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

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 the first observation and measurement of this process, in Bevalac experiments using 1 GeV/u U⁹²⁺ 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 polarizes the vacuum, resulting in the production of an electron-positron pair and the capture of the electron by one of the ions. There are many theoretical papers published on capture from pair production with very large discrepancies between predicted cross sections. The experimental results are compared to theory, and the implications of extrapolations to RHIC energies are presented