Probing B-Anomalies via Dimuon Tails at a Future Collider

We investigate the sensitivity of future proton-proton colliders to a contact interaction of the form $1/\Lambda^2 (\bar b_L \gamma_\mu s_L)(\bar \mu_L \gamma^\mu \mu_L)$ as indicated by the long-standing rare $B$-decay anomalies. We include NLO QCD and electroweak effects and employ an optimized binning scheme, and carefully validate our background calculation against ATLAS and CMS data. We find that the FCC-hh with $40$ ab$^{-1}$ of luminosity is able to exclude scales $\Lambda$ up to 26 TeV at $95 \%$ CL, and discover $\Lambda$ up to 20 TeV. While this is not quite enough to exclude or discover the current best-fit value of $39$ TeV, this can in principle be achieved with more luminosity and/or higher energy, as we study quantitatively. Our analysis is conservative in that it assumes only a $\bar b s \mu \mu$ contact interaction.