbarrel == 0 &&
            std::abs(std::tan(pseudotheta) * (firstsurf->center().z() -
                                         lastsurf->center().z())) < 250 * mm &&
            std::abs(firstsurf->center().z()) > 1000 * mm) {
 
          // ME: wow this is hacking the vector ...
          const Trk::MeasurementBase* firstmeas =
            (**ntsos->begin()).measurementOnTrack();
          Amg::MatrixX newcov(2, 2);
          newcov.setZero();
          newcov(0, 0) = (firstmeas->localCovariance())(0, 0);
          newcov(1, 1) = (myqoverp != 0) ? .0001 * myqoverp * myqoverp : 1.e-8;
          Trk::LocalParameters newpar(std::make_pair(0, Trk::locZ),
                                      std::make_pair(myqoverp, Trk::qOverP));
          auto newpseudo =
            std::make_unique<Trk::PseudoMeasurementOnTrack>(
              std::move(newpar),
              std::move(newcov),
              firstmeas->associatedSurface());
          // hack replace first measurement with pseudomeasurement
          ntsos->erase(ntsos->begin());
          ntsos->insert(ntsos->begin(),
                        new Trk::TrackStateOnSurface(std::move(newpseudo), nullptr));
        }
 
        Amg::Vector3D field1;
 
        MagField::AtlasFieldCache fieldCache;
 
        // Get field cache object
        SG::ReadCondHandle<AtlasFieldCacheCondObj> readHandle{
          m_fieldCacheCondObjInputKey, ctx
        };
        const AtlasFieldCacheCondObj* fieldCondObj{ *readHandle };
        if (fieldCondObj == nullptr) {
          ATH_MSG_ERROR(
            "segToTrack: Failed to retrieve AtlasFieldCacheCondObj with key "
            << m_fieldCacheCondObjInputKey.key());
          return nullptr;
        }
        fieldCondObj->getInitializedCache(fieldCache);
 
        //   MT version uses cache
        fieldCache.getField(Amg::Vector3D(.5 * (pos1 + pos2)).data(),
                            field1.data());
 
        field1 *= m_fieldUnitConversion; // field in Tesla
 
        double phideflection =
          -.3 * (pos2 - pos1).perp() * field1.z() * myqoverp / std::sin(pseudotheta);
        double precisephi = (nbarrel == 0)
                              ? (pos2 - pos1).phi() - .5 * phideflection
                              : (pos2 - pos1).phi() + .5 * phideflection;
        double radius = (myqoverp != 0. && field1.z() != 0.)
                          ? -std::sin(pseudotheta) / (.3 * field1.z() * myqoverp)
                          : 1.e6;
        double precisetheta =
          (myqoverp != 0.)
            ? std::atan2(std::abs(radius * phideflection), pos2.z() - pos1.z())
            : pseudotheta;
        if (precisetheta < 0)
          precisetheta += M_PI;
        if (precisephi < -M_PI)
          precisephi += 2 * M_PI;
        if (precisephi > M_PI)
          precisephi -= 2 * M_PI;
 
        // now extrapolate backwards from the first surface to get starting
        // parameters
        const Trk::StraightLineSurface* surfforpar = nullptr;
        if (nbarrel == 0)
          surfforpar = dynamic_cast<const Trk::StraightLineSurface*>(firstsurf);
        else
          surfforpar = dynamic_cast<const Trk::StraightLineSurface*>(lastsurf);
        if (!surfforpar)
          ATH_MSG_ERROR("Cast of surface failed, should never happen");
 
        Trk::AtaStraightLine ataline(((nbarrel == 0) ? pos1 : pos2),
                                     precisephi,
                                     precisetheta,
                                     myqoverp,
                                     *surfforpar);
        Trk::PerigeeSurface persurf;
        const Trk::TrackParameters* extrappar =
          m_extrapolator->extrapolateDirectly(ctx, ataline, persurf).release();
 
        // now get parameters
        if (extrappar) {
          if (nendcap >= 4) {
            myphi = extrappar->parameters()[Trk::phi0];
            myd0 = extrappar->parameters()[Trk::d0];
          }
 
          // construct theta again
          double z0 = extrappar->parameters()[Trk::z0];
          if (nbarrel == 0)
            mytheta = std::atan(std::tan(extrappar->parameters()[Trk::theta]) *
                           std::abs((z0 - pos1.z()) / pos1.z()));
          else
            mytheta = std::atan(std::tan(extrappar->parameters()[Trk::theta]) *
                           std::abs((z0 - pos2.z()) / pos2.z()));
 
          if (mytheta < 0)
            mytheta += M_PI;
 
          delete extrappar;
          extrappar = nullptr;
        }
      }
      while (myphi > M_PI)
        myphi -= 2 * M_PI;
      while (myphi < -M_PI)
        myphi += 2 * M_PI;
 
      double P[5] = { myd0, myz0, myphi, mytheta, myqoverp };
 
      // create perigee TSOS and add as first (!) TSOS
 
      auto per =
        std::make_unique<Trk::Perigee>(P[0], P[1], P[2], P[3], P[4], Trk::PerigeeSurface());
      std::bitset<Trk::TrackStateOnSurface::NumberOfTrackStateOnSurfaceTypes>
        typePattern;
      typePattern.set(Trk::TrackStateOnSurface::Perigee);
      Trk::TrackStateOnSurface* seg_tsos = new Trk::TrackStateOnSurface(
        nullptr, std::move(per), nullptr, typePattern);
      ntsos->insert(ntsos->begin(), seg_tsos);
 
      //
      // ------------------------------------------------------- now refit the
      // track
      //
 
      Trk::Track newTrack (info, std::move(ntsos), std::move(fq));
      Trk::Track* fitTrack =
        m_fitterTool->fit(ctx,newTrack, true, Trk::nonInteracting).release();
 
      // cleanup
      if (segPar) {
        delete segPar;
        segPar = nullptr;
      }
 
      if (!fitTrack) {
        ATH_MSG_DEBUG("Refit of TRT track segment failed!");
        return nullptr;
      }
 
      //
      // -------------------------------------- hack the covarinace back to
      // something reasonable
      //
      const Trk::TrackParameters* firstmeaspar = nullptr;
      DataVector<const Trk::TrackParameters>::const_iterator parit =
        fitTrack->trackParameters()->begin();
      do {
        // skip pesudo measurements on perigee
        if ((*parit)->covariance() &&
            ((*parit)->associatedSurface() == tS.associatedSurface()))
          firstmeaspar = *parit;
        ++parit;
      } while (firstmeaspar == nullptr &&
               parit != fitTrack->trackParameters()->end());
 
      // Create new perigee starting from the modified first measurement that
      // has a more reasonable covariance matrix
      // const Trk::Perigee* perTrack=dynamic_cast<const
      // Trk::Perigee*>(fitTrack->perigeeParameters());
      const Trk::Perigee* perTrack = fitTrack->perigeeParameters();
 
      if (!perTrack || !perTrack->covariance()) {
        ATH_MSG_ERROR("Cast of perigee fails, should never happen !");
        return nullptr;
      } else {
        ATH_MSG_VERBOSE ("Perigee after refit with fudges to make it converge : " << (*perTrack) );
 
    if(firstmeaspar && firstmeaspar->position().perp()<2000*mm && std::abs(firstmeaspar->position().z())<3000*mm){
 
      // Modify first measurement so that it has reasonable errors on z and theta
      AmgSymMatrix(5) fcovmat = AmgSymMatrix(5)(*(firstmeaspar->covariance()));
      // factors by which we like to scale the cov, this takes the original segment errors into account
      double scaleZ     = std::sqrt(tS.localCovariance()(1,1))/std::sqrt( (fcovmat)(1,1));
      double scaleTheta = std::sqrt(tS.localCovariance()(3,3))/std::sqrt( (fcovmat)(3,3));
      // now do it
      fcovmat(1,0)=scaleZ*((fcovmat)(1,0));
      fcovmat(0,1) = (fcovmat)(1,0);
      fcovmat(1,1)=tS.localCovariance()(1,1);
      fcovmat(2,1)=scaleZ*((fcovmat)(2,1));
      fcovmat(1,2) = (fcovmat)(2,1);
      fcovmat(3,1)=scaleZ*scaleTheta*((fcovmat)(3,1));
      fcovmat(1,3) = (fcovmat)(3,1);
      fcovmat(4,1)=scaleZ*((fcovmat)(4,1));
      fcovmat(1,4) = (fcovmat)(4,1);
      fcovmat(3,0)=scaleTheta*((fcovmat)(3,0));
      fcovmat(0,3) = (fcovmat)(3,0);
      fcovmat(3,2)=scaleTheta*((fcovmat)(3,2));
      fcovmat(2,3) = (fcovmat)(3,2);
      fcovmat(3,3)=tS.localCovariance()(3,3);
      fcovmat(4,3)=scaleTheta*((fcovmat)(4,3));
      fcovmat(3,4) = (fcovmat)(4,3);
 
      // const Amg::VectorX& par = firstmeaspar->parameters();
      const AmgVector(5)& par = firstmeaspar->parameters();
          const Trk::TrackParameters* updatedPars =
            firstmeaspar->associatedSurface().createUniqueTrackParameters(
              par[Trk::loc1],
              par[Trk::loc2],
              par[Trk::phi],
              par[Trk::theta],
              par[Trk::qOverP],
              std::move(fcovmat)).release();
 
          // now take parameters at first measurement and exptrapolate to perigee
          const Trk::TrackParameters* newperpar =
            m_extrapolator->extrapolate(ctx,
                                        *updatedPars,
                                        perTrack->associatedSurface(),
                                        Trk::anyDirection,
                                        false,
                                        Trk::nonInteracting).release();
          delete updatedPars; updatedPars = nullptr;
 
      if (!newperpar || !newperpar->covariance()) {
        ATH_MSG_WARNING ("Can not hack perigee parameters, extrapolation failed");
        delete newperpar; newperpar = nullptr;
      } else {
        // this is a HACK !!!
            // perTrack is owned by fitTrack which is not const here
            // thus the const-ness is only removed from somthting which is not strictly const here.
        AmgSymMatrix(5)& errmat ATLAS_THREAD_SAFE = const_cast<AmgSymMatrix(5)&>(*perTrack->covariance());
        // overwrite cov in perTrack
        errmat = *newperpar->covariance();
        delete newperpar; newperpar = nullptr;
        // check that new cov makes sense !
        const AmgSymMatrix(5)& CM = *perTrack->covariance();
        if( CM(1,1)==0.||CM(3,3)==0. ) {
          ATH_MSG_DEBUG ("Hacked perigee covariance is CRAP, reject track");
          delete fitTrack; return nullptr;
        } else {
          ATH_MSG_VERBOSE ("Perigee after fit with scaled covariance matrix : " << *perTrack);
        }
      }
    }
      }
      // return fitted track
      return fitTrack;
    }
  }
 
 
  bool TRT_SegmentToTrackTool::segIsUsed(const Trk::TrackSegment& tS,
                                         const Trk::PRDtoTrackMap *prd_to_track_map) const {
 
    ATH_MSG_DEBUG ("Checking whether the TRT segment has already been used...");
 
    // some counters to be handled
    int nShared = 0;  // Shared drift circles in segment
    int nHits   = 0;  // Number of TRT measurements
 
    if (m_assoTool.isEnabled()&& !prd_to_track_map) ATH_MSG_ERROR("PRDtoTrackMap to be used but not provided by the client");
    // loop over the track states
    for(int it=0; it<int(tS.numberOfMeasurementBases()); ++it){
 
      // remove pseudo measurements
      if ( dynamic_cast<const Trk::PseudoMeasurementOnTrack*>(tS.measurement(it)) )
        continue;
 
      // get the measurment
      const InDet::TRT_DriftCircleOnTrack* trtcircle = dynamic_cast<const InDet::TRT_DriftCircleOnTrack*>(tS.measurement(it));
      if (!trtcircle) continue;
 
      // get PRD measurement
      const InDet::TRT_DriftCircle* RawDataClus=dynamic_cast<const InDet::TRT_DriftCircle*>(trtcircle->prepRawData());
      if(!RawDataClus) continue;
 
      // count up number of hits
      nHits++;
 
      if(m_assoTool.isEnabled() && prd_to_track_map && prd_to_track_map->isUsed(*RawDataClus)) nShared++;
    }
 
    if(nShared >= int(m_sharedFrac * nHits)) {
      ATH_MSG_DEBUG ("Too many shared hits.Will drop the TRT segment");
      return true;
    } else {
      return false;
    }
 
 
  }
 
  bool TRT_SegmentToTrackTool::toLower(const Trk::TrackSegment& tS) const {
 
    ATH_MSG_DEBUG ("Try to recover low TRT DC segments in crack...");
 
    // counters
    int nEC = 0; int nBRL = 0; int firstWheel = -999; int lastLayer = -999;
 
    // loop over the track states
    for(int it=0; it<int(tS.numberOfMeasurementBases()); ++it){
 
      //test if it is a pseudo measurement
      if ( dynamic_cast<const Trk::PseudoMeasurementOnTrack*>(tS.measurement(it)) )
    continue;
 
      // get measurement
      const InDet::TRT_DriftCircleOnTrack* trtcircle = dynamic_cast<const InDet::TRT_DriftCircleOnTrack*>(tS.measurement(it));
      if(!trtcircle) continue;
 
      // get identifier
      Identifier id = trtcircle->detectorElement()->identify();
      // barrel or endcap
      int isB = m_trtId->barrel_ec(id);
      if      (isB==2 || isB==-2) {
    nEC++;
    if(nEC == 1)
      firstWheel = m_trtId->layer_or_wheel(id);
      }
      else if (isB==1 || isB==-1) {
    nBRL++;
    lastLayer  = m_trtId->layer_or_wheel(id);
      }
 
    }
 
    // now the logic
    return (nEC>0  && nBRL>0) ||
 
       (nEC==0 && nBRL>0  && lastLayer<2) ||
 
       (nEC>0  && nBRL==0 && (firstWheel>10 || firstWheel<2));
 
  }
 
  void TRT_SegmentToTrackTool::addNewTrack(Trk::Track* trk, ITRT_SegmentToTrackTool::EventData &event_data) const {
    // @TODO avoid non const member m_trackScoreTrackMap
    ATH_MSG_DEBUG ("Add track to the scoring multimap...");
    //Score the track under investigation
    Trk::TrackScore score = Trk::TrackScore(0);
    bool passBasicSelections = m_scoringTool->passBasicSelections(*trk);
    if(passBasicSelections){
      if (m_trackSummaryTool.isEnabled()) {
    m_trackSummaryTool->computeAndReplaceTrackSummary(*trk,
                              m_suppressHoleSearch);
      }
      score = m_scoringTool->score(*trk);
    }
    ATH_MSG_DEBUG ("TRT-only: score is " << score);
 
    if (score==0) {
      // statistics...
      ATH_MSG_DEBUG ("Track score is zero, reject it");
      event_data.m_counter[ITRT_SegmentToTrackTool::EventData::knTrkScoreZero]++;
      // clean up
      delete trk;
    } else {
      // add track to map, map is sorted small to big !
      event_data.m_trackScores.emplace_back(-score, trk );
    }
 
 
  }
 
 
  TrackCollection* TRT_SegmentToTrackTool::resolveTracks(const Trk::PRDtoTrackMap *prd_to_track_map_in,
                                                          ITRT_SegmentToTrackTool::EventData &event_data) const {
 
    ATH_MSG_DEBUG ("Resolving the TRT tracks in score map...");
 
 
    std::unique_ptr<Trk::PRDtoTrackMap> prd_to_track_map;
    if (m_assoTool.isEnabled()) {
      prd_to_track_map=m_assoTool->createPRDtoTrackMap();
      if (prd_to_track_map_in) {
        *prd_to_track_map = *prd_to_track_map_in;
      }
    }
 
    //final copy - ownership is passed out of algorithm
    std::unique_ptr<TrackCollection> final_tracks = std::make_unique<TrackCollection>();
    final_tracks->reserve( event_data.m_trackScores.size());
    std::stable_sort(event_data.m_trackScores.begin(),
                     event_data.m_trackScores.end(),
                     []( const std::pair< Trk::TrackScore, Trk::Track* > &a,
                         const std::pair< Trk::TrackScore, Trk::Track* > &b)
                     {  return a.first < b.first; });
 
    for (std::pair< Trk::TrackScore, Trk::Track* > &track_score : event_data.m_trackScores) {
 
      ATH_MSG_DEBUG ("--- Trying next track "<<track_score.second<<"\t with score "<<-track_score.first);
 
      // some counters to be handled
      int nShared = 0;  // Shared drift circles in segment
      int nHits   = 0;  // Number of TRT measurements
 
      // get vector of TSOS
      const Trk::TrackStates* tsos = (track_score.second)->trackStateOnSurfaces();
 
      // loop over vector of TSOS
      for ( const Trk::TrackStateOnSurface *a_tsos : *tsos) {
 
        // get measurment from TSOS
        const Trk::MeasurementBase* meas = a_tsos->measurementOnTrack();
        if (!meas)
          continue;
 
        // make sure it is a TRT_DC and not a pseudo measurement
        const InDet::TRT_DriftCircleOnTrack* rot =
            dynamic_cast<const InDet::TRT_DriftCircleOnTrack*>(meas);
        if (!rot)
          continue;
 
        // get to the PRD object
        const InDet::TRT_DriftCircle* RawDataClus =
            dynamic_cast<const InDet::TRT_DriftCircle*>(rot->prepRawData());
        if (!RawDataClus)
          continue;
 
        // count up number of hits
        nHits++;
 
        // count up number of shared hits
        if (m_assoTool.isEnabled() && prd_to_track_map->isUsed(*RawDataClus))
          nShared++;
      }
 
      ATH_MSG_DEBUG ("TRT-only has " << nHits << " hits and " << nShared << " of them are shared");
 
      // cut on the number of shared hits with the max fraction
      if(nShared >=  int(m_sharedFrac * nHits)) {
         // statistics
         event_data.m_counter[ITRT_SegmentToTrackTool::EventData::knTrkSegUsed]++;
         ATH_MSG_DEBUG ("Too many shared hits, remove it !");
         delete track_score.second;
         continue;
      }
 
      // ok, this seems like a useful track
      final_tracks->push_back(track_score.second);
 
      event_data.m_counter[ITRT_SegmentToTrackTool::EventData::knTRTTrk]++;
      ATH_MSG_DEBUG ("TRT-only is accepted");
 
      //Register the track with the association tool
      if(m_assoTool.isEnabled()) {
        if(m_assoTool->addPRDs(*prd_to_track_map,*(track_score.second)).isFailure()) {
      ATH_MSG_WARNING ("addPRDs() failed!");
    }
      }
 
    }
 
    return final_tracks.release();
 
  }
 
}