We have identified the annihilation mode $\overline{p}p\to 2{\pi }^0$ for antiprotons stopping in liquid hydrogen at a rate which is 0.15 (±20%) times that reported for $\overline{p}p\to {\pi }^{+}{\pi }^{-}$. This indicates that about 40% of all annihilations into $2\pi$ take place from odd-orbital atomic $\overline{p}p$ states, in contrast to the usual assumption that annihilation from the $s$ state predominates.

• Received 18 October 1971

DOI:https://doi.org/10.1103/PhysRevLett.27.1614