Improvement of the Kalman Filter Fit of the ZEUS experiment

Abstract

At the center of the ZEUS detector situated on the collider HERA at DESY in Hamburg, a Micro Vertex Detector has been installed in 2000/01. Situated close to the beam line, this subdetector is designed to measure precisely the tracks near the interaction point (the vertex). A package called KFFIT is designated to perform the track fit of the Micro Vertex Detector hits using a Kalman Filter. This paper is a report of all improvements done in this package. After a brief description of the algorithm, the improvements of KFFIT will be presented comparing the last version (v10 released in December 2006) to the initial one (v1 released in December 2005 (=v2005a.1)).