First study of reaction ${\Xi }^{0}n\to {\Xi }^{-}p$ using ${\Xi }^0$-nucleus scattering at an electron-positron collider

Abstract

Using $(1.0087\pm 0.0044)\times 10^{10}$ $J/\psi$ events collected with the BESIII detector at the BEPCII storage ring, the process ${\Xi }^{0}n\to {\Xi }^{-}p$ is studied, where the ${\Xi }^0$ baryon is produced in the process $J/\psi \to {\Xi }^0{\bar{\Xi }}^0$ 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 ${\Xi }^0+{}^9\mathrm{Be}\to {\Xi }^{-}+p+{}^8\mathrm{Be}$ is determined to be $\sigma ({\Xi }^0+{}^9\mathrm{Be}\to {\Xi }^{-}+p+{}^8\mathrm{Be})=(22.1\pm 5.3_{\mathrm{stat}}\pm 4.5_{\mathrm{sys}})$ mb at the ${\Xi }^0$ 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 ${\Xi }^{-}p$ final state. This is the first study of hyperon-nucleon interactions in electron-positron collisions and opens up a new direction for such research.

Comments: 13 pages, 7 figures, with Supplemental Material