Charge-Exchange Production of Antineutrons and their Annihilation in Hydrogen

Abstract

The charge exchange of antiprotons into antineutrons and the subsequent annihilation of antineutrons have been studied in the 72-in. liquid-hydrogen bubble chamber. The antiprotons were produced internally in the Bevatron; channeled externally by collimation, quadrupole focusing magnets, and bending magnets; and separated from other negatively charged particles by a system of three velocity spectrometers. Analysis of the data for a run with an antiproton momentum of 1.61 Bev/c has been completed. Three charge-exchange reactions have been studied: (a) $\overline{p}+p\to \overline{n}+n$, (b) $\overline{p}+p\to \overline{n}+n+{\pi }^0$, and (c) $\overline{p}+p\to \overline{n}+p+{\pi }^{-}$. The cross section for Reaction (a) plus Reaction (b) was found to be strongly peaked forward with a value for the angular differential cross section at zero degrees of 4.6±0.5 mb/sr. The total cross section for these two reactions was found to be 7.82±0.55 mb. The total cross section for Reaction (c) was found to be 0.99±0.24 mb; the statistical model would predict the cross section for (b) to be about the same as (c).