First experience and results from the HERA-B vertex detector system

The HERA-B collaboration is building a detectorto realize the ambitious goal of observing CP violationin decays of neutral B-mesons. A central element of the apparatus is the silicon vertex detectorused to selectively trigger on these decays in a high charged particle multiplicity background environment and to reconstruct secondary vertices from such decays with high precision. The vertex detector, the supporting infrastructure and first results using prototype detectorsare described. Results include imaging of the proton interaction region on the HERA-B target, hit distributions in the detectorplanes, and alignment of the detectorswith each other and the target. ( 1998 Elsevier Science B.V. All rights reserved.