Search for $B^0$ meson decays into $\Lambda$ 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 $\Lambda$ baryon and missing energy. These results are obtained from a $711{\text{fb}}^{-1}$ data sample that contains $772\times 10^6$ $B\overline{B}$ pairs and was collected near the ${\rm Y}(4S)$ 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 $\Lambda$. No evidence for these decays is found and we set $90\%$ confidence level upper limits on the branching fractions in the range $2.1$-$3.8\times 10^{-5}$. This measurement provides the world's most restrictive limits, with implications for baryogenesis and dark matter production.

arXiv comment8 pages, 4 figures

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• The Strange Physics of Dark Baryons