https://doi.org/10.1140/epjc/s10052-015-3630-3
Regular Article - Theoretical Physics
Uncertainties on 
in the MMHT2014 global PDF analysis and implications for SM predictions
1
Department of Physics and Astronomy, University College London, London, WC1E 6BT, UK
2
Institute for Particle Physics Phenomenology, Durham University, Durham, DH1 3LE, UK
* e-mail: thorne@hep.ucl.ac.uk
Received:
25
June
2015
Accepted:
17
August
2015
Published online:
21
September
2015
We investigate the uncertainty in the strong coupling 
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 
scheme. We study the constraints on 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 
production allows us to explore the correlation between the mass 
of the top quark and . We find that the best-fit values are 
and 
at NLO and NNLO, respectively, with the central values changing to 
and 0.1178 when the world average of is used as a data point. We investigate the interplay between the uncertainties on 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 can be provided independently and be combined.
© SIF and Springer-Verlag Berlin Heidelberg, 2015
