The gluon field of a fast moving nucleus and the effective langrangian for QCD at high energy

TL;DR

This paper derives the gluon field of a fast-moving nucleus using an effective QCD Lagrangian, comparing results with previous approaches and emphasizing gauge invariance.

Contribution

It introduces a gauge-invariant effective gluon field framework for high-energy QCD and compares perturbative potential calculations with prior methods.

Findings

Differences in results appear at order g^3 due to the gauge invariance of the gluon field.

The effective gluon field used is gauge invariant, contrasting with previous approaches.

The paper discusses the phenomenological implications of the different methods.

Abstract

Starting from the effective lagrangian for QCD at high energy we calculate the lowest perturbative contributions to the potential of a relativistic nucleus and compare our results to those derived by Kovchegov (see Y.V. Kovchegov, Phys. Rev. {\bf D55}, 5445 (1997)). The results differ already at order g^3 which can be traced to the fact that the meaning of the underlying gluon fields is different. (The effective gluon field we use is a gauge invariant object.) Both approaches should therefore be seen as alternatives, the relative merits of which have to be judged by their phenomenological success.