GhostTrackPrediction.h

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#ifndef RecoBTag_GhostTrackPrediction_h
#define RecoBTag_GhostTrackPrediction_h

#include <cmath>

#include <Math/SVector.h>
#include <Math/SMatrix.h>

#include "DataFormats/GeometryVector/interface/GlobalVector.h"
#include "DataFormats/GeometryVector/interface/GlobalPoint.h"
#include "DataFormats/GeometryCommonDetAlgo/interface/GlobalError.h"
#include "DataFormats/TrackReco/interface/TrackFwd.h"

class MagneticField;
class GlobalTrajectoryParameters;
class CurvilinearTrajectoryError;
class FreeTrajectoryState;

namespace reco {

  class GhostTrackPrediction {
  public:
    // z0, tIP, dz/dr, phi

    typedef ROOT::Math::SVector<double, 4> Vector;
    typedef ROOT::Math::SMatrix<double, 4, 4, ROOT::Math::MatRepSym<double, 4> > Error;
    typedef ROOT::Math::SMatrix<double, 6, 6, ROOT::Math::MatRepSym<double, 6> > CartesianError;

    GhostTrackPrediction() {}
    GhostTrackPrediction(const Vector &prediction, const Error &error) : prediction_(prediction), covariance_(error) {}

    GhostTrackPrediction(const GlobalPoint &priorPosition,
                         const GlobalError &priorError,
                         const GlobalVector &direction,
                         double coneRadius);

    GhostTrackPrediction(const GlobalPoint &priorPosition,
                         const GlobalError &priorError,
                         const GlobalVector &direction,
                         const GlobalError &directionError) {
      init(priorPosition, priorError, direction, directionError);
    }

    GhostTrackPrediction(const GlobalTrajectoryParameters &trajectory, const CurvilinearTrajectoryError &error);

    GhostTrackPrediction(const Track &track);

    double z() const { return prediction_[0]; }
    double ip() const { return prediction_[1]; }
    double cotTheta() const { return prediction_[2]; }
    double phi() const { return prediction_[3]; }

    double rho2() const { return cotTheta() * cotTheta() + 1.; }
    double rho() const { return std::sqrt(rho2()); }
    double sz() const { return z() / rho(); }
    double theta() const { return M_PI_2 - std::atan(cotTheta()); }
    double eta() const { return -std::log(rho() - cotTheta()); }

    const Vector &prediction() const { return prediction_; }
    const Error &covariance() const { return covariance_; }

    const GlobalPoint origin() const { return GlobalPoint(-std::sin(phi()) * ip(), std::cos(phi()) * ip(), z()); }
    const GlobalVector direction() const { return GlobalVector(std::cos(phi()), std::sin(phi()), cotTheta()); }

    double lambda(const GlobalPoint &point) const { return (point - origin()) * direction() / rho2(); }

    GlobalPoint position(double lambda = 0.) const { return origin() + lambda * direction(); }
    GlobalError positionError(double lambda = 0.) const;

    CartesianError cartesianError(double lambda = 0.) const;

    GlobalTrajectoryParameters globalTrajectory(const MagneticField *fieldProvider) const;
    CurvilinearTrajectoryError curvilinearError() const;

    FreeTrajectoryState fts(const MagneticField *fieldProvider) const;

    Track track(double ndof = 0., double chi2 = 0.) const;

  private:
    void init(const GlobalPoint &priorPosition,
              const GlobalError &priorError,
              const GlobalVector &direction,
              const GlobalError &directionError);

    Vector prediction_;
    Error covariance_;
  };

}  // namespace reco
#endif  // RecoBTag_GhostTrackPrediction_h