When energy goes missing: new physics in b→ s νν with sterile neutrinos

Belle II recently reported the first measurement of B^+→ K^+ + inv , which is 2.8σ above the Standard Model prediction. We explore the available parameter space of new physics within Standard Model effective field theory extended by sterile neutrinos ( ν SMEFT) and provide predictions for the other B→ K^(⋆ ) +inv decay modes and invisible B_s decays. We also briefly comment on charged current decays B→ D^(⋆ )ℓν̅ and possible ultraviolet completions of the relevant ν SMEFT operators.