Impact of low-$x$ resummation on QCD analysis of HERA data

Abstract

Fits to the final combined HERA deep-inelastic scattering cross-section data within the conventional DGLAP framework of QCD have shown some tension at low $x$ and low $Q^2$. A resolution of this tension incorporating $\ln (1/x)$-resummation terms into the HERAPDF fits is investigated using the xFitter program. The kinematic region where this resummation is important is delineated. Such high-energy resummation not only gives a better description of the data, particularly of the longitudinal structure function $F_L$, it also results in a gluon PDF which is steeply rising at low $x$ for low scales, $Q^2\simeq 2.5$ GeV${}^2$, contrary to the fixed-order NLO and NNLO gluon PDF.

Comments: 14 pages, 12 figures. Additional studies and various improvements. EPJC version