Medium-induced gluon radiation in hard forward parton scattering in the saturation formalism

TL;DR

This paper derives the spectrum of medium-induced gluon radiation during forward parton scattering in nuclei using the saturation formalism, connecting it with previous opacity expansion results and aiding in modeling nuclear suppression effects.

Contribution

It provides a rigorous derivation of the gluon radiation spectrum within the saturation formalism, clarifying its validity and relation to opacity expansion approaches.

Findings

Reproduces the known spectrum expression in saturation formalism

Establishes the validity range of the spectrum calculation

Connects saturation and opacity expansion formalisms

Abstract

We derive the medium-induced, coherent gluon radiation spectrum associated with the hard forward scattering of an energetic parton off a nucleus, in the saturation formalism and within the Gaussian approximation for the relevant correlators of Wilson lines. The calculation reproduces the simple expression for the spectrum previously obtained in the opacity expansion formalism, and rigorously specifies its validity range. The connection between the calculations in the opacity expansion and saturation formalisms is made apparent. This study may serve as a first step in order to implement consistently induced coherent energy loss and gluon shadowing in `saturation-based models' of hadron nuclear suppression in proton-nucleus collisions.