The Case for Future Hadron Colliders From $B \to K^{(*)} \mu^+ \mu^-$ Decays

TL;DR

This paper evaluates the potential of future high-energy hadron colliders to discover new particles like $Z'$ bosons and leptoquarks that could explain anomalies observed in $B o K^{(*)} \mu^+\mu^-$ decays, suggesting that upcoming colliders could probe significant portions of the relevant parameter space.

Contribution

It provides a detailed sensitivity analysis of future colliders for detecting particles responsible for $B$ decay anomalies, highlighting their discovery potential.

Findings

Future colliders can cover most of the $Z'$ parameter space up to 8 TeV in mass.

A 100 TeV collider can detect leptoquarks up to 12-21 TeV depending on coupling strength.

FCC-hh can potentially explain all current anomalies with leptoquark masses up to 41 TeV.

Abstract

Recent measurements in $B \to K^{(*)} \mu^+ \mu^-$ decays are somewhat discrepant with Standard Model predictions. They may be harbingers of new physics at an energy scale potentially accessible to direct discovery. We estimate the sensitivity of future hadron colliders to the possible new particles that may be responsible for the anomalies: leptoquarks or $Z^\prime$s. We consider luminosity upgrades for a 14 TeV LHC, a 33 TeV LHC, and a 100 TeV $pp$ collider such as the FCC-hh. Coverage of $Z^\prime$ models is excellent: for narrow particles, with perturbative couplings that may explain the $b$-decay results for $Z^\prime$ masses up to 20 TeV, a 33 TeV 1 ab$^{-1}$ LHC is expected to cover most of the parameter space up to 8 TeV in mass, whereas the 100 TeV FCC-hh with 10 ab$^{-1}$ will cover all of it. A smaller portion of the leptoquark parameter space is covered by future colliders: for example, in a $\mu^+\mu^-jj$ di-leptoquark search, a 100 TeV 10 ab$^{-1}$ collider has a projected sensitivity up to leptoquark masses of 12 TeV (extendable to 21 TeV with a strong coupling for single leptoquark production), whereas leptoquark masses up to 41 TeV may in principle explain the anomalies.