We report the background-free observation of atomic antihydrogen, produced by interactions of an antiproton beam with a hydrogen gas jet target in the Fermilab Antiproton Accumulator. We measure the cross section of the reaction pp ! He 2 p for p beam momenta between 5203 and 6232 MeV͞c to be 1.12 6 0.14 6 0.09 pb. [S0031-9007(98)

A beam of relativistic antihydrogen atoms, the bound state (pe'), can be created by circulating the beam of an antiproton storage ring through an internal gas target. An antiproton that passes through the Coulomb field of a nucleus of charge Z will create e'e-pairs, and antihydrogen will form when a positron is created in a bound rather than a continuum state about the antiproton. The cross section for this process is calculated to be -4Z2 pb for antiproton momenta above 6 GeV/c. The gas target of Fermilab Accumulator experiment E760 has already produced -34 unobserved antihydrogen atoms, and a sample of -760 is expected in 1995 from the successive experiment E835. No other source of antihydrogen exists. A simple method for detecting relativistic antihydrogen is proposed and method outlined of measuring the antihydrogen Lamb shift to -1%.

A proof-of-principle electron electric-dipole-moment ͑e-EDM͒ experiment using slow cesium atoms, nulled magnetic fields, and electric-field quantization has been performed. With the ambient magnetic fields seen by the atoms reduced to less than 200 pT, an electric field of 6 MV/ m lifts the degeneracy between states of unequal ͉m F ͉ and, along with the low ͑Ϸ3 m/s͒ velocity, suppresses the systematic effect from the motional magnetic field. The low velocity and small residual magnetic field have made it possible to induce transitions between states and to perform state preparation, analysis, and detection in regions free of applied static magnetic and electric fields. This experiment demonstrates techniques that may be used to improve the e-EDM limit by two orders of magnitude, but it is not in itself a sensitive e-EDM search, mostly due to limitations of the laser system.