Author(s): M. Ablikim et al. (BESIII Collaboration) Using $(10\text{ }087±44)×{10}^{6}\text{ }\text{ }J/ψ$ events collected with the BESIII detector, we study the semileptonic decay ${\mathrm{Ξ}}^{−}→\mathrm{Λ}{e}^{−}{\overline{ν}}_{e}$ for the first time at an electron-positron collider. The absolute branching fraction is determined for the first ti… [Phys. Rev. Lett. 137, 091801] Published Mon Aug 24, 2026