Angular Distribution of Charge Exchange and Inelastic Neutrons inπ−−pInteractions at 313 and 371 MeV

Abstract

Neutron angular distributions from the charge-exchange (${\ensuremath{\pi}}^{0}n$) and inelastic modes (${\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}n,{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}n$) of the ${\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{-}p$ interaction have been investigated at 313 and 371 MeV incident-pion kinetic energy. The data were obtained with an electronic counter system. Elastic and inelastic neutrons were separated in the all-neutral final states by time of flight. At both energies the charge-exchange differential cross section at the forward neutron angles differs from that determined by Caris et al. from measurements of the ${\ensuremath{\pi}}^{0}$-decay gamma distributions, but generally agrees with the phase-shift-analysis calculations of Roper. The distribution of inelastic neutrons from both modes shows a strong preference for low center-of-mass neutron energies. The distribution of these neutrons does not correspond to that expected from the $I=0$, $\ensuremath{\pi}\ensuremath{-}\ensuremath{\pi}$ interaction (ABC effect) suggested to account for the anomaly in $p\ensuremath{-}d$ collisions observed by Abashian et al. Finally, all available charge-exchange differential-cross-section data from this and other experiments were combined by at least-squares fit to a Legendre expansion of the form $\frac{d\ensuremath{\sigma}}{d{\ensuremath{\Omega}}^{*}}({{cos\ensuremath{\theta}}_{{\ensuremath{\pi}}^{0}}}^{*})=\ensuremath{\Sigma}\stackrel{N}{l=0}{a}_{l}{P}_{l}({{cos\ensuremath{\theta}}_{{\ensuremath{\pi}}^{0}}}^{*})$ with the following results (in mb/sr):