The European Physical Journal C

, Volume 70, Issue 1, pp 51–72

Heavy-quark mass dependence in global PDF analyses and 3- and 4-flavour parton distributions


  • A. D. Martin
    • Institute for Particle Physics PhenomenologyUniversity of Durham
  • W. J. Stirling
    • Cavendish LaboratoryUniversity of Cambridge
  • R. S. Thorne
    • Department of Physics and AstronomyUniversity College London
    • Theory Group, Physics DepartmentCERN
Regular Article - Theoretical Physics

DOI: 10.1140/epjc/s10052-010-1462-8

Cite this article as:
Martin, A.D., Stirling, W.J., Thorne, R.S. et al. Eur. Phys. J. C (2010) 70: 51. doi:10.1140/epjc/s10052-010-1462-8


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 mc and mb 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 αS 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 \(Q^{2}/m_{b}^{2}\) 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 \(Zb\bar{b}\) production and similar processes.

Copyright information

© Springer-Verlag / Società Italiana di Fisica 2010