First Production of Cold Antihydrogen Atoms

Michael H. Holzscheiter, P-23

A theoretical underpinning of the Standard Model of fundamental particles and interactions is CPT invariance, which requires that the laws of physics be invariant under the combined discrete operations of charge conjugation, parity, and time reversal. Antimatter, the existence of which was predicted by Dirac, can be used to test the CPT theorem. Comparing the properties of hydrogen and antihydrogen would allow a new precise test, as CPT invariance implies that they must have the same spectrum.

Observations of antihydrogen in small quantities and at high energies have been reported at the European Organization for Nuclear Research (CERN) and at Fermilab, but these experiments were not suited to precision comparison measurements. Here, I report on the just-announced copious production of antihydrogen atoms by our collaboration at CERN at very low energy by mixing trapped antiprotons and positrons in a cryogenic environment. The neutral antiatoms have been detected directly when they escape the trap and annihilate, producing a characteristic signature in an imaging particle detector.

It is noteworthy that many of the original ideas for this work were developed here at Los Alamos and that many of my colleagues have contributed along this rocky road to success. But somewhere during the trip Los Alamos was derailed off the tracks. However, we still have time to recover because this is only one step, albeit a great step, along the exciting experimental path Los Alamos initiated, which hopefully will culminate in our original goal, the measurement of gravity on antimatter.

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