E. G. Judd

The STAR trigger

Abstract We describe the trigger system that we designed and implemented for the STAR detector at RHIC. This is a 10 MHz pipelined system based on fast detector output that controls the event selection for the much slower tracking detectors. Results from the first run are presented and new detectors for the 2001 run are discussed.

The STAR Vertex Position Detector

Abstract The 2×3 channel pseudo Vertex Position Detector (pVPD) in the STAR experiment at RHIC has been upgraded to a 2×19 channel detector in the same acceptance, called the Vertex Position Detector (VPD). This detector is fully integrated into the STAR trigger system and provides the primary input to the minimum-bias trigger in Au+Au collisions. The information from the detector is used both in the STAR Level-0 trigger and offline to measure the location of the primary collision vertex along the beam pipe and the event “start time” needed by other fast-timing detectors in STAR. The offline timing resolution of single detector channels in full-energy Au+Au collisions is ~100xa0ps, resulting in a start time resolution of a few tens of picoseconds and a resolution on the primary vertex location of ~1xa0cm.

Au+Au reactions at the AGS: Experiments E866 and E917

Particle production and correlation functions from Au+Au reactions have been measured as a function of both beam energy (2--10.7 AGeV) and impact parameter. These results are used to probe the dynamics of heavy-ion reactions, confront hadronic models over a wide range of conditions and to search for the onset of new phenomena.Particle production and correlation functions from Au+Au reactions have been measured as a function of both beam energy (2-10.7AGeV) and impact parameter. These results are used to probe the dynamics of heavy-ion reactions, confront hadronic models over a wide range of conditions and to search for the onset of new phenomena.

Particle production at the AGS: an excitation function

Abstract Experiments E866 and E917 at the AGS have measured the differential invariant yields of positive and negative charged kaons from Au+Au collisions at beam kinetic energies in the laboratory of 2, 4, 6, 8, and 10.8 A·GeV. At each beam energy, a multiplicity array is used to select on the centrality of the collision.

The centrality dependence of the source size for AuAu collisions at the AGS

Abstract Recent π − π − correlation measurements and deuteron to proton yield ratio measurements for Auue5f8Au collisions from Brookhaven E866 are presented. These measurements allow us, with some interpretation, to deduce the size of the participant region in a heavy ion collision. An unpredicted rise of the apparent source size is seen in the π − π − data at midrapidity. No corresponding drop in the deuteron to proton yield ratio is seen. Further experimental study is needed to improve the statistical significance of the correlation result and to determine whether it can be explained by conventional hadronic means.