First Study of Reaction Ξ^{0}n→Ξ^{-}p Using Ξ^{0}-Nucleus Scattering at an Electron-Positron Collider

Using (1.0087 & PLUSMN; 0.0044) x 1010 J=iy events collected with the BESIII detector at the BEPCII storage ring, the process E0n & RARR; E-p is studied, where the E0 baryon is produced in the process J=iy & RARR; E0E over bar 0 and the neutron is a component of the 9Be, 12C, and 197Au nuclei in the beam pipe. A clear signal is observed with a statistical significance of 7.1u. The cross section of the reaction E0 + 9Be & RARR; E- + p + 8Be is determined to be u(E0 + 9Be & RARR; E- + p + 8Be) = (22.1 & PLUSMN; 5.3stat & PLUSMN; 4.5sys) mb at the E0 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 E-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.