VxVertex

Author

Andre.nosp@m.as.W.nosp@m.ildau.nosp@m.er@c.nosp@m.ern.c.nosp@m.h

Kiril.nosp@m.l.Pr.nosp@m.okofi.nosp@m.ev@c.nosp@m.ern.c.nosp@m.h

Introduction

The VxVertex package provides the Event Data Model for reconstruction of primary and secondary vertexes. The extensions of VxVertex are also suitable to store the information about constrained vertices's, V0's, conversions etc. The top level object of the package is a Trk::VxContainer, which is returned e.g. by a primary vertex finder and represents a collection of Trk::VxCandidate. The latter one is the central object of the package, representing a reconstructed vertex candidate. It provides an information about a position of reconstructed vertex, covariance matrix and its track contents. In some case (e.g. constraint fitting) the full covariance matrix of the fit is also stored (see Trk::ExtendedVxCandidate).

Design

Trk::Vertex: A simplest vertex representation. Stores a 3d position only.

Trk::RecVertex: Inherits from the Trk::Vertex class. Stores a 3x3 covariance matrix and values related to the quality of the fit in addition.

Trk::VxCandidate: A reconstructed vertex candidate. Includes a Trk::RecVertex as a private data member. Also stores a collection of Trk::VxTrackAtVertex, thus providing information about tracks used in the fit and their initial and refitted states.

Trk::VxTrackAtVertex: Represents the tracks used in the vertex fit. Contains links to initial track parameters, reconstructed track (if any), refitted state of the track (if any). Also provides various measures of track compatibility to the fitted vertex, such as Chi2, weight etc. The actual use depends strongly on the concrete fitter.

Trk::ExtendedVxCandidate: Extends the Trk::VxCandidate with a full covariance matrix of the fit. The latter one is supposed to include all track-track, track-vertex and vertex-vertex inter component correlations.

Trk::LinearizedTrack: A class providing parameters of the first order Taylor expansion of the measurement equation. This is a storage place for various parameters required during the iterative vertex fit.

VxContainer: A top level object of this package. This is a container of vertexes to be written to the StoreGate as a result of a vertex reconstruction.