Antiprotons and the Crystal Ball

Abstract

During the 1998 running of the Crystal Ball experiment, a couple of brief test runs were done with the C6 beamline tuned to produce antiprotons. Specifically, one shift on July 29th produced runs 329-334 with the beam momentum set for 650 MeV/c, run 355 was done on July 31st with a 550 MeV/c beam momentum, and run 926-929 were obtained in a single shift on November 3rd, also with a beam momentum of 550 MeV/c. The beam tune for the November data was greatly superior to that of the July data, however. Therefore, only the November data have been analyzed in detail, and the results of this analysis are presented in this note. Due to the paucity of statistics that were obtained, it was decided not to attempt to publish the results. However, the results are valuable as a tool for planning a possible future program of dedicated measurements of antiproton-proton annihilation into all-neutral final states using the Crystal Ball. The data in fact show that the Crystal Ball with its large angular acceptance and multi-photon capability would be an excellent detector for such an experiment. Only one other such experiment (the Crystal Barrel experiment at CERN/LEAR) has ever been done in the past. Also in this document is a survey of published results for old antiproton-proton experiments, some discussion of physics issues that are relevant to measurements of {anti p} + p {r_arrow} all-neutral final states, and some estimates about the kinds of experiments they could contemplate doing in the C6 and D6 lines at the AGS.