$R({K^{(*)}})$ from dark matter exchange

Abstract

Hints of lepton flavor violation have been observed by LHCb in the rate of the decay $B\to K\mu^+\mu^-$ relative to that of $B\to K e^+e^-$. This can be explained by new scalars and fermions which couple to standard model particles and contribute to these processes at loop level. We explore a simple model of this kind, in which one of the new fermions is a dark matter candidate, while the other is a heavy vector-like quark and the scalar is an inert Higgs doublet. We explore the constraints on this model from flavor observables, dark matter direct detection, and LHC run II searches, and find that, while currently viable, this scenario will be directly tested by future results from all three probes.Comment: 6 pages, 6 figures; v2: added references, changed to Majorana dark matter, direct detection constraints weakened; v3: added references, lepton flavor constraints weakened by including crossed box diagrams in fig. 1; published versio