Regular Article - Theoretical Physics
An investigation of the and heavy quark mass dependence in the MSHT20 global PDF analysis
Department of Physics and Astronomy, University College London, WC1E 6BT, London, UK
2 Rudolf Peierls Centre, Beecroft Building, Parks Road, OX1 3PU, Oxford, UK
3 Institute for Particle Physics Phenomenology, Durham University, DH1 3LE, Durham, UK
Accepted: 6 August 2021
Published online: 17 August 2021
We investigate the MSHT20 global PDF sets, demonstrating the effects of varying the strong coupling and the masses of the charm and bottom quarks. We determine the preferred value, and accompanying uncertainties, when we allow to be a free parameter in the MSHT20 global analyses of deep-inelastic and related hard scattering data, at both NLO and NNLO in QCD perturbation theory. We also study the constraints on which come from the individual data sets in the global fit by repeating the NNLO and NLO global analyses at various fixed values of , spanning the range to 0.130 in units of 0.001. We make all resulting PDFs sets available. We find that the best fit values are and at NLO and NNLO respectively. We investigate the relationship between the variations in and the uncertainties on the PDFs, and illustrate this by calculating the cross sections for key processes at the LHC. We also perform fits where we allow the heavy quark masses and to vary away from their default values and make PDF sets available in steps of and , using the pole mass definition of the quark masses. As for varying values, we present the variation in the PDFs and in the predictions. We examine the comparison to data, particularly the HERA data on charm and bottom cross sections and note that our default values are very largely compatible with best fits to data. We provide PDF sets with 3 and 4 active quark flavours, as well as the standard value of 5 flavours.
© The Author(s) 2021
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