Probing the $R_{K^{(\ast )}}$ Anomaly at a Muon Collider

Abstract

The LHCb measurements of the $\mu /e$ ratio in $B\to K\ell \ell$ decays $(R_{K^{}})$ indicate a deficit with respect to the Standard Model prediction, supporting earlier hints of lepton universality violation observed in the $R_{K^{(\ast )}}$ ratio. Possible explanations of these $B$-physics anomalies include heavy $Z^{\prime }$ bosons or scalar and vector leptoquarks mediating $b\to s{\mu }^{+}{\mu }^{-}$. We note that a muon collider can directly measure this process via ${\mu }^{+}{\mu }^{-}\to b\bar{s}$ and can shed light on the lepton non-universality scenario. Investigating currently discussed center-of-mass energies $\sqrt{s}=3$, 6 and 10 TeV, we show that the parameter space of $Z^{\prime }$ and leptoquark solutions to the $R_{K^{(\ast )}}$ anomalies can be mostly covered. Effective operators explaining the anomalies can be probed with the muon collider setup $\sqrt{s}=6\mathrm{TeV}$ and integrated luminosity $L=4\mathrm{a}{\mathrm{b}}^{-1}$.

Comments: 8 pages + references, 5 figures, matches published version