Scrutinizing Dark-Matter Scenarios with B → (K,K∗)ν¯ν Decays

Conceivable explanations of Belle-II measurements of a (surprising) excess of missing energy decays of the B meson to the K meson not covered by standard model neutrino–antineutrino pairs might be offered by additional contributions of dark matter fermion–antifermion pairs. Assuming the excessive missing-energy events to be mediated by a (generic) scalar or vector boson, a simultaneous inspection of both the missing energy B decays into a pseudoscalar K meson or a vector K∗ meson enables to gain information on the nature of any boson relating the standard-model and dark-matter sectors, irrespective of (unknown) dark-sector details. Upon availability of indispensable experimental data, most prominent among such insights might be the identification of the mediator spin from the differential B-meson decay widths.