First observation of $ψ(2S) \to p \bar{n} π^- +c.c.$

Abstract

Using 14 million $ψ(2S)$ events collected with the Beijing Spectrometer (BESII) at the Beijing Electron-Positron Collider, the branching fractions of $ψ(2S)$ decays to $p \bar{n} π^-$ and $\bar{p} n π^+$ and the branching fractions of the main background channels $ψ(2S) \to p \bar{n} π^-π^0$, $ψ(2S) \to γχ_{c0} \to γp \bar{n} π^-$, $ψ(2S) \to γχ_{c2} \to γp \bar{n} π^-$, and $ψ(2S) \to γχ_{cJ} \to γp \bar{n} π^- π^0$ are determined. The contributions of the $N^{\ast}$ resonances in $ψ(2S) \to p \bar{n} π^- +c.c.$ are also discussed.