Search

Interactions of 1.61-Bev/c antiprotons in hydrogen yielding two charged particles have been studied, with particular attention to elastic scattering, single-pion production, and annihilation into three or more pions. Effects of misinterpretation of events are estimated by Monte Carlo calculations. Nine partial cross sections have been measured. The elastic-scattering data show a secondary diffraction peak at about 82 deg in the center-of-mass system. Single pion production is found to be consistent with charge-conjugation invariance. In the single pion events (p + p yields N + N + pi ) the predominance of low- momentum transfer exceeds that predicted by the single pion exchange formula of Chew and Low. No two-pion resonances have been observed anywhere in the data. (auth)

Deviations from the expected two-pion effective-mass distributions have been found in the reaction $\overline{p}+p\ensuremath{\rightarrow}2{\ensuremath{\pi}}^{+}+2{\ensuremath{\pi}}^{\ensuremath{-}}+n{\ensuremath{\pi}}^{0}$. These occur in two regions, 300 Mev and 750 Mev, and could be explained by the $T=0$, pion-pion interaction reported by Abashian, Booth, and Crowe and the widely observed $\ensuremath{\rho}$ meson ($T=1$, $J={1}^{\ensuremath{-}}$ pion-pion resonance). The data in the 750-Mev region for ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ combinations ($Q=0$) show an apparent double-peak structure---one at 720 Mev ($\ensuremath{\Gamma}=20$ Mev), the other at 780 Mev ($\ensuremath{\Gamma}=60$ Mev). However, the $|Q|=1$ data (${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ combinations) are consistent with the previously observed single $T=1$, $J={1}^{\ensuremath{-}}$ resonance. Our data give ${M}_{\ensuremath{\rho}}=767$ Mev ($\ensuremath{\Gamma}=110$ Mev). As these parameters also fit the $Q=0$ data, a detailed discussion of the statistical significance of the one-peak and two-peak hypotheses is given. A search has been made for possible neutral modes of decay of the heavy mesons, and no evidence has been found.

Proton-antiproton annihilations at 1.61 13ev/c with only two mesons in the final state have been examined in the 72-in. bubble chamber. The partial cross sections measured are: p + p yields pi /sup -/ + pi /sup +/, 119 plus or minus 30 mu b; p + p yields K/sup -/ + K/sup +/, 55 plus or minus 18 mu b. The K/sup -/ distribution in p + p yields K/sup -/ + K/sup +/ is peaked strongly forward, with 7 of the 11 k/sup -/ mesons produced in the forwardmost tenth of the total solid angle. The pi /sup -/ events show no such effect, with only 2 of the 22 pi /sup -/ mesons being produced in the same forward interval. Careful study of possible contamination of these events indicates that almost all of them are genuine two-meson annihilations. (auth)