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Uncertainties on αSαS in the MMHT2014 global PDF analysis and implications for SM predictions

Harland-Lang, L.A.; Martin, A.D.; Motylinski, P.; Thorne, R.S.

Uncertainties on αSαS in the MMHT2014 global PDF analysis and implications for SM predictions Thumbnail


Authors

L.A. Harland-Lang

P. Motylinski

R.S. Thorne



Abstract

We investigate the uncertainty in the strong coupling αS(M2Z)αS(MZ2) 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 MS¯¯¯¯¯¯¯MS¯ scheme. We study the constraints on αS(M2Z)αS(MZ2) 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 tt¯tt¯ production allows us to explore the correlation between the mass mtmt of the top quark and αS(M2Z)αS(MZ2) . We find that the best-fit values are αS(M2Z)=0.1201±0.0015αS(MZ2)=0.1201±0.0015 and 0.1172±0.00130.1172±0.0013 at NLO and NNLO, respectively, with the central values changing to αS(M2Z)=0.1195αS(MZ2)=0.1195 and 0.1178 when the world average of αS(M2Z)αS(MZ2) is used as a data point. We investigate the interplay between the uncertainties on αS(M2Z)αS(MZ2) 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 αS(M2Z)αS(MZ2) can be provided independently and be combined.

Citation

Harland-Lang, L., Martin, A., Motylinski, P., & Thorne, R. (2015). Uncertainties on αSαS in the MMHT2014 global PDF analysis and implications for SM predictions. The European Physical Journal C, 75(9), Article 435. https://doi.org/10.1140/epjc/s10052-015-3630-3

Journal Article Type Article
Acceptance Date Aug 17, 2015
Online Publication Date Sep 21, 2015
Publication Date Sep 21, 2015
Deposit Date May 25, 2017
Publicly Available Date May 31, 2017
Journal European Physical Journal C: Particles and Fields
Print ISSN 1434-6044
Electronic ISSN 1434-6052
Publisher SpringerOpen
Peer Reviewed Peer Reviewed
Volume 75
Issue 9
Article Number 435
DOI https://doi.org/10.1140/epjc/s10052-015-3630-3
Public URL https://durham-repository.worktribe.com/output/1358369

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Publisher Licence URL
http://creativecommons.org/licenses/by/4.0/

Copyright Statement
© The Author(s) 2015 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Funded by SCOAP3.






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