/data/refman/pasoursint/CMSSW_5_2_7_hltpatch1/src/TrackingTools/KalmanUpdators/interface/TrackingRecHitPropagator.h

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#ifndef TrackingTools_TrackingRecHitPropagator_h
#define TrackingTools_TrackingRecHitPropagator_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 "TrackingTools/TransientTrackingRecHit/interface/InvalidTransientRecHit.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> TransientTrackingRecHit::RecHitPointer project(const TransientTrackingRecHit::ConstRecHitPointer hit,
                                                                                     const GeomDet& det,
                                                                                     const TrajectoryStateOnSurface ts) const{
        //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 InvalidTransientRecHit::build(hit->det());
          //      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 InvalidTransientRecHit::build(hit->det());    
                //        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
                TransientTrackingRecHit::RecHitPointer updatedOriginal = hit->clone(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 InvalidTransientRecHit::build(hit->det());   
                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