MMHT

MMHT refers to a set of parton distribution functions (PDFs) for the proton produced by the MMHT collaboration, comprising Martin, Motylinski, Harland-Lang and Thorne. These PDFs describe the probability of finding partons carrying a fraction x of the proton’s momentum at a given energy scale Q^2, for gluons and the light and heavy quarks, and are used as essential inputs in perturbative quantum chromodynamics calculations of high-energy processes at hadron colliders.

The MMHT sets are the successor to the MSTW/MSTW2008 PDFs; MMHT is an acronym based on the surnames of the authors. The main release, MMHT2014, incorporated new data and methodological refinements and has since served as a standard reference in collider phenomenology. The collaboration provides PDFs for multiple perturbative orders, including leading, next-to-leading, and next-to-next-to-leading order, and they apply a generalized heavy-quark treatment via a variable-flavor-number scheme.

Methodologically, MMHT performs global fits to a wide range of experimental data, parameterizes PDFs at an initial scale, and evolves them with the DGLAP equations. Uncertainties are estimated and supplied through Hessian eigenvector sets, allowing users to propagate PDF errors to predictions.

Data inputs span deep inelastic scattering measurements from HERA and fixed-target experiments, as well as collider data from Drell-Yan production, jet measurements, and W/Z and top-quark production at the Tevatron and the LHC. The resulting PDFs are designed to be robust across a broad kinematic range in x and Q^2.

Availability and use: MMHT PDFs are distributed through the LHAPDF library and are widely employed in theoretical predictions for collider phenomenology, including Higgs production, vector boson processes, and jet cross sections, with associated PDF uncertainties.

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