Search for B 0 meson decays into Λ and missing energy with a hadronic tagging method at Belle

Abstract

We present a search for the decays of B 0 mesons into a final state containing a Λ baryon and missing energy. These results are obtained from a 711

fb − 1 data sample that contains 772 × 10 6

B ¯ B pairs and was collected near the Υ ( 4 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e − collider. We use events in which one B meson is fully reconstructed in a hadronic decay mode and require the remainder of the event to consist of only a single Λ . No evidence for these decays is found, and we set 90% confidence level upper limits on the branching fractions in the range 2.1 – 3.8 × 10 − 5 . This measurement provides the world’s most restrictive limits, with implications for baryogenesis and dark matter production.