Acts::HelicalTrackLinearizer Class Reference

Linearizes the track parameters at the PCA to a user-provided point (linPoint). More...

#include <Acts/Vertexing/HelicalTrackLinearizer.hpp>

Classes
struct	Config
	Configuration struct. More...

Public Member Functions
	HelicalTrackLinearizer (const Config &config, std::unique_ptr< const Logger > _logger=getDefaultLogger("HelTrkLinProp", Logging::INFO))
	Constructor.
Result< LinearizedTrack >	linearizeTrack (const BoundTrackParameters &params, double linPointTime, const Surface &perigeeSurface, const Acts::GeometryContext &gctx, const Acts::MagneticFieldContext &mctx, MagneticFieldProvider::Cache &fieldCache) const
	Function that linearizes BoundTrackParameters at the PCA to a given Perigee surface.

Detailed Description

Linearizes the track parameters at the PCA to a user-provided point (linPoint).

The track parameters are written as a function of the global PCA position and the momentum of the particle at the PCA. The linearization then reads (see Eq. 5.7 in Ref. (1)):

q = A (r - r_0) + B (p - p_0) + c,

where q are the Perigee parameters wrt linPoint, {r_0} r is the {initial} 4D PCA position, {p_0} p is the {initial} momentum (phi, theta, q/p) at the PCA, and c is the constant term of the expansion. A and B are matrices of derivatives, denoted hereafter as "positionJacobian" and "momentumJacobian" respectively.

This class computes A and B using the analytic formulae of Ref. (1).

Ref. (1) - CERN-THESIS-2010-027, Giacinto Piacquadio (Freiburg U.)

Constructor & Destructor Documentation

HelicalTrackLinearizer()

Acts::HelicalTrackLinearizer::HelicalTrackLinearizer ( const Config & config, std::unique_ptr< const Logger > _logger = getDefaultLogger("HelTrkLinProp",                                                               Logging::INFO) )

explicit

Constructor.

Parameters

config	Configuration object
_logger	a logger instance

Member Function Documentation

linearizeTrack()

Result< LinearizedTrack > Acts::HelicalTrackLinearizer::linearizeTrack	(	const BoundTrackParameters &	params,
		double	linPointTime,
		const Surface &	perigeeSurface,
		const Acts::GeometryContext &	gctx,
		const Acts::MagneticFieldContext &	mctx,
		MagneticFieldProvider::Cache &	fieldCache ) const

Function that linearizes BoundTrackParameters at the PCA to a given Perigee surface.

Parameters

params	Parameters to linearize
linPointTime	Time associated to the linearization point

Note

Transverse plane of the Perigee corresponding to linPoint is parallel to the global x-y plane

Parameters

perigeeSurface	Perigee surface belonging to linPoint
gctx	Geometry context
mctx	Magnetic field context
fieldCache	Magnetic field cache

Returns

Linearized track