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

Neutron angular distributions from the charge-exchange (${\pi }^{0}n$) and inelastic modes (${\pi }^0{\pi }^{0}n,{\pi }^{+}{\pi }^{-}n$) of the ${\pi }^{-}-p$ 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 ${\pi }^0$-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 $I=0\mathrm{}$, $\pi -\pi$ interaction (ABC effect) suggested to account for the anomaly in $p-d$ 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 $\frac{d\sigma }{d{\Omega }^{*}}\left({{cos\theta }_{{\pi }^0}}^{*}\right)=\Sigma \stackrel{N}{l=0\mathrm{}}{a}_l{P}_l\left({{cos\theta }_{{\pi }^0}}^{*}\right)$ with the following results (in mb/sr):