First study of reaction Ξ⁰n→Ξ⁻p using Ξ⁰-nucleus scattering at an electron-positron collider

Using (1.0087±0.0044)×10¹⁰ $J/ψ$ events collected with the BESIII detector at the BEPCII storage ring, the process Ξ⁰n→Ξ⁻p is studied, where the Ξ⁰ baryon is produced in the process J/ψ→Ξ⁰Ξ⁰ and the neutron is a component of the ⁹Be, ¹²C and ¹⁹⁷Au nuclei in the beam pipe. A clear signal is observed with a statistical significance of $7.1σ$. The cross section of the reaction Ξ⁰+⁹Be→Ξ⁻+p+⁸Be is determined to be σ(Ξ⁰+⁹Be→Ξ⁻+p+⁸Be)=(22.1±5.3ₛₜₐₜ±4.5sys) mb at the Ξ⁰ momentum of $0.818$ GeV/c, where the first uncertainty is statistical and the second is systematic. No significant H-dibaryon signal is observed in the Ξ⁻p final state. This is the first study of hyperon-nucleon interactions in electron-positron collisions and opens up a new direction for such research.