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

Abstract

Using $(1.0087\pm 0.0044)\times 10^{10}$ $J/\ddot{I}ˆ$ events collected with the BESIII detector at the BEPCII storage ring, the process $\hat{I}{ž}^{0}n\to \hat{I}{ž}^{-}p$ is studied, where the $\hat{I}{ž}^0$ baryon is produced in the process $J/\ddot{I}ˆ\to \hat{I}{ž}^0\bar{\hat{I}}{ž}^0$ 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 $7.1\ddot{I}ƒ$. The cross section of the reaction $\hat{I}{ž}^0+{}^9\mathrm{Be}\to \hat{I}{ž}^{-}+p+{}^8\mathrm{Be}$ is determined to be $\ddot{I}ƒ(\hat{I}{ž}^0+{}^9\mathrm{Be}\to \hat{I}{ž}^{-}+p+{}^8\mathrm{Be})=(22.1\pm 5.3_{\mathrm{stat}}\pm 4.5_{\mathrm{sys}})$ mb at the $\hat{I}{ž}^0$ 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 $\hat{I}{ž}^{-}p$ final state. This is the first study of hyperon-nucleon interactions in electron-positron collisions and opens up a new direction for such research.

13 pages, 7 figures, with Supplemental Material