Revisiting $\mathbf{Vh(\rightarrow b \bar b)}$ at the LHC and FCC-hh

TL;DR

This paper improves the analysis of Vh production with h→bb decay at hadron colliders, enhancing sensitivity to SMEFT operators and providing competitive bounds on new physics scales at LHC and FCC-hh.

Contribution

It introduces a combined analysis of boosted and resolved categories with a scale-invariant b-tagging algorithm, improving bounds on EFT operators and new physics scales.

Findings

Sensitivity to 4 SMEFT operators modifies W/Z couplings.

Combining categories improves bounds by up to 17%.

Bounds on new physics scale reach 20 TeV at FCC-hh.

Abstract

Diboson production processes provide good targets for precision measurements at present and future hadron colliders. We consider $Vh$ production, focusing on the $h \to b\bar b$ decay channel, whose sizeable cross section makes it accessible at the LHC. We perform an improved analysis by combining the 0-, 1- and 2-lepton channels with a scale-invariant $b$-tagging algorithm that allows us to exploit events with either a boosted Higgs via mass-drop tagging or resolved $b$-jets. This strategy gives sensitivity to 4 dimension-6 SMEFT operators that modify the $W$ and $Z$ couplings to quarks and is competitive with the bounds obtained from global fits. The benefit of the $h\to b\bar b$ decay channel is the fact that it is the only $Vh$ channel accessible at the LHC Run 3 and HL-LHC, while at FCC-hh it is competitive with the effectively background-free $h\to \gamma\gamma$ channel assuming $\lesssim 5$% systematic uncertainty. Combining the boosted and resolved categories yields a 17% improvement on the most strongly bounded Wilson coefficient at the LHC Run 3 with respect to the boosted category alone (and a 7% improvement at FCC-hh). We also show that, at FCC-hh, a binning in the rapidity of the $Vh$ system can significantly reduce correlations between some EFT operators. The bounds we obtain translate to a lower bound on the new physics scale of $5$, $8$, and $20$ TeV at the LHC Run 3, HL-LHC, and FCC-hh respectively, assuming new-physics couplings of order unity. Finally, we assess the impact of the $Vh$ production channel on anomalous triple gauge coupling measurements, comparing with their determination at lepton colliders.