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

TL;DR

This paper reports the first observation and measurement of the branching fractions of $ ext{psi}(2S)$ decays to $p ar{n} ext{pi}^-$ and related channels, using a large dataset from BESII, and discusses resonance contributions.

Contribution

First observation of $ ext{psi}(2S)$ decays to $p ar{n} ext{pi}^-$ and detailed branching fraction measurements with background analysis.

Findings

Branching fractions for $ ext{psi}(2S) o p ar{n} ext{pi}^-$ and $ar{p} n ext{pi}^+$ determined.

Main background channels quantified and analyzed.

Resonance contributions in the decay process discussed.

Abstract

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