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arXiv · 1007.2624

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

A. D. Martin·W. J. Stirling·R. S. Thorne·G. Watt
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Abstract

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 alpha_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 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 Z b bbar production and similar processes.

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A. D. Martin, W. J. Stirling, R. S. Thorne, G. Watt. 2010-11-22. Heavy-quark mass dependence in global PDF analyses and 3- and 4-flavour parton distributions. https://doi.org/10.1140/epjc%2Fs10052-010-1462-8

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