https://doi.org/10.1140/epjc/s10052-010-1462-8
Heavy-quark mass dependence in global PDF analyses and 3- and 4-flavour parton distributions
1
Institute for Particle Physics Phenomenology, University of Durham, Durham, DH1 3LE, UK
2
Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
3
Department of Physics and Astronomy, University College London, London, WC1E 6BT, UK
4
Theory Group, Physics Department, CERN, 1211, Geneva 23, Switzerland
Received:
16
July
2010
Revised:
30
August
2010
Published online:
19
October
2010
We study the sensitivity of our recent MSTW 2008 NLO and NNLO PDF analyses to the values of the charm- and bottom-quark masses, and we provide additional public PDF sets for a wide range of these heavy-quark masses. We quantify the impact of varying m
c
and m
b
on the cross sections for W, Z and Higgs production at the Tevatron and the LHC. We generate 3- and 4-flavour versions of the (5-flavour) MSTW 2008 PDFs by evolving the input PDFs and α
S
determined from fits in the 5-flavour scheme, including the eigenvector PDF sets necessary for calculation of PDF uncertainties. As an example of their use, we study the difference in the Z total cross sections at the Tevatron and LHC in the 4- and 5-flavour schemes. Significant differences are found, illustrating the need to resum large logarithms in 
by using the 5-flavour scheme. The 4-flavour scheme is still necessary, however, if cuts are imposed on associated (massive) b-quarks, as is the case for the experimental measurement of 
production and similar processes.
© Springer-Verlag / Società Italiana di Fisica, 2010
