Cross Section Measurements of $\bar{n}p \rightarrow K^{+}K^{-}\pi^{+}(\pi^{0})$ via Antineutrons Produced by $J/\psi \to p \pi^{-} \bar{n}$ Decays

TL;DR

This study measures antineutron-proton inelastic scattering cross sections using a novel method with $J/ar{n}$ decays at BESIII, providing new data on these interactions over a broad momentum range.

Contribution

Introduces a new approach to produce and tag antineutrons via $J/ar{n}$ decays, enabling cross section measurements of $ar{n}p$ reactions with high statistics.

Findings

Measured flux-averaged cross sections for $ar{n}p ightarrow K^{+}K^{-} ho^{+}$ and $ar{n}p ightarrow K^{+}K^{-} ho^{+} ho^{0}$.

Antineutron-proton scattering candidates observed, demonstrating the method's potential for future studies.

Cross sections are consistent with previous measurements within uncertainties.

Abstract

Based on a novel method for producing antineutrons via $J/\psi$ decays, we report a study of $\bar{n}p$ inelastic scattering into final states containing kaons. The analysis uses $(10087\pm44)\times 10^6$ $J/\psi$ events collected at the BESIII detector operating at the BEPCII storage ring. Antineutrons are produced via $J/\psi \to p \pi^{-} \bar{n}$ decays and tagged by the detected protons and pions, resulting in antineutron momenta ranging from 0 to 1174~MeV/$c$, while target protons are provided by the hydrogen in the beam-pipe material. The flux-averaged cross sections of the reactions $\bar{n}p \rightarrow K^{+}K^{-}\pi^{+}$ and $\bar{n}p \rightarrow K^{+}K^{-}\pi^{+}\pi^{0}$ over this antineutron momentum spectrum are measured to be $0.53^{+0.15}_{-0.12} \pm 0.08$~mb and $1.09^{+0.36}_{-0.30} \pm 0.31$~mb, respectively, where the first uncertainties are statistical and the second are systematic. Due to limited statistics, the intermediate states in these processes are not quantitatively investigated. The observation of clean antineutron-proton scattering candidates indicates the potential of this approach for future investigations of antineutron-proton interactions.