Pion-Helium Scattering above the (3,3) Resonance

Abstract

Differential cross sections are reported for ${\pi }^{+}$ + ${}_{}{}^{3,4}{}_{}{}^{}\mathrm{He}$ elastic scattering at 260, 295, and 310 MeV and ${\pi }^{-}$ + ${}_{}{}^{3,4}{}_{}{}^{}\mathrm{He}$ at 295 MeV. The angular distributions (except for ${\pi }^{-}$ + ${}_{}{}^3{}_{}{}^{}\mathrm{He}$) confirm the fixed angle ($\theta \approx 75°$) minimum seen at lower energies [caused by the (3,3) $\pi +N$ resonance dominance] and show a deep minimum at $\theta \approx 110°$. Comparisons are made to $\pi +d$ and the current discussion of pion excitation of intermediate dibaryon and $\Delta N$ states.