Absorptive effects and power corrections in low $x$ DGLAP evolution

TL;DR

This paper investigates the impact of absorptive effects and power corrections on the low $x$, low $Q^2$ behavior of parton densities, revealing a more accurate description of the gluon density within the DGLAP framework.

Contribution

It introduces a method to exclude absorptive effects from deep inelastic data, resulting in a revised low $x$ gluon density consistent with linear DGLAP evolution.

Findings

Revised low $x$ gluon density aligns with linear DGLAP.

Absorptive corrections significantly affect low $x$ behavior.

Power corrections lead to a flat low $x$ gluon density.

Abstract

We address a long standing problem concerning the scale behaviour of parton densities in the low $x$, low $Q^2$ domain. We emphasize the important role of absorptive corrections at low $x$ and use knowledge of diffractive deep inelastic scattering to exclude the absorptive effect from conventional deep inelastic data. In this way we obtain a significantly different low $x$ behaviour of the gluon density, which is now much better described by linear DGLAP evolution. Accounting also for a second power correction, which arises from the freezing of $\alpha_s$ at low $Q^2$, leads to an essentially flat behaviour of the low $x$ gluon density.