B. Libby

Search for exotic strange quark matter in high energy nuclear reactions

Abstract We report on a search for metastable positively and negatively charged states of strange quark matter in Au+Pb reactions at 11.6 A GeV/ c in experiment E864. We have sampled approximately six billion 10% most central Au+Pb interactions and have observed no strangelet states (baryon number A −8 per central collision. These limits are the best and most model independent for this colliding system. We discuss the implications of our results on strangelet production mechanisms, and also on the stability question of strange quark matter.We report on a search for metastable positively and negatively charged states of strange quark matter in Au+Pb reactions at 11.6 A GeV/c in experiment E864. We have sampled approximately six billion 10% most central Au+Pb interactions and have observed no strangelet states (baryon number A<100 droplets of strange quark matter). We thus set upper limits on the production of these exotic states at the level of 1-6 x 10^{-8} per central collision. These limits are the best and most model independent for this colliding system. We discuss the implications of our results on strangelet production mechanisms, and also on the stability question of strange quark matter.

A study of MWPC with chevron cathode pad readout

Abstract An investigation of MWPCs with interpolating chevron shaped cathode pad readout has been carried out as part of the R&D for the particle tracking system of the PHENIX detector at RHIC. Two prototype chambers were designed and constructed. Their response to minimum ionizing particles was tested with secondary beams from the AGS accelerator system at the Brookhaven National Laboratory. Results on resolution, differential non-linearity and overall performance for different chevron patterns and cell geometries are presented.

Particle identification in TEC/TRD Prototypes for the PHENIX detector at RHIC

The tracking system in the PHENIX detector at RHIC has been designed to track charged particles in a high track density environment (dNcdy = 1500). This corresponds to ∼500 charged particles, primarily pions, in the fiducial volume of the detector, with a spectrum peaked at ∼250 MeV/c. The TEC/TRD subsystem will track all charged particles and contribute to the particle identification between 200 MeV/c and 2.5 MeV/c by performing fine sampling energy loss (dEdx) measurements. Prototype chambers were tested in a secondary beam of negatively charged particles at the AGS. An electron-pion separation at levels up to a factor of 200 by dEdx was measured. This separation factor was measured as a function of the particle momentum and angle, and the gain and gas mixture used in the chamber.

A high mass trigger for the E864 experiment at the AGS accelerator

Abstract The E864 experiment at the AGS is designed to carry out high sensitivity searches for a variety of possible new particles using relativistic heavy ion Au beams on Pb and Pt targets. In order to reach the desired sensitivities, a level-2 “late energy” trigger was built to select events in which a heavy particle is detected in a hadronic calorimeter with deposited energy and time-of-flight from the target exceeding preset values. The physics motivation for the trigger is discussed and and details of its hardware and software design are given. Performance results from recent E864 data taking runs are presented.

A spectrometer for study of high mass objects created in relativistic heavy ion reactions

Abstract Experiment E864 at the Brookhaven AGS accelerator uses a high sensitivity, large acceptance spectrometer, designed to search for strangelets and other novel forms of matter produced in high-energy heavy ion collisions. The spectrometer has excellent acceptance and rate capabilities for measuring the production properties of known particles and nuclei such as p, d and 6 He . The experiment uses a magnetic spectrometer and employs redundant time of flight and position detectors and a hadronic calorimeter. In this paper we describe the design and performance of the spectrometer.

Electromagnetic dissociation of Au targets by Au beams in E862

E862 is an experiment to measure Electromagnetic Dissociation (ED) of Au and Co targets by 9.89 GeV/nucleon beams from the AGS. ED occurs at impact parameters large enough so that no strong interaction occurs, but virtual photons are exchanged, resulting in the excitation of a giant resonance. The authors report the first observation of an ED cross section {sigma}{sub ED} larger than the total hadronic cross section for Au+Au of 6.1 barns. Results are given for both the single- and double-neutron removal processes and compared to calculations using both semiclassical and quantum methods, including effects from both E1 and E2 giant resonances. Predictions are extended to RHIC and LHC collider energies where ED will be a significant determinant of the quality of the stored beams.