First measurement of Σ+⁢𝑛→Λ⁢𝑝 and Σ+⁢𝑛→Σ0⁢𝑝 cross sections via Σ+-nucleus scattering at an electron-positron collider

Using \left(1.0087\pm 0.0044\right)\times {10}^{10}J/\psi events collected with the BESIII detector at the BEPCII storage ring, the reactions Λ+n→Λ+pand \Lambda +n\rightarrow {\Sigma }^{0}+pare studied, where the Λbaryon is produced in the process J/\psi \rightarrow \Lambda \bar{\Lambda }, and the neutron is a component of the {}^{9}Be, {}^{12}C, and {}^{197}Au nuclei in the beam pipe. Clear signals of these two reactions are observed for the first time. Their cross sections are measured to be \sigma \left(\Lambda +{}^{9}\mathrm{Be}\rightarrow \Lambda +p+X\right)=\left(45.2\pm {12.1}_{\mathrm{stat}}\pm {7.2}_{\mathrm{sys}}\right)\text{\ }\mathrm{mb} and \sigma \left(\Lambda +{}^{9}\mathrm{Be}\rightarrow {\Sigma }^{0}+p+X\right)=\left(29.8\pm {9.7}_{\mathrm{stat}}\pm {6.9}_{\mathrm{sys}}\right)\text{\ }\mathrm{mb}, for an average Λmomentum of 0.992 GeV/c, within a range of ±0.015GeV/c, where Xrepresents the residual nucleus. This is the first study of Λ-nucleon scattering at an electron-positron collider. The measured results provide important input for improving our understanding of hyperon-nucleon interactions and also constitute a significant step toward resolving the "hyperon puzzle" in neutron stars.