Precision from the diphoton Zh channel at FCC-hh

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 $$ \left(v\overline{v}/{\mathrm{\ell}}^{+}{\mathrm{\ell}}^{-}\right)\gamma \gamma $$ v v ¯ / ℓ + ℓ − γγ final states. We study the sensitivity of this channel to the $$ {\mathcal{O}}_{\varphi q}^{(1)},\kern0.5em {\mathcal{O}}_{\varphi q}^{(3)},\kern0.5em {\mathcal{O}}_{\varphi u} $$ O φq 1 , O φq 3 , O φu , and $$ {\mathcal{O}}_{\varphi d} $$ O φd 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 $$ {\mathcal{O}}_{\varphi q}^{(3)} $$ O φq 3 , we demonstrate that binning in the Zh rapidity has the potential to improve the reach on $$ {\mathcal{O}}_{\varphi q}^{(1)} $$ O φq 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 $$ {\mathcal{O}}_{\varphi q}^{(3)} $$ O φq 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 $$ {\mathcal{O}}_{\varphi q}^{(3)} $$ O φq 3 , reaching a precision of |δg1z| ≲ × 10−4 on the deviations in the ZWW interactions.

Diboson production in the SMEFT from gluon fusion

“…To then demonstrate in a realistic manner how the loop induced component of the diboson process plays a special role, we focus on ZH production. Previous studies of this process focused on one of the initial states, either gg or q q, and set the other to its SM value to play the role of a background [24,31,32,42]. This methodology can be justified by the fact that quark-and gluon-initiated ZH production probe disjoint sets of SMEFT dimension-6 operators.…”

“…There are no flat directions in the space of the light-quark operators and the discussion on the sensitivity to each of their Flavour-Universal versions in refs. [31,32] applies straightforwardly.…”

“…Future hadron colliders with higher centre-of-mass energies could change the previous picture. At 100 TeV, the b b channel contributes ∼ 5% of the partonic cross section of q q → ZH in the region p H T ∈ [400, 600] GeV [31]. The uncertainties on the fits and experimental measurements would be of the same order or less, so the bounds on the light-quark operators could be distinguishable from the ones on the flavour-universal ones.…”