HERA data and collinearly-improved BK dynamics

TL;DR

This paper applies a collinearly-improved BK equation with all-order resummation and running coupling corrections to fit HERA deep inelastic scattering data at small x, achieving excellent results and extending the fit to higher Q^2.

Contribution

It introduces a novel collinearly-improved BK equation using Bjorken x as the evolution variable, with resummation effects that enhance fit quality and extend applicability.

Findings

Resummation effects significantly improve fit quality.

The model fits HERA data well with reasonable parameters.

Inclusion of DGLAP-like logarithms extends fit to higher Q^2.

Abstract

Within the framework of the dipole factorisation, we use a recent collinearly-improved version of the Balitsky-Kovchegov equation to fit the HERA data for inclusive deep inelastic scattering at small Bjorken $x$. The equation includes an all-order resummation of double and single transverse logarithms and running coupling corrections. Compared to similar equations previously proposed in the literature, this work makes a direct use of Bjorken $x$ as the rapidity scale for the evolution variable. We obtain excellent fits for reasonable values for the four fit parameters. We find that the fit quality improves when including resummation effects and a physically-motivated initial condition. In particular, the resummation of the DGLAP-like single transverse logarithms has a sizeable impact and allows one to extend the fit up to relatively large photon virtuality $Q^2$.