The Unpolarized Gluon Anomalous Dimension at Small x

TL;DR

This paper analyzes the impact of small-x resummation on gluon anomalous dimensions, revealing significant negative effects on the gluon splitting function at low x, with implications for high-energy QCD predictions.

Contribution

It provides a detailed calculation of small-x resummation effects on gluon anomalous dimensions beyond NLO, including conformal contributions and their phenomenological implications.

Findings

Large negative corrections to the gluon splitting function at x < 0.01.

Importance of subleading terms in small-x resummation.

Quantitative effects on the s^omega behavior of cross sections.

Abstract

We discuss the quantitative consequences of the resummation of the small-x contributions to the anomalous dimensions beyond next-to-leading order in alpha_s and up to next order in ln(1/x) (NLx) in a framework based on the renormalization group equations. We find large and negative effects leading to negative values for the {\sf total} splitting function P_{gg}(x,alpha_s) already for x \lsim 0.01 at Q^2 \simeq 20 GeV^2. Terms less singular than those under consideration turn out to be quantitatively as important and need to be included. We derive the effects of the conformal part of the NLx contributions to the anomalous dimensions and discuss the exponent omega describing the s^omega behavior of inclusive cross sections.