The STAR Level-3 Trigger System - Year 0 Experiences

Jens Soeren Lange

Frankfurt University

The level-3 trigger system at the STAR experiment performs full online event reconstruction for Au+Au and p+p collisions at RHIC, using processor farms of 432 Intel i960 processors for xyz hit determination and 12 (later 48) ALPHA processors for track finding. Moreover, the system provides a hardware-accelerated event display, which has been used about 1.5 million STAR events in 3 months data taking. As a preliminary benchmark, high multiplicity central Au+Au events (130.000 hits, 6000 tracks) could be reconstructed in t<160 ms (including online dE/dx).

For the next years, several trigger on rare events are proposed, such as heavy fragments (e.g. anti-alpha), high-pT hadrons (hard scattering) or lepton pair production (J/Psi->e+e- and Upsilon->e+e-).