THE EXTENDED OPAL SILICON STRIP MICROVERTEX DETECTOR

The OPAL experiment at the CERN LEP collider recently increased the ge ometrical acceptance of its silicon microvertex detector. The azimutha l coverage is improved by adding one pair of detector modules to each of the two layers, while the polar angle coverage is extended by addin g new detector modules in line with the existing ones. This improves t he efficiency for high quality tracking in OPAL and in particular for b quark tagging in Higgs boson searches. A description of the detector is given, with emphasis on new or modified elements with respect to t he earlier version. Results on the performance of the new detector are presented. (C) 1998 Published by Elsevier Science B.V. All rights res erved.