Hadron Collider Sensitivity to Fat Flavourful $Z^\prime$s for $R_{K^{(\ast)}}$

TL;DR

This paper evaluates the potential of current and future hadron colliders to detect or constrain a hypothetical $Z^\u200b$' boson that could explain lepton flavor non-universality in B meson decays, considering various collider energies and decay widths.

Contribution

It extends previous collider sensitivity analyses to include sizeable decay widths and compares sensitivities across HL-LHC, HE-LHC, and FCC for $Z^\u200b$' detection.

Findings

HL-LHC can detect narrow $Z^\u200b$' resonances consistent with anomalies.

FCC could probe $Z^\u200b$' masses up to 23 TeV with large widths.

FCC covers the entire perturbative parameter space for the models considered.

Abstract

We further investigate the case where new physics in the form of a massive $Z^\prime$ particle explains apparent measurements of lepton flavour non-universality in $B \rightarrow K^{(\ast)} l^+ l^-$ decays. Hadron collider sensitivities for direct production of such $Z^\prime$s have been previously studied in the narrow width limit for a $\mu^+ \mu^-$ final state. Here, we extend the analysis to sizeable decay widths and improve the sensitivity estimate for the narrow width case. We estimate the sensitivities of the high luminosity 14 TeV Large Hadron Collider (HL-LHC), a high energy 27 TeV LHC (HE-LHC), as well as a potential 100 TeV future circular collider (FCC). The HL-LHC has sensitivity to narrow $Z^\prime$ resonances consistent with the anomalies. In one of our simplified models the FCC could probe 23 TeV $Z^\prime$ particles with widths of up to 0.35 of their mass at 95\% confidence level (CL). In another model, the HL-LHC and HE-LHC cover sizeable portions of parameter space, but the whole of perturbative parameter space can be covered by the FCC.