THE OPAL SILICON STRIP MICROVERTEX DETECTOR WITH 2 COORDINATE READOUT

The OPAL experiment at the CERN LEP collider recently upgraded its sil icon strip microvertex detector from one coordinate readout (phi only) to two coordinate readout (phi and z). This allows three dimensional vertex reconstruction and should improve lifetime measurements as well as b quark jet identification. This paper describes the new microvert ex detector system with emphasis on the novel techniques and new compo nents used to obtain the second coordinate information. These include the use of back-to-back single-sided detectors with orthogonally orien ted readout strips, a gold printed circuit on a thin glass substrate t o route the z strip signals to the electronics at the end of the detec tor, and the use of MX7 readout chips. Results on the performance of t he new detector are presented.