Reactionπ−p→γγnat 3.65GeVc

Abstract

New results are presented for the reactions ${\pi }^{-}p\to m^{0}n$ at 3.65 $\frac{\mathrm{GeV}}{c}$, where $m^0$ represents $\eta$ or ${\eta }^{\prime }$ decaying to $\gamma \gamma$. We have seen 31 ${\eta }^{\prime }$ events over a small background, leading to a branching ratio $\frac{({\eta }^{\prime }\to \gamma \gamma )}{({\eta }^{\prime }\to \mathrm{all})}={0.020}_{-0.006\mathrm{}}^{+0.008\mathrm{}}$. Over 2000 $\eta$ events were observed, and the differential cross section exhibits a dip at —$t=1.5\mathrm{}{\left(\frac{\mathrm{GeV}}{c}\right)}^2$.