6533b82cfe1ef96bd128fede

RESEARCH PRODUCT

Experience with the ALEPH silicon vertex detector

subject

description

Abstract The ALEPH experiment [1] at LEP is equipped with a vertex detector [2] using two layers of double-sided silicon strip detectors. These detectors allow a real two-dimensional measurement of charged particle tracks. The present (1991) detector has the inner layer at a radius of 6.5 cm and the outer layer at 11.5 cm. The theta angle coverage is ±33° for the inner layer and ±50° for the outer layer. The inner layer is made out of 9 faces with four silicon detectors each, the outer layer has 15 such faces. We use silicon detectors of 5 × 5 cm 2 and 300 μm thickness. The readout pitch is 100 μm at both sides and using capacitive charge division a resolution in the order of 10 μm can be achieved. The signals from 256 readout strips are integrated, amplified and multiplexed using four CAMEX64 chips. An early version of this detector was already installed in spring 1990. Although the detector was not complete and in addition was accidentally damaged by malfunctions of the external electronics, it took data during the 1990 ALEPH run. For the first time double sided silicon detectors were used in a physics experiment. In 1991 the beampipe was replaced by a smaller one. This allowed us to move the inner layer to a radius of 6.5 cm. A completely new detector has been built. This new detector has been installed in spring 1991. Most of the results quoted in this paper refer to this detector.