A sensitive search for the lepton-number-violating decay Ξ-→pμ-μ- has been performed using a sample of ∼109 Ξ- hyperons produced in 800 GeV/c p-Cu collisions. We obtain B(Ξ-→pμ-μ-)<4.0×10-8 at 90% confidence, improving on the best previous limit by 4 orders of magnitude.
Rajaram, D.; Holmstrom, Timothy; and HyperCP Collaboration, "Search for the Lepton-Number-Violating Decay Ξ-→pμ-μ-" (2005). Chemistry and Physics Faculty Publications. 12.
Phys. Rev. Lett. 94, 181801 (2005)