COMMISSIONING OF THE DELPHI PIXEL DETECTOR

The DELPHI Vertex Detector has been upgraded for LEP200 with 2 layers of pixel detectors and 2 layers of ministrips as endcaps, thus coverin g the polar angular range between 10 degrees and 21 degrees and allowi ng for standalone pattern recognition. During the 1995/96 shutdown the first 95 modules were installed and the installation was completed in May 97 with all 152 modules. Production yields and failures during th e assembly will be presented. The detector operated at a threshold of around 9000 electrons resulting in a number of noisy pixels at the 10( -3) level. After masking these hot pixels in the readout, the remainin g number of random hits per event is at the 10(-6) level. The observed resolution of about 100 mu m is close to the expectation for binary r eadout. The track reconstruction efficiency increased by more than 100 % in the central part of the forward tracker. (C) 1998 Elsevier Scienc e B.V. All rights reserved.