Observation of the Reactionπ−p→pp¯nat 8GeVc

We have observed the reaction ${\pi }^{-}p\to p\overline{p}n$ at 8 $\frac{\mathrm{GeV}}{c}$ with a cross section of 97±26 μb. Because this reaction does not possess a distinctive topology in the bubble chamber which could distinguish it from the more frequent two-prong final states involving a nucleon and some number of pions, we have performed tests independent of the kinematic fitting process to confirm the presence of this reaction. These tests made use of the $\delta$ rays and secondary interactions produced by the negative tracks of our events. We have also investigated the possibility of various forms of contamination. Our final sample of events contains about 60% $p\overline{p}n$ final states and 40% background.