$B \to K \nu\bar\nu$, MiniBooNE and muon $g-2$ anomalies from a dark sector

Abstract

Belle II has reported the first evidence for $B^+ \to K^+\nu\bar\nu$ with a branching ratio $2.7 \sigma$ higher than the standard model expectation. We explain this, and the MiniBooNE and muon anomalous magnetic moment anomalies in a model with a dark scalar that couples to a slightly heavier sterile Dirac neutrino and that communicates with the visible sector via a Higgs portal. We make predictions for rare kaon and other $B$ meson decays.