Study of the reactions $\bar{n} p \to 2\pi^{+}\pi^{-}$, $2\pi^{+}\pi^{-}\pi^{0}$, and $2\pi^{+}\pi^{-}2\pi^{0}$ using $J/\psi \to p \pi^{-}\bar{n}$

TL;DR

This paper presents the first experimental data on antineutron-proton reactions at high momenta, using a novel method at an $e^{+}e^{-}$ collider with a large dataset from BESIII.

Contribution

It introduces a new experimental approach to study $ar{n}$-nucleon interactions at momenta above 800 MeV/$c$ using $J/3$ decays.

Findings

Collected over 10 billion $J/3$ events at BESIII.

Reactions studied include $ar{n} p o 2\u03c0^{+}c extc^{-}$, $2\u03c0^{+}c extc^{-}}c^{0}$, and $2\u03c0^{+}c extc^{-}2\u03c0^{0}$.

Pioneered the study of $ar{n}$-nucleon interactions at an $e^{+}e^{-}$ collider.

Abstract

We report an experimental investigation of the reactions $\bar{n} p \to 2\pi^{+}\pi^{-}$, $\bar{n} p \to 2\pi^{+}\pi^{-}\pi^{0}$, and $\bar{n} p \to 2\pi^{+}\pi^{-}2\pi^{0}$ using $(10.087 \pm 0.044) \times 10^{9}$ $J/\psi$ events collected with the BESIII detector at the BEPCII storage ring. The antineutron ($\bar{n}$) is produced in the decay $J/\psi \to p \pi^{-} \bar{n}$ with studied momentum from 200~MeV/$c$ to 1174~MeV/$c$, while the target proton originates from the hydrogen nuclei in the cooling oil of the beam pipe. This novel method pioneers the study of $\bar{n}$-nucleon interactions at an $e^{+}e^{-}$ collider, providing the first experimental data for $\bar{n}$ momenta exceeding 800~MeV/$c$.