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Comments on parton saturation at small x in large nuclei

M. A. Braun

TL;DR

The paper analyzes two notions of gluon density in the small-x regime for large nuclei: the standard density defined through DIS structure functions and Mueller's density tied to a gluonic current. It demonstrates that Mueller's density is a distinct quantity from the standard one but exhibits the same saturation behavior, while a soliton-density approach shows the standard density can undergo supersaturation, whereas Mueller's density saturates at small momenta. The analysis extends to quark densities, revealing that the corresponding xq_M inherits similar saturation properties. The discussion highlights interpretational issues and suggests Mueller-style densities may not universally describe parton distributions, leaving the question of the 'correct' density open.

Abstract

It is argued that the gluon density introduced by A.Mueller in relation to the saturation phenomenon is different from the standardly defined one, which turned out to have a soliton-like form in the numerical calculations. It is shown that A.Mueller's densities obtained from the latter possess the same saturation properties as originally predicted.

Comments on parton saturation at small x in large nuclei

TL;DR

The paper analyzes two notions of gluon density in the small-x regime for large nuclei: the standard density defined through DIS structure functions and Mueller's density tied to a gluonic current. It demonstrates that Mueller's density is a distinct quantity from the standard one but exhibits the same saturation behavior, while a soliton-density approach shows the standard density can undergo supersaturation, whereas Mueller's density saturates at small momenta. The analysis extends to quark densities, revealing that the corresponding xq_M inherits similar saturation properties. The discussion highlights interpretational issues and suggests Mueller-style densities may not universally describe parton distributions, leaving the question of the 'correct' density open.

Abstract

It is argued that the gluon density introduced by A.Mueller in relation to the saturation phenomenon is different from the standardly defined one, which turned out to have a soliton-like form in the numerical calculations. It is shown that A.Mueller's densities obtained from the latter possess the same saturation properties as originally predicted.

Paper Structure

This paper contains 6 sections, 35 equations, 1 figure.

Table of Contents

  1. Introduction
  2. Gluonic distributions: standard and of A.Mueller
  3. The soliton density and saturation
  4. The quark density from the soliton gluonic density
  5. Discussion
  6. References

Figures (1)

  • Figure 1: Interaction of a probe with the target. Thick lines show partons (gluons or quarks) directly coupled to the probe. Thin lines show exchanged gluons.