TrackCovarianceDecoratorAlg.cxx

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
 
#include "TrackingDecorAlgorithms/TrackCovarianceDecoratorAlg.h"
 
#include "StoreGate/WriteDecorHandle.h"
 
#include <cmath>
 
 
namespace TrackingDecorAlgorithms {
 
  TrackCovarianceDecoratorAlg::TrackCovarianceDecoratorAlg(
    const std::string& name, ISvcLocator* loc)
    : AthReentrantAlgorithm(name, loc) {}
 
  StatusCode TrackCovarianceDecoratorAlg::initialize() {
    ATH_MSG_INFO("Initializing " << name() << "...");
 
    ATH_CHECK(m_trackContainerKey.initialize());
    ATH_CHECK(m_dec_phiUncertainty.initialize());
    ATH_CHECK(m_dec_thetaUncertainty.initialize());
    ATH_CHECK(m_dec_qOverPUncertainty.initialize());
 
    return StatusCode::SUCCESS;
  }
 
  StatusCode TrackCovarianceDecoratorAlg::execute(
    const EventContext& ctx) const
  {
    SG::ReadHandle<xAOD::TrackParticleContainer> tracks(
      m_trackContainerKey, ctx);
    ATH_CHECK(tracks.isValid());
 
    using TPC = xAOD::TrackParticleContainer;
    SG::WriteDecorHandle<TPC, float> dec_phi(m_dec_phiUncertainty, ctx);
    SG::WriteDecorHandle<TPC, float> dec_theta(m_dec_thetaUncertainty, ctx);
    SG::WriteDecorHandle<TPC, float> dec_qOverP(m_dec_qOverPUncertainty, ctx);
 
    for (const xAOD::TrackParticle* trk : *tracks) {
      const auto& diag = trk->definingParametersCovMatrixDiagVec();
      dec_phi(*trk) = std::sqrt(diag.at(2));
      dec_theta(*trk) = std::sqrt(diag.at(3));
      dec_qOverP(*trk) = std::sqrt(diag.at(4));
    }
 
    return StatusCode::SUCCESS;
  }
 
}