Small x resummation in collinear factorisation

TL;DR

This paper revisits small x resummation in collinear factorisation, deriving a new K-factor in leading ln x approximation, and demonstrates its impact on structure functions and vector meson production.

Contribution

It presents a revised derivation of the K-factor for small x resummation, differing from previous work, and extends the formulation to channels with non-zero conformal spin.

Findings

New K-factor expression differs from previous results.

Demonstrated impact on structure function F_L.

Applied to exclusive vector meson electroproduction.

Abstract

The summation of the small x-corrections to hard-scattering QCD amplitudes by collinear factorisation method is reconsidered and the K-factor is derived in leading ln x approximation with a result differing from the corresponding expression by Catani and Hautmann (Nucl. Phys. B 427, 475, 1994). The significance of the difference is demonstrated in the examples of structure function F_L and of exclusive vector meson electroproduction. The formulation covers the channels of non-vanishing conformal spin n paving the way for new applications.