Using $(1.0087\pm 0.0044)\times {10}^{10}J/\psi$ events collected with the BESIII detector at the BEPCII storage ring, the process ${\mathrm{\Xi }}^{0}n\to {\mathrm{\Xi }}^{-}p$ is studied, where the ${\mathrm{\Xi }}^0$ baryon is produced in the process $J/\psi \to {\mathrm{\Xi }}^0{\overline{\mathrm{\Xi }}}^0$ and the neutron is a component of the ${}^9\mathrm{Be}$, ${}^{12}\mathrm{C}$, and ${}^{197}\mathrm{Au}$ nuclei in the beam pipe. A clear signal is observed with a statistical significance of $7.1\sigma$. The cross section of the reaction ${\mathrm{\Xi }}^0+{}^9\mathrm{Be}\to {\mathrm{\Xi }}^{-}+p+{}^8\mathrm{Be}$ is determined to be $\sigma ({\mathrm{\Xi }}^0+{}^9\mathrm{Be}\to {\mathrm{\Xi }}^{-}+p+{}^8\mathrm{Be})=(22.1\pm {5.3}_{\mathrm{stat}}\pm {4.5}_{\mathrm{sys}})\mathrm{mb}$ at the ${\mathrm{\Xi }}^0$ momentum of $0.818\mathrm{GeV}/c$, where the first uncertainty is statistical and the second is systematic. No significant $H$-dibaryon signal is observed in the ${\mathrm{\Xi }}^{-}p$ final state. This is the first study of hyperon-nucleon interactions in electron-positron collisions and opens up a new direction for such research.

• Received 27 April 2023
• Revised 20 May 2023
• Accepted 25 May 2023

DOI:https://doi.org/10.1103/PhysRevLett.130.251902

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Published by the American Physical Society