The ARGUS Vertex Trigger

Abstract

A fast second level trigger has been developed for the ARGUS experiment which recognizes tracks originating from the interaction region. The processor compares the hits in the ARGUS Micro Vertex Drift Chamber to 245760 masks stored in random access memories. The masks which are fully defined in three dimensions are able to reject tracks originating in the wall of the narrow beampipe of 10.5 mm radius. 1 Introduction In 1991 a new vertex detector was installed into the ARGUS experiment [1] which should allow tagging of heavy flavour decays by a precision reconstruction of secondary vertices. The system consists of a high resolution drift chamber [2] and a silicon strip detector [3]. Together with the installation of these components the radius of the beam pipe around the interaction region was decreased to only 10.5 mm, in order to keep the lever arm of the reconstructed tracks to the vertex as short as possible. Aperture limiting elements within the beampipe move even as close as 9 mm..