Search for baryon and lepton number violating decays of Ξ0 hyperons

Using (1.0087 pm 0.0044) × 10^10 J/ψ events collected by the BESIII detector at the BEPCII collider, we report the first search for the baryon and lepton number violating decays Ξ0 → K−e+ with Δ(B − L) = 0 and Ξ0 → K+e− with |Δ(B − L)| = 2, where B (L) is the baryon (lepton) number. While no signal is observed, the upper limits on the branching fractions of these two decays are set to B(Ξ0 → K−e+) < 3.6 × 10−6 and B(Ξ0 → K+e−) < 1.9 × 10−6 at the 90% confidence level, respectively. These results offer a direct probe of baryon number violating interactions involving a strange quark.