Peripheral p$\overline{p}$ production and decay angular distribution in the reaction $\pi^{-}p\rightarrow\p\overline{p}$n at 18.8 and 9.8 GeV

A total of 13920 pi /sup -/p to ppn events measured in a spark chamber experiment at 9.8 GeV incident pi /sup -/ momentum are compared with data recently published on the same reaction at 18.8 GeV. The s- dependence of the total cross section, the shape of d/sup 2/ sigma /d Mdt, and the pp decay angular distributions at both energies suggest that the production process is dominated by one-pion exchange. This is supported by comparison with new pi /sup +/p to pnp and pp to pi /sup +/ pi /sup -/ annihilation data. An interpretation of the angular distribution by partial waves is discussed, and results from a fit with a Breit-Wigner parametrization are presented. The cross section for the reaction pi /sup -/p to ppn in the range M/sub pp/<or=2.7 GeV and mod t/sub np/ mod <or=0.3 GeV/sup 2/ has been determined to be sigma =6.5+or-0.9 mu b at 9.8 GeV. (23 refs).