Observation of Atomic Antihydrogen

Abstract

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 $\overline{p}p\ensuremath{\rightarrow}\overline{H}{e}^{\ensuremath{-}}p$ for $\overline{p}$ beam momenta between 5203 and 6232 MeV/ $c$ to be $1.12\ifmmode\pm\else\textpm\fi{}0.14\ifmmode\pm\else\textpm\fi{}0.09$ pb.