InteractGeneral.cxx

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#include <cmath>
#include "lardata/RecoObjects/InteractGeneral.h"
#include "lardata/RecoObjects/SurfXYZPlane.h"
#include "cetlib_except/exception.h"

namespace trkf {

  InteractGeneral::InteractGeneral(double tcut) :
    Interactor(tcut),
    fInteract(tcut),
    fProp(-1., false)
  {}

  InteractGeneral::~InteractGeneral()
  {}

  bool InteractGeneral::noise(const KTrack& trk, double s, TrackError& noise_matrix) const
  {
    // Get track position and direction.

    double xyz[3];
    double mom[3];
    trk.getPosition(xyz);
    trk.getMomentum(mom);

    // Generate a SurfXYZPlane with origin at current track position, and
    // normal to current track direction.

    std::shared_ptr<Surface> psurf(new SurfXYZPlane(xyz[0], xyz[1], xyz[2],
                                                    mom[0], mom[1], mom[2]));

    // Propagate track to newly created surface (zero-distance propagation).

    TrackMatrix prop_matrix;
    KTrack temp_trk = trk;
    boost::optional<double> result = fProp.short_vec_prop(temp_trk, psurf, Propagator::UNKNOWN, 
                                                          false, &prop_matrix);

    // Return failure if propagation did not succeed.

    if(!result)
      return false;

    // Calculate noise on plane surface.

    TrackError plane_noise(5);
    fInteract.noise(temp_trk, s, plane_noise);

    // Transform noise matrix to original surface using inverse of propagation matrix.

    invert(prop_matrix);
    TrackMatrix temp = prod(plane_noise, trans(prop_matrix));
    TrackMatrix temp2 = prod(prop_matrix, temp);
    noise_matrix = ublas::symmetric_adaptor<TrackMatrix>(temp2);

    // Done (success).

    return true;
  }
} // end namespace trkf