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TrajectoryStateClosestToPoint.h

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#ifndef TrajectoryStateClosestToPoint_H
#define TrajectoryStateClosestToPoint_H

#include "TrackingTools/TrajectoryState/interface/TrajectoryStateOnSurface.h"
#include "TrackingTools/TrajectoryState/interface/FreeTrajectoryState.h"
#include "TrackingTools/TrajectoryParametrization/interface/PerigeeTrajectoryParameters.h"
#include "TrackingTools/TrajectoryParametrization/interface/PerigeeTrajectoryError.h"
#include "TrackingTools/TrajectoryState/interface/PerigeeConversions.h"
#include "TrackingTools/TrajectoryParametrization/interface/TrajectoryStateExceptions.h"

class TrajectoryStateClosestToPoint
{
  typedef TrajectoryStateOnSurface      TSOS;
  typedef FreeTrajectoryState           FTS;

public:

  TrajectoryStateClosestToPoint():
    theFTSavailable(false), errorIsAvailable(false) {}

  TrajectoryStateClosestToPoint(const PerigeeTrajectoryParameters& perigeeParameters, double pt,
                                const GlobalPoint& referencePoint, const MagneticField* field);

  TrajectoryStateClosestToPoint(const PerigeeTrajectoryParameters& perigeeParameters, double pt,
    const PerigeeTrajectoryError& perigeeError, const GlobalPoint& referencePoint,
    const MagneticField* field);


  const GlobalPoint referencePoint() const {
    return theRefPoint;
  }


  const PerigeeTrajectoryParameters & perigeeParameters() const {
    return theParameters;
  }

  double pt() const { return thePt; }

  const PerigeeTrajectoryError & perigeeError() const {
    if (!errorIsAvailable) throw TrajectoryStateException(
      "TrajectoryStateClosestToPoint: attempt to access errors when none available");
    return thePerigeeError;
  }

  GlobalPoint position() const {
    return perigeeConversions.positionFromPerigee(theParameters, theRefPoint);
  }


  GlobalVector momentum() const {
    return perigeeConversions.momentumFromPerigee(theParameters, thePt, theRefPoint);
  }


  TrackCharge charge() const {
    return theParameters.charge();
  }


  const FreeTrajectoryState & theState() const {
    if (!theFTSavailable) calculateFTS();
    return theFTS;
  }


  bool hasError() const {
    return errorIsAvailable;
  }


private:

  friend class TrajectoryStateClosestToPointBuilder;
  friend class PerigeeConversions;

  TrajectoryStateClosestToPoint(const FTS& originalFTS, const GlobalPoint& referencePoint);

  void calculateFTS() const;

  const MagneticField* theField;

  mutable FTS theFTS;
  mutable bool theFTSavailable;
  
  GlobalPoint theRefPoint;
  PerigeeTrajectoryParameters theParameters;
  double thePt;
  PerigeeTrajectoryError thePerigeeError;
  bool errorIsAvailable;
  PerigeeConversions perigeeConversions;
  
};
#endif

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