title: Uncertainties on [Formula: see text] in the MMHT2014 global PDF analysis and implications for SM predictions.
abstract: We investigate the uncertainty in the strong coupling [Formula: see text] when allowing it to be a free parameter in the recent MMHT global analyses of deep-inelastic and related hard scattering data that was undertaken to determine the parton distribution functions (PDFs) of the proton. The analysis uses the standard framework of leading twist fixed-order collinear factorisation in the [Formula: see text] scheme. We study the constraints on [Formula: see text] coming from individual data sets by repeating the NNLO and NLO fits spanning the range 0.108 to 0.128 in units of 0.001, making all PDFs sets available. The inclusion of the cross section for inclusive [Formula: see text] production allows us to explore the correlation between the mass [Formula: see text] of the top quark and [Formula: see text]. We find that the best-fit values are [Formula: see text] and [Formula: see text] at NLO and NNLO, respectively, with the central values changing to [Formula: see text] and 0.1178 when the world average of [Formula: see text] is used as a data point. We investigate the interplay between the uncertainties on [Formula: see text] and on the PDFs. In particular we calculate the cross sections for key processes at the LHC and show how the uncertainties from the PDFs and from [Formula: see text] can be provided independently and be combined.
authors.affiliation: Department of Physics and Astronomy, University College London, London, WC1E 6BT UK.
authors.forename: L A
authors.initials: LA
authors.lastname: Harland-Lang
authors.affiliation: Institute for Particle Physics Phenomenology, Durham University, Durham, DH1 3LE UK.
authors.forename: A D
authors.initials: AD
authors.lastname: Martin
authors.affiliation: Department of Physics and Astronomy, University College London, London, WC1E 6BT UK.
authors.forename: P
authors.initials: P
authors.lastname: Motylinski
authors.affiliation: Department of Physics and Astronomy, University College London, London, WC1E 6BT UK.
authors.forename: R S
authors.initials: RS
authors.lastname: Thorne