Parameters of dark matter in B-meson decays

A possible answer to the question of why a peculiar excess of missing-energy decays of the 𝐵 meson to the 𝐾 meson (compared to the rate predicted by accounting for the decays which involve neutrino-antineutrino pair production allowed by the Standard Model) was observed in the Belle II experiment may be given by taking into account additional contributions from hidden sector (and, in particular, dark matter) pair production. Assuming the excess missing-energy events are due to processes involving a mediator — a generic scalar or vector boson, one may conduct a parallel inspection of the 𝐵 decay to the pseudoscalar 𝐾 meson as well as to the vector 𝐾∗ meson (in both cases, a missing-energy process), which will allow one to determine the parameters of bosons relating Standard Model particles to those of the hidden sector irrespective of any (unknown as of yet) details concerning the structure of this hidden sector itself. Such parameters, which it will be possible to ascertain upon the emergence of new experimental data, include, first of all, the mediator spin, which can be identified from the differential 𝐵 meson decay widths.