PRODUCTION OF RELATIVISTIC ANTIHYDROGEN ATOMS BY PAIR PRODUCTION WITHPOSITRON CAPTURE AND MEASUREMENT OF THE LAMB SHIFT

A beam of relativistic antihydrogen atoms - the bound state (pe+BAR) - can be created by circulating the beam of an antiproton storage ring through an internal gas target. An antiproton which passes through the Coulomb field of a nucleus will create e+e- pairs, and antihydrogen w ill form when a positron is created in a bound instead of continuum st ate about the antiproton. The cross section for this process is roughl y 3 Z2 pb for antiproton momenta about 6 GeV/c. A sample of 600 antihy drogen atoms in a low-emittance, neutral beam will be made in 1995 as an accidental byproduct of Fermilab experiment E760. We describe a sim ple experiment, Fermilab Proposal P862, which can detect this beam, an d outline how a sample of a few-10(4) atoms can be used to measure the antihydrogen Lamb shift to 1 %.