A Variable Flavour Number Scheme for Heavy Quark Production at Small x

Abstract

We define a new variable flavour number scheme for use in deep inelastic scattering, motivated by the need to consistently implement high energy resummations alongside a fixed order QCD expansion. We define the DIS(chi) scheme at fixed order, and show how to obtain the small x coefficient functions and heavy flavour matrix elements to leading order in the high energy resummation. We then implement these results in a global fit at LO which includes leading resummations with running coupling corrections. Finally, we address the impact of the resummed results on predictions for the longitudinal structure function. We find that they stabilise the behaviour of F_L at small x. Overall, we find that resummations significantly improve the fit to scattering data in the low x regime, although higher orders in the fixed order expansion are needed to describe current structure function and related data over the complete x range.

40 pages, 16 figures

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• Predictions for high energy neutrino cross-sections from the ZEUS global PDF fits
• Next-to-leading and resummed BFKL evolution with saturation boundary
• Towards parton distribution functions with small-$x$ resummation: HELL 2.0
• Evidence for the Discrete Asymptotically-Free BFKL Pomeron from HERA Data
• The Ratio $R=F_L/F_T$ in DIS as a Probe of the Charm Content of the Proton
• The BFKL-Regge factorization and $F_2^b$, $F_2^c$, $F_L$ at HERA: physics implications of nodal properties of the BFKL eigenfunctions
• Beauty, charm and $F_L$ at HERA: new data vs. early predictions
• Quark Masses and Resummation in Precision QCD Theory
• Aspects of High Energy Scattering
• An analysis of the longitudinal structure function at next-to-leading order approximation at small-$x$
• The HERA challenges for LHC