Precision from the diphoton Zh channel at FCC-hh

TL;DR

This paper evaluates the potential of the 100 TeV FCC-hh collider to measure SMEFT operators via the diphoton Zh channel, demonstrating improved bounds over HL-LHC and future lepton colliders, especially for certain operators.

Contribution

It provides the first detailed sensitivity analysis of the diphoton Zh channel at FCC-hh for constraining SMEFT operators related to gauge boson couplings.

Findings

Sensitivity to $ ext{O}_{ ext{phi q}}^{(3)}$ is high.

Binning in $Zh$ rapidity improves bounds on $ ext{O}_{ ext{phi q}}^{(1)}$.

Projected bounds surpass HL-LHC and are competitive with other FCC-hh channels.

Abstract

The future 100 TeV FCC-hh hadron collider will give access to rare but clean final states which are out of reach of the HL-LHC. One such process is the $Zh$ production channel in the $(\nu\bar{\nu} / \ell^{+}\ell^{-})\gamma\gamma$ final states. We study the sensitivity of this channel to the $\mathcal{O}_{\varphi q}^{(1)}$, $\mathcal{O}_{\varphi q}^{(3)}$, $\mathcal{O}_{\varphi u}$, and $\mathcal{O}_{\varphi d}$ SMEFT operators, which parametrize deviations of the $W$ and $Z$ couplings to quarks, or, equivalently, anomalous trilinear gauge couplings (aTGC). While our analysis shows that good sensitivity is only achievable for $\mathcal{O}_{\varphi q}^{(3)}$, we demonstrate that binning in the $Zh$ rapidity has the potential to improve the reach on $\mathcal{O}_{\varphi q}^{(1)}$. Our estimated bounds are one order of magnitude better than projections at HL-LHC and is better than global fits at future lepton colliders. The sensitivity to $\mathcal{O}_{\varphi q}^{(3)}$ is competitive with other channels that could probe the same operator at FCC-hh. Therefore, combining the different diboson channels sizeably improves the bound on $\mathcal{O}_{\varphi q}^{(3)}$, reaching a precision of $|\delta g_{1z}| \lesssim 2 \times 10^{-4}$ on the deviations in the $ZWW$ interactions.