# Parton Energy Loss and the Generalized Jet Transport Coefficient

## TL;DR

This paper revisits radiative parton energy loss in deep inelastic scattering, deriving a generalized jet transport coefficient through a detailed QCD calculation that extends previous models and compares different approximations.

## Contribution

It introduces a new formulation of the gluon radiation spectrum in DIS using unintegrated quark-gluon correlations and defines a generalized TMD jet transport coefficient.

## Key findings

- Derived the gluon radiation spectrum without collinear approximation.
- Expressed the spectrum in terms of TMD quark-gluon correlations.
- Numerically compared results under different approximations.

## Abstract

We revisit radiative parton energy loss in deeply inelastic scattering (DIS) off a large nucleus within the perturbative QCD approach. We calculate the gluon radiation spectra induced by double parton scattering in DIS without collinear expansion in the transverse momentum of initial gluons as in the original high-twist approach. The final radiative gluon spectrum can be expressed in terms of the convolution of hard partonic parts and unintegrated or transverse momentum dependent (TMD) quark-gluon correlations. The TMD quark-gluon correlation can be factorized approximately as a product of initial quark distribution and TMD gluon distribution which can be used to define the generalized or TMD jet transport coefficient. Under the static scattering center and soft radiative gluon approximation, we recover the result by Gylassy-Levai-Vitev (GLV) in the first order of the opacity expansion. The difference as a result of the soft radiative gluon approximation is investigated numerically under the static scattering center approximation.