Peripheral Production in the Single-Meson-Exchange Forbidden Reactionπ−p→Y*−K+at 2 to 4 GeV/c

Abstract

Data are presented showing that the $Y_1^{}{}_{}{}^{*}\mathrm{}\left(1385\right)\mathrm{}$ production angular distribution in the reaction ${\pi }^{-}p\to Y^{*-}{K}^{+}$ and in its charge-symmetric counterpart ${\pi }^{+}n\left(p_{\mathrm{sp}}\right)\to Y^{*+}{K}^0\left(p_{\mathrm{sp}}\right)$ is characterized by peripheral ($\hat{N}·{\hat{Y}}^{*}\approx +1\mathrm{}$) and antiperipheral peaking. Explanation for the latter is sought in terms of baryon exchange; so comparisons with other $\pi N\to Y^{*}K$ reactions are made. The peripheral peak cannot arise through the exchange of any known meson. Alternative explanations are considered.