gluonfusion

Gluon fusion is a process in quantum chromodynamics by which two gluons interact to produce a heavy system, most notably the Higgs boson. In the Standard Model, gluons couple to the Higgs boson only indirectly through heavy quark loops, with the top quark providing the dominant contribution to the leading amplitude.

Because the initial-state gluons carry color, the process is purely strong and is highly sensitive to higher-order QCD corrections. The leading order is loop-induced, with the top-quark triangle mediating gg to H. At high energies, the rate can be described by an effective field theory in which the top quark is integrated out, yielding a direct effective coupling between two gluons and the Higgs, a simplification that facilitates calculation of higher-order corrections.

Gluon fusion is the dominant production mechanism for the Higgs boson in proton-proton collisions at the Large Hadron Collider, accounting for the majority of observed Higgs events at center-of-mass energies of 7 to 13 TeV. Production can occur in association with jets, such as gg → H + jets, which helps probe the structure of the interaction and its kinematic properties.

Calculations include QCD corrections up to very high orders, with next-to-next-to-leading order and beyond, and soft-gluon resummation improving precision. Uncertainties arise from renormalization and factorization scales, parton distribution functions, and the value of the strong coupling constant αs. These theoretical uncertainties are a major component of the overall uncertainty in the predicted Higgs production rate.

Beyond the Standard Model, additional heavy particles in the loop or new interactions could modify the gluon-fusion rate, making precision measurements of this process a key probe of the Higgs sector and potential new physics.