Array of scintillator counters for PHOBOS at RHIC

An array of scintillator counters ("paddle counters") for the measurement o f number and energy of charged particles in heavy-ion gold-gold collisions for the PHOBOS experiment at RHIC is described. These simple, versatile, an d highly efficient detectors provide a low bias and an easily understood le vel zero trigger. The paddle counters can also be used to select and measur e event centrality. The information from the paddle counters used for trigg ering and event selection included the total signal height (proportional to the number of particles), the timing information of the hits, and the numb er of scintillators fired. The general characteristics of the paddle counte rs, their design parameters, and performance during the first run at RHIC a re presented in this paper, (C) 2001 Elsevier Science B.V. All rights reser ved.