LHC di-lepton searches for Z′ bosons which explain measurements of b → sl+l− transitions

Several current measurements of $b\to s{l}^{+}{l}^{-}$ processes are in tension with Standard Model predictions, whereas others (e.g. $R_K$ and $R_{K^{⁎}}$) are in reasonable agreement with them. We examine some recent $Z^{\prime }$ models that fit the data as a whole appreciably better than does the Standard Model, confronting the models with ATLAS resonance searches in the $e^{+}{e}^{-}$ and ${\mu }^{+}{\mu }^{-}$ channels. The models are constrained by both channels; we find that the searches rule out less than one fifth of the allowed range of $M_{Z^{\prime }}$. We estimate that the HL-LHC can roughly double the current sensitivity in $M_{Z^{\prime }}$, but to cover the whole of the parameter space would take a more powerful machine, such as a 100 TeV pp collider.