A first extraction of gluon TMDs from Higgs data at the LHC

Abstract

We present the first extraction of the unpolarised gluon transverse-momentum-dependent (TMD) parton distribution from Higgs-boson production data at the LHC within the framework of TMD factorisation. The analysis is based on the currently available set of ATLAS and CMS measurements of the Higgs $q_T$ distribution at $\sqrt{s}=8$ and $13$ TeV in the diphoton and four-lepton decay channels, restricted to the small-$q_T$ region where TMD factorisation is applicable. Theoretical predictions are computed up to N${}^3$LL accuracy, with the contribution of the linearly polarised gluon TMD $h_1^{\perp g}$ accounted for. Fiducial selections are consistently incorporated for both two- (diphoton) and four-body (four-lepton) final states. The fit reproduces both the shape and the normalisation of the experimental data, and yields a moderate sensitivity to the nonperturbative content of gluon TMDs. We further assess the convergence of the perturbative expansion and the stability of the extracted distribution under variations of the $q_T$ cut. This analysis provides a baseline for future extractions combining LHC Higgs measurements with other gluon-sensitive processes spanning a broader range of hard scales.