Ratio of antiproton annihilations on neutrons and protons in carbon for low-energy and stopped antiprotons

Abstract

The ratio $\frac{N(\overline{p}n)}{N(\overline{p}p)}$ is measured for stopping $\overline{p}$ in propane and is found to be 0.63\ifmmode\pm\else\textpm\fi{}0.06, in good agreement with Bugg et al. Comparison of this number with the same ratio obtained in deuterium (0.763\ifmmode\pm\else\textpm\fi{}0.019) suggests resonant structure of the $\overline{p}N$ system near threshold. $\frac{N(\overline{p}n)}{N(\overline{p}p)}$ is measured for inflight carbon annihilations; the results are consistent with a $\overline{p}N$ resonance near 1932 MeV seen earlier by Carroll et al. and also identify the resonance as being an $I=1$ state.