Cone-Dependent Jet Collisional Energy Loss in Finite QCD Medium

TL;DR

This paper derives a compact expression for jet collisional energy loss in a finite QCD medium, revealing a significant non-linear dependence on jet cone size and highlighting the importance of elastic energy loss for larger jet radii.

Contribution

It provides a new HTL-resummed formula for out-of-cone elastic energy loss, explicitly separating jet and medium contributions, applicable to both light and heavy jets.

Findings

Elastic energy loss increases with jet radius R.

Elastic component can surpass radiative loss at large R.

Path-length dependence remains nearly linear across R.

Abstract

We derive a compact HTL-resummed expression for the leading-order jet collisional energy loss in a finite-size, finite-temperature QCD medium. Defining the jet energy inside a cone of radius $R$, we obtain the out-of-cone elastic energy loss with an explicit separation between contributions from the primary jet parton and recoiling medium partons. The result reproduces the known partonic limit as $R\!\to\!0$, vanishes for $R\!\to\!\pi$, and applies to both light- and heavy-flavor jets. Numerically, the elastic component shows a pronounced non-linear $R$ dependence relative to the radiative baseline, and its importance increases with $R$, becoming comparable to or exceeding the radiative contribution for sufficiently large jet radii. The path-length dependence remains close to linear for all $R$, while the medium-response contribution can exceed $10\%$ for realistic jet radii.