Template Function Acts::estimateTrackParamsFromSeed(const GeometryContext&, spacepoint_iterator_t, spacepoint_iterator_t, const Surface&, Vector3, ActsScalar, ActsScalar)

Function Documentation

template<typename spacepoint_iterator_t>
std::optional<BoundVector> Acts::estimateTrackParamsFromSeed(const GeometryContext &gctx, spacepoint_iterator_t spBegin, spacepoint_iterator_t spEnd, const Surface &surface, Vector3 bField, ActsScalar bFieldMin, ActsScalar mass = 139.57018 * UnitConstants::MeV)

Estimate the full track parameters from three space points.

This method is based on the conformal map transformation. It estimates the full bound track parameters, i.e. (loc0, loc1, phi, theta, q/p, t) at the bottom space point. The bottom space is assumed to be the first element in the range defined by the iterators. It must lie on the surface provided for the representation of the bound track parameters. The magnetic field (which might be along any direction) is also necessary for the momentum estimation.

It resembles the method used in ATLAS for the track parameters estimated from seed, i.e. the function InDet::SiTrackMaker_xk::getAtaPlane here: https://acode-browser.usatlas.bnl.gov/lxr/source/athena/InnerDetector/InDetRecTools/SiTrackMakerTool_xk/src/SiTrackMaker_xk.cxx

Return

optional bound parameters

Template Parameters

  • spacepoint_iterator_t: The type of space point iterator

Parameters

  • gctx: is the geometry context

  • spBegin: is the begin iterator for the space points

  • spEnd: is the end iterator for the space points

  • surface: is the surface of the bottom space point. The estimated bound track parameters will be represented also at this surface

  • bField: is the magnetic field vector

  • bFieldMin: is the minimum magnetic field required to trigger the estimation of q/pt

  • mass: is the estimated particle mass