TrajectoryExtrapolatorToLine Class Reference

#include <TrajectoryExtrapolatorToLine.h>

Public Member Functions
TrajectoryStateOnSurface	extrapolate (const FreeTrajectoryState &fts, const Line &L, const Propagator &p) const
	extrapolation with user-supplied propagator More...

Detailed Description

Definition at line 8 of file TrajectoryExtrapolatorToLine.h.

Member Function Documentation

TrajectoryStateOnSurface TrajectoryExtrapolatorToLine::extrapolate	(	const FreeTrajectoryState &	fts,
		const Line &	L,
		const Propagator &	p
	)		const

extrapolation with user-supplied propagator

Definition at line 9 of file TrajectoryExtrapolatorToLine.cc.

References anyDirection, TtFullHadDaughter::B, Plane::build(), Propagator::clone(), Line::closerPointToLine(), FreeTrajectoryState::curvilinearError(), Line::distance(), HLT_2018_cff::distance, TrajectoryStateOnSurface::globalMomentum(), TrajectoryStateOnSurface::globalPosition(), TrajectoryStateOnSurface::isValid(), LogDebug, PV3DBase< T, PVType, FrameType >::mag(), AlCaHLTBitMon_ParallelJobs::p, FreeTrajectoryState::parameters(), makeMuonMisalignmentScenario::rot, Vector3DBase< T, FrameTag >::unit(), XX, AlignmentPI::YY, and AlignmentPI::ZZ.

Referenced by TSCBLBuilderWithPropagator::operator()().

                                                                                                        {
  DeepCopyPointerByClone<Propagator> p(aPropagator.clone());
  p->setPropagationDirection(anyDirection);

  FreeTrajectoryState fastFts(fts.parameters(), fts.curvilinearError());
  GlobalVector T1 = fastFts.momentum().unit();
  GlobalPoint T0 = fastFts.position();
  double distance = 9999999.9;
  double old_distance;
  int n_iter = 0;
  bool refining = true;

  LogDebug("TrajectoryExtrapolatorToLine") << "START REFINING";
  while (refining) {
    LogDebug("TrajectoryExtrapolatorToLine") << "Refining cycle...";
    // describe orientation of target surface on basis of track parameters
    n_iter++;
    Line T(T0, T1);
    GlobalPoint B = T.closerPointToLine(L);
    old_distance = distance;

    //create surface
    GlobalPoint BB = B + 0.3 * (T0 - B);
    Surface::PositionType pos(BB);
    GlobalVector XX(T1.y(), -T1.x(), 0.);
    GlobalVector YY(T1.cross(XX));
    Surface::RotationType rot(XX, YY);
    ReferenceCountingPointer<Plane> surface = Plane::build(pos, rot);
    LogDebug("TrajectoryExtrapolatorToLine") << "Current plane position: " << surface->toGlobal(LocalPoint(0., 0., 0.));
    LogDebug("TrajectoryExtrapolatorToLine") << "Current plane normal: " << surface->toGlobal(LocalVector(0, 0, 1));
    LogDebug("TrajectoryExtrapolatorToLine") << "Current momentum:     " << T1;

    // extrapolate fastFts to target surface
    TrajectoryStateOnSurface tsos = p->propagate(fastFts, *surface);

    if (!tsos.isValid()) {
      LogDebug("TrajectoryExtrapolatorToLine") << "TETL - extrapolation failed";
      return tsos;
    } else {
      T0 = tsos.globalPosition();
      T1 = tsos.globalMomentum().unit();
      GlobalVector D = L.distance(T0);
      distance = D.mag();
      if (fabs(old_distance - distance) < 0.000001) {
        refining = false;
      }
      if (old_distance - distance < 0.) {
        refining = false;
        LogDebug("TrajectoryExtrapolatorToLine") << "TETL- stop to skip loops";
      }
    }
  }
  //
  // Now propagate with errors and (not for the moment) perform rotation
  //
  // Origin of local system: point of closest approach on the line
  // (w.r.t. to tangent to helix at last iteration)
  //
  Line T(T0, T1);
  GlobalPoint origin(L.closerPointToLine(T));
  //
  // Axes of local system:
  //   x from line to helix at closest approach
  //   z along the helix
  //   y to complete right-handed system
  //
  GlobalVector ZZ(T1.unit());
  GlobalVector YY(ZZ.cross(T0 - origin).unit());
  GlobalVector XX(YY.cross(ZZ));
  Surface::RotationType rot(XX, YY, ZZ);
  ReferenceCountingPointer<Plane> surface = Plane::build(origin, rot);
  TrajectoryStateOnSurface tsos = p->propagate(fts, *surface);

  return tsos;
}