https://doi.org/10.1140/epjc/s10052-021-09057-0
Regular Article – Theoretical Physics
Parton distributions from LHC, HERA, Tevatron and fixed target data: MSHT20 PDFs
1
Rudolf Peierls Centre, Beecroft Building, Parks Road, OX1 3PU, Oxford, UK
2
Department of Physics and Astronomy, University College London, WC1E 6BT, London, UK
3
Institute for Particle Physics Phenomenology, Durham University, DH1 3LE, Durham, UK
c
lucian.harland-lang@physics.ox.ac.uk
Received:
22
December
2020
Accepted:
15
March
2021
Published online:
21
April
2021
We present the new MSHT20 set of parton distribution functions (PDFs) of the proton, determined from global analyses of the available hard scattering data. The PDFs are made available at NNLO, NLO, and LO, and supersede the MMHT14 sets. They are obtained using the same basic framework, but the parameterisation is now adapted and extended, and there are 32 pairs of eigenvector PDFs. We also include a large number of new data sets: from the final HERA combined data on total and heavy flavour structure functions, to final Tevatron data, and in particular a significant number of new LHC 7 and 8 TeV data sets on vector boson production, inclusive jets and top quark distributions. We include up to NNLO QCD corrections for all data sets that play a major role in the fit, and NLO EW corrections where relevant. We find that these updates have an important impact on the PDFs, and for the first time the NNLO fit is strongly favoured over the NLO, reflecting the wider range and in particular increased precision of data included in the fit. There are some changes to central values and a significant reduction in the uncertainties of the PDFs in many, though not all, cases. Nonetheless, the PDFs and the resulting predictions are generally within one standard deviation of the MMHT14 results. The major changes are the 
valence quark difference at small x, due to the improved parameterisation and new precise data, the 
difference at small x, due to a much improved parameterisation, and the strange quark PDF due to the effect of LHC W, Z data and inclusion of new NNLO corrections for dimuon production in neutrino DIS. We discuss the phenomenological impact of our results, and in general find reduced uncertainties in predictions for processes such as Higgs, top quark pair and W, Z production at post LHC Run-II energies.
We dedicate this paper to the memory of James Stirling and Dick Roberts, both of whom sadly died in the past 2 years. They were founding members of the collaboration of our PDF global analyses, which started with the presentation of the first ever NLO PDF sets in 1987.
© The Author(s) 2021
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