Analyzing powers and partial wave decomposition of p n --> p p((1)S(0)) pi- at low-energies

Analyzing powers for $\stackrel{\ensuremath{\rightarrow}}{p}n\ensuremath{\rightarrow}\mathrm{pp}(^{1}S_{0}){\ensuremath{\pi}}^{\ensuremath{-}}$ were measured at beam energies 353, 404, and 440 MeV by extracting the quasifree process from $\stackrel{\ensuremath{\rightarrow}}{p}d\ensuremath{\rightarrow}\mathrm{ppp}{\ensuremath{\pi}}^{\ensuremath{-}}$. Partial wave amplitude analysis yields a significant contribution from the isospin 1, $s$-wave channel. This contribution is relatively much larger than that expected from theoretical models which have been successful in describing the isospin 1, $s$-wave channel behavior of $\mathrm{pp}\ensuremath{\rightarrow}\mathrm{pp}{\ensuremath{\pi}}^{0}$ cross sections at threshold.