The Aleph minivertex detector

The performance of the Aleph vertex detector is described. It consists of two layers of double- sided silicon strip detectors installed around the beam pipe of LEP, inside the Aleph apparatus. The purpose of the Vertex Detector is to measure with high accuracy both coordinates of the impact point of charged particles produced in Z0 decays. The physics goal is to identify events with beauty particles. The paper describes the different components of the detector: supporting structure, silicon detectors, electronics. Results on efficiency for m.i.p., space resolution and charge correlation for the two sides are shown. In particular, a space resolution of 13 μm in (r-φ) and 25 μm in (r-z) has been obtained with high momentum particles. The above values are in fairly good agreement with the expected performance for 100 and 200 μm pitch readout. Track matching efficiency, double track resolution and S/N measurement are presented. Cooling and radiation problems are discussed