TrackingRecHitPropagator.h

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#ifndef TrackingTools_TrackingRecHitPropagator_h
#define TrackingTools_TrackingRecHitPropagator_h

#include "DataFormats/TrackingRecHit/interface/InvalidTrackingRecHit.h"
#include "TrackingTools/TransientTrackingRecHit/interface/TransientTrackingRecHitBuilder.h"
#include "RecoTracker/TransientTrackingRecHit/interface/TkTransientTrackingRecHitBuilder.h"
#include "RecoTracker/TransientTrackingRecHit/interface/TkClonerImpl.h"

#include "TrackingTools/TransientTrackingRecHit/interface/TransientTrackingRecHit.h"
#include "TrackingTools/KalmanUpdators/interface/TrackingRecHitPropagator.h"
#include "TrackingTools/GeomPropagators/interface/AnalyticalPropagator.h"
#include "MagneticField/Engine/interface/MagneticField.h"
#include "TrackingTools/TrajectoryState/interface/TrajectoryStateOnSurface.h"
#include "FWCore/MessageLogger/interface/MessageLogger.h"

/* propagates the RecHit position from the original reference frame
   to the reference frame of another detector.
   Useful for algorithms like the DAF or the MTF    
*/

class TrackingRecHitPropagator {
public:
  TrackingRecHitPropagator(const MagneticField* magf) {
    thePropagator = new AnalyticalPropagator(magf, anyDirection, 1.6);
  };

  ~TrackingRecHitPropagator() { delete thePropagator; }

  template <class ResultingHit>
  TrackingRecHit::RecHitPointer project(const TrackingRecHit::ConstRecHitPointer hit,
                                        const GeomDet& det,
                                        const TrajectoryStateOnSurface ts,
                                        const TransientTrackingRecHitBuilder* builder) const {
    TkClonerImpl hc = static_cast<TkTransientTrackingRecHitBuilder const*>(builder)->cloner();

    //1) propagate the best possible track parameters to the surface of the hit you want to "move" using a AnalyticalPropagator ;
    //2) create LocalTrajectoryParameters with the local x,y of the hit and direction + momentum from the propagated track parameters;
    //3) create a LocalTrajectoryError matrix which is 0 except for the local x,y submatrix, which is filled with the hit errors;
    //4) create a TSOS from the result of 2) and 3) and propagate it to the reference surface;
    //5) create a new hit with the local x,y subspace of the result of 4)
    if (!ts.isValid())
      return std::make_shared<InvalidTrackingRecHit>(*hit->det(), TrackingRecHit::missing);
    //    LogTrace("SiTrackerMultiRecHitUpdator") << "the tsos is valid";
    //check if the ts lays or not on the destination surface and in case propagate it
    TrajectoryStateOnSurface propagated = ts;
    if (hit->surface() != &(ts.surface()))
      propagated = thePropagator->propagate(ts, *(hit->surface()));
    if (!propagated.isValid())
      return std::make_shared<InvalidTrackingRecHit>(*hit->det(), TrackingRecHit::missing);
    //    LogTrace("SiTrackerMultiRecHitUpdator") << "the propagate tsos is valid";
    //      LogTrace("SiTrackerMultiRecHitUpdator") << "Original: position: "<<hit->parameters()<<" error: "<<hit->parametersError()<<std::endl;
    //clone the original hit with this state
    TrackingRecHit::RecHitPointer updatedOriginal = hc.makeShared(hit, propagated);
    //      LogTrace("SiTrackerMultiRecHitUpdator") << "New: position: "<<updatedOriginal->parameters()<<" error: "<<updatedOriginal->parametersError()<<std::endl;

    //    LogTrace("SiTrackerMultiRecHitUpdator") << "rechit cloned";
    LocalTrajectoryParameters ltp(updatedOriginal->localPosition(), propagated.localMomentum(), propagated.charge());
    AlgebraicSymMatrix55 ltem;
    ltem(3, 3) = (updatedOriginal->parametersError())(1, 1);
    ltem(4, 4) = (updatedOriginal->parametersError())(2, 2);
    ltem(3, 4) = (updatedOriginal->parametersError())(1, 2);
    //      LogTrace("SiTrackerMultiRecHitUpdator") <<"The cov matrix: "<<ltem<<std::endl;
    LocalTrajectoryError lte(ltem);
    //      LogTrace("SiTrackerMultiRecHitUpdator") <<"Original cov matrix: "<<lte.matrix()<<std::endl;
    TrajectoryStateOnSurface hit_state(ltp, lte, propagated.surface(), propagated.magneticField());
    TrajectoryStateOnSurface projected_hit_state = thePropagator->propagate(hit_state, det.surface());
    if (!projected_hit_state.isValid())
      return std::make_shared<InvalidTrackingRecHit>(*hit->det(), TrackingRecHit::missing);
    LocalPoint p = projected_hit_state.localPosition();
    LocalError e = projected_hit_state.localError().positionError();
    //      LogTrace("SiTrackerMultiRecHitUpdator") << "position: "<<p<<" error: "<<e<<std::endl;
    //AlgebraicSymMatrix55 projm=projected_hit_state.localError().matrix();
    //      for(int i=0;i<5;i++){
    //      LogTrace("SiTrackerMultiRecHitUpdator") <<"cov matrix: "<<projm<<std::endl;
    //      }
    return ResultingHit::build(p, e, &det, updatedOriginal->det(), updatedOriginal, this);
  }

private:
  const AnalyticalPropagator* thePropagator;
};

#endif