Session UB04 - Instrumentation for Nuclear Physics I.
ORAL session, Thursday morning, March 25
Room 204E, GWCC
The Broad Range Hadron Magnetic Spectrometers (BRAHMS) detector will be used to study collisions between ultra-relativistic heavy ions at RHIC. The BRAHMS Beam-Beam Counters (BBC) are arrays of Cerenkov radiators each attached to a photomultiplier tube. Phototube diameters are 19 mm or 51 mm, with 4cm long or 3cm long radiators, respectively. The BBC have the unique capability to detect particles at high positive and negative rapidities with good pulse height resolution, sufficient to determine charged particle multiplicities. The arrays are positioned on both sides of the interaction vertex. Coincidences between leading particles in the 2 arrays are used to provide a time zero for the other detectors in BRAHMS, to build a level-zero trigger, to be a component in determining the centrality of events, and for on-line vertex reconstruction. Results of test-beam studies and of GEANT simulations of the BBC's ability to measure primary and secondary particles will be presented.