TSCBLBuilderWithPropagator.cc

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#include "TrackingTools/PatternTools/interface/TSCBLBuilderWithPropagator.h"
#include "TrackingTools/GeomPropagators/interface/AnalyticalPropagator.h"
#include "TrackingTools/PatternTools/interface/TrajectoryExtrapolatorToLine.h"
#include "FWCore/MessageLogger/interface/MessageLogger.h"

using namespace std;

TSCBLBuilderWithPropagator::TSCBLBuilderWithPropagator(const MagneticField* field)
    : thePropagator(new AnalyticalPropagator(field, anyDirection)) {}

TSCBLBuilderWithPropagator::TSCBLBuilderWithPropagator(const Propagator& u) : thePropagator(u.clone()) {
  thePropagator->setPropagationDirection(anyDirection);
}

TrajectoryStateClosestToBeamLine TSCBLBuilderWithPropagator::operator()(const FreeTrajectoryState& originalFTS,
                                                                        const reco::BeamSpot& beamSpot) const {
  GlobalPoint bspos(beamSpot.position().x(), beamSpot.position().y(), beamSpot.position().z());
  GlobalVector bsvec(beamSpot.dxdz(), beamSpot.dydz(), 1.);
  Line bsline(bspos, bsvec);

  TrajectoryExtrapolatorToLine tetl;

  TrajectoryStateOnSurface tsosfinal = tetl.extrapolate(originalFTS, bsline, *thePropagator);

  if (!tsosfinal.isValid())
    return TrajectoryStateClosestToBeamLine();

  //Compute point on beamline of closest approach
  GlobalPoint tp = tsosfinal.globalPosition();  //position of trajectory closest approach
  GlobalVector hyp(
      tp.x() - bspos.x(), tp.y() - bspos.y(), tp.z() - bspos.z());  //difference between traj and beamline reference
  double l = bsline.direction().dot(hyp);                           //length along beamline away from reference point
  GlobalPoint closepoint = bspos + l * bsvec;

  //Get the free state and return the TSCBL
  const FreeTrajectoryState theFTS = *tsosfinal.freeState();
  return TrajectoryStateClosestToBeamLine(theFTS, closepoint, beamSpot);
}