This wiki page is intended to describe a primary vertex finder based on VKalVrt vertex reconstruction package.


VKalVrtPrim reconstructs primary vertex (+pileup vertices if present) based on xKalman or iPatRec reconstructed tracks. For the moment the output is written into the SimpleVertex class (other output classes will be available soon). After work of the VKalVrtPrim algorithm a SimpleVertexContainer with name VKalPVrtContainer is present in TES.

VKalVrtPrim makes primary vertex reconstruction both for low and high luminosity pileup. For events with pileup it's assumed in VKalVrt that the first reconstructed vertex in the container is the primary one. The remaining vertices are pileup.

Vertices reconstructed by VKalVrtPrim are used in b-tagging.

CBNT variables

NVrtP Total number of reconstructed beam vertices
PVrtX X of vertex
PVrtY Y of vertex
PVrtZ Z of vertex
PVrtCxx vertex covariance matrix
PVrtCxy vertex covariance matrix
PVrtCyy vertex covariance matrix
PVrtCxz vertex covariance matrix
PVrtCyz vertex covariance matrix
PVrtCzz vertex covariance matrix
PVrtCh2 Chi2 of vertex
PVrtNdf Number of degree of freedom
PVrtId Vertex identification ( ==1 for the moment)
PVrtSel Vertex selection variable (see below for details)


A C++ version of the same algorithm is available. It works both on AOD and ESD ( any of Trk::Track or Rec::TrackParticle containers may be used as input) and gives a full control on vertex finding procedure through jobOptions (see VKalVrtAthena.py and comments inside for details)

High luminosity cleaning

-- VadimKostyukhin - 24 Nov 2005

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Topic revision: r4 - 2006-03-26 - VadimKostyukhin
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