R. Bossingham

Measurement of electron capture from e+‐e− pair production by 0.956 GeV/u U92+ on Au, Ag, Cu, and Mylar targets

We describe the first experimental observation of electron capture from electron‐positron pair production in relativistic heavy ion collisions. We have used a novel new spectrometer to make the measurement of the cross section for a 0.956 GeV/u U92+ beam produced at the BEVALAC facility at LBL on Au, Ag, Cu, and Mylar targets. We also measured the energy and angular distribution of the positrons for the Au target. The total cross section for a Au target is measured to be 2.19 (0.25) barns for capture from pair production and 3.30 (0.65) barns for pair production without capture.

Identified particle elliptic flow in √sNN = 130 GeV

We report first results on elliptic flow of identified particles at mid-rapidity in Au+Au collisions at

Capture from pair production as a beam loss mechanism for heavy ions at RHIC

sqrt{s_{_{NN}}}=130

Measurement of electron capture from electron-positron pair production in relativistic heavy ion collisions.

GeV using the STAR TPC at RHIC. The elliptic flow as a function of transverse momentum and centrality differs significantly for particles of different masses. This dependence can be accounted for in hydrodynamic models, indicating that the system created shows a behavior consistent with collective hydrodynamical flow. The fit to the data with a simple model gives information on the temperature and flow velocities at freeze-out.

CAPTURE, IONIZATION, AND PAIR-PRODUCTION PROCESSES IN RELATIVISTIC HEAVY-ION COLLISIONS IN THE 1-GEV/NUCLEON ENERGY RANGE

Electron capture from electron-positron pair production is predicted to be a major source of beam loss for the heaviest ions at RHIC. Achieving the highest luminosity thus requires an understanding of the capture process. We report measurements of this process at Brookhaven National Laboratorys AGS using 10.8 GeV/nucleon Au/sup 79+/ projectiles on Au targets. Capture from pair production is a process in which the very high electromagnetic field involved in the collision of two relativistic heavy ions results in the production of an electron-positron pair with the capture of the electron by one of the ions. There are many theoretical papers published on capture from pair production with discrepancies between predicted cross sections. The experimental results are compared to theory and to previous experiments at 1 GeV/nucleon. The implications of extrapolations to RHIC energies are presented.