Observations of Cold Antihydrogen

Abstract

ATRAP's e+ cooling of p in a nested Penning trap has led to reports of cold H produced during such cooling by the ATHENA and ATRAP collaborations. ATHENA uses coincident annihilation detection and ATRAP uses field ionization followed by p storage. Advantages of the later method include the complete absence of a substantial background of false events intrinsic to the former, and the first way to measure which H states are produced. ATRAP enhances the H production rate by driving many cycles of e + cooling in the nested trap, with more H counted in an hour than the sum of all the other antimatter atoms ever reported. The number of H counted per incident high energy p is also higher than ever observed. The first measured distribution of H states is made using a pre-ionizing electric field between separated production and detection regions. The high rate and the high Rydberg states suggest that the H is formed via three-body recombination, as expected.