Understanding parton evolution in matter from renormalization group analysis

TL;DR

This paper develops a renormalization group framework for analyzing parton evolution in nuclear matter, providing a new approach to resummation of medium-induced radiation effects in deep inelastic scattering.

Contribution

It introduces a novel RG evolution equation for parton fragmentation in matter, differing from traditional methods in regulating collinear divergences and enabling efficient phenomenological analysis.

Findings

Derived RG equations resum multiple emissions near splitting function endpoints.

Applied the framework to study fragmentation in electron-nucleus reactions.

Offers analytic insights and improved efficiency for phenomenological modeling.

Abstract

We perform a renormalization group (RG) analysis of collinear hadron production in deep inelastic scattering on nuclei. We consider the limit where the parent parton energy $E$ is large, while the medium opacity $L/\lambda_g$ remains small. We identify the fixed order and leading $\ln(E/\xi^2 L)$ enhanced medium contributions to the semi-inclusive cross sections and derive RG equations that resum multiple emissions near the endpoints of the splitting functions at first order in opacity. These evolution equations treat the same type of radiation enhancement in matter as the modified Dokshitzer-Gribov-Lipatov-Altarelli-Parisi approach, but differ in the way one regulates the collinear divergences. They provide a unique analytic insight into the problem of resummation and a faster and more efficient path to phenomenology. The new RG evolution framework is applied to study fragmentation in $e$A reactions.