Geant4ePropagator.h

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#ifndef TrackPropagation_Geant4ePropagator_h
#define TrackPropagation_Geant4ePropagator_h

#include <memory>

//CMS includes
// - Propagator
#include "TrackingTools/GeomPropagators/interface/Propagator.h"

// - Geant4e
#include "G4ErrorPropagatorManager.hh"
#include "G4ErrorSurfaceTarget.hh"
#include "G4ErrorPropagatorData.hh"

class Geant4ePropagator: public Propagator {

public:
    Geant4ePropagator(const MagneticField* field = nullptr, std::string particleName =
            "mu", PropagationDirection dir = alongMomentum);

    ~Geant4ePropagator() override;

/*
    virtual TrajectoryStateOnSurface
    propagate(const FreeTrajectoryState& ftsStart, const Plane& pDest) const override;

    virtual TrajectoryStateOnSurface
    propagate(const FreeTrajectoryState& ftsStart, const Cylinder& cDest) const override;
*/
/*        
    virtual TrajectoryStateOnSurface
    propagate(const TrajectoryStateOnSurface& tsos, const Plane& plane) const override;

    virtual TrajectoryStateOnSurface
    propagate(const TrajectoryStateOnSurface& tsos, const Cylinder& cyl) const override;
*/
    std::pair<TrajectoryStateOnSurface, double>
    propagateWithPath(const FreeTrajectoryState&, const Plane&) const override;

    std::pair<TrajectoryStateOnSurface, double>
    propagateWithPath(const FreeTrajectoryState&, const Cylinder&) const override;

    std::pair<TrajectoryStateOnSurface, double>
    propagateWithPath(const TrajectoryStateOnSurface&, const Plane&) const override;

    std::pair<TrajectoryStateOnSurface, double>
    propagateWithPath(const TrajectoryStateOnSurface&, const Cylinder&) const override;

    Geant4ePropagator* clone() const override {
        return new Geant4ePropagator(*this);
    }

    const MagneticField* magneticField() const override {
        return theField;
    }

private:

    typedef std::pair<TrajectoryStateOnSurface, double> TsosPP;
    typedef std::pair< bool, std::shared_ptr< G4ErrorTarget > > ErrorTargetPair;

    //Magnetic field
    const MagneticField* theField;

    //Name of the particle whose properties will be used in the propagation
    std::string theParticleName;

    //The Geant4e manager. Does the real propagation
    G4ErrorPropagatorManager* theG4eManager;
    G4ErrorPropagatorData* theG4eData;

    // Transform a CMS Reco detector surface into a Geant4 Target for the error propagation
    template <class SurfaceType>
    ErrorTargetPair transformToG4SurfaceTarget( const SurfaceType& pDest, bool moveTargetToEndOfSurface ) const;

    // generates the Geant4 name for a particle from the
    // string stored in theParticleName ( set via constructor )
    // and the particle charge.
    // 'mu' as a basis for muon becomes 'mu+' or 'mu-', depening on the charge
    // This method only supports neutral and +/- 1e charges so far
    //
    // returns the generated string
    std::string generateParticleName ( int charge ) const;

    // flexible method which performs the actual propagation either for a plane or cylinder
    // surface type
    //
    // returns TSOS after the propagation and the path length
    template <class SurfaceType>
    std::pair<TrajectoryStateOnSurface, double>
    propagateGeneric(const FreeTrajectoryState& ftsStart, const SurfaceType& pDest) const;

    // saves the Geant4 propagation direction (Forward or Backward) in the provided variable
    // reference mode and returns true if the propagation direction could be set
    template <class SurfaceType>
    bool configurePropagation ( G4ErrorMode & mode, SurfaceType const& pDest,
                                GlobalPoint const& cmsInitPos,GlobalVector const& cmsInitMom ) const;

    // special case to determine the propagation direction if the CMS propagation direction 'anyDirection'
    // was set.
    // This method is called by configurePropagation and provides specific implementations for Plane
    // and Cylinder classes
    template <class SurfaceType>
    bool configureAnyPropagation ( G4ErrorMode & mode, SurfaceType const& pDest,
                                   GlobalPoint const& cmsInitPos,
                                   GlobalVector const& cmsInitMom  ) const;

    // Ensure Geant4 Error propagation is initialized, if not done so, yet
    // if the forceInit parameter is set to true, the initialization is performed,
    // even if already done before.
    // This can be necessary, when Geant4 needs to read in a new MagneticField object,
    // which changed during lumi section crossing
    void ensureGeant4eIsInitilized( bool forceInit ) const;

    // returns the name of the SurfaceType. Mostly for debug outputs
    template < class SurfaceType >
    std::string getSurfaceType ( SurfaceType const& surface) const;

    void debugReportPlaneSetup ( GlobalPoint const& posPlane, HepGeom::Point3D<double> const& surfPos,
                                 GlobalVector const& normalPlane, HepGeom::Normal3D<double> const& surfNorm,
                                 const Plane& pDest ) const;

    template <class SurfaceType>
    void  debugReportTrackState ( std::string const& currentContext, GlobalPoint const& cmsInitPos,
                                  CLHEP::Hep3Vector const& g4InitPos,
                                  GlobalVector const& cmsInitMom, CLHEP::Hep3Vector const& g4InitMom,
                                  const SurfaceType& pDest) const;
};

#endif