We briefly summarise the "MSTW 2008" determination of parton distribution functions (PDFs), and subsequent follow-up studies, before reviewing some topical issues concerning the PDF dependence of cross sections at the Tevatron and LHC. We update a recently published study of benchmark Standard Model total cross sections (W,Z,gg→H and tt̄ production) at the 7 TeV LHC, where we account for all publicly available PDF sets and we compare to LHC data for W, Z, and tt̄ production. We show the sensitivity of the Higgs cross sections to the gluon distribution, then we demonstrate the ability of the Tevatron jet data, and also the LHC tt̄ data, to discriminate between PDF sets with different high-x gluon distributions. We discuss the related problem of attempts to extract the strong coupling αS from only deep-inelastic scattering data, and we conclude that a direct data constraint on the high-x gluon distribution is required to obtain a meaningful result. We therefore discourage the use of PDF sets obtained from "non-global" fits where the high-x gluon distribution is not directly constrained by data.
Nuclear Physics B Proceedings Supplements
- Pub Date:
- January 2012
- High Energy Physics - Phenomenology
- 20 pages, 16 figures. To appear in the proceedings of the Ringberg Workshop on "New Trends in HERA Physics 2011", Ringberg Castle, Tegernsee, Germany, 25-28 September 2011