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

By A. Martin, W. Stirling, R. Thorne, Graeme Watt. 2010

171 citations recorded by the source corpus.

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.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/2a61dde19367a5d9708f36e2a9bb19dc973c0bb0

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Nuclear and High Energy Physics

Citations in the corpus

A Large Hadron Electron Collider at CERN: Report on the Physics and Design Concepts for Machine and Detector (2012, methodology): “[138] used the pole mass as a free parameter and finds mc = 1.”
b-initiated processes at the LHC: a reappraisal (2012, background): “In this respect it is not surprising that 5F scheme calculations of total cross sections for bb̄ fusion into Higgs or Z leads to very stable results under scale variations [73].”
Les Houches 2013: Physics at TeV Colliders: Standard Model Working Group Report (2014, background): “Dependence on parameters of the heavy-quark schemes and mass of the charm quark has been studied before [160, 239, 256, 257], and relatively small impact on the gluon PDF at a fixed αs has been observed.”
Measurement of the inclusive W and Z production cross sections in pp collisions at $ \sqrt {s} = 7 $ TeV with the CMS experiment (2011, result): “The uncertainties, at 68% CL, include contributions from the strong coupling αS [60, 61], the choice of heavy quark masses (charm and bottom quarks) [62] as well as neglected higher-order corrections beyond NNLO, by allowing the renormalization and factorization scales to vary in a similar way to th”
A critical appraisal and evaluation of modern PDFs (2016, methodology): “1 [234,235], MSTW [231] and MMHT [236] obtained the range αs(MZ ) = 0.1171 − 0.1174.”
Handbook of LHC Higgs Cross Sections: 3. Higgs Properties (2013, methodology): “We adopt the CT10 [1 45], MRST [727] and NNPDF21 [210] 4FS pdf sets.”
Automatic spin-entangled decays of heavy resonances in Monte Carlo simulations (2012, unknown): “4) instead [24], where αS(MZ) = 0.”