Cone-Dependent Jet Collisional Energy Loss in Finite QCD Medium

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 $R!\to!π$, 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.

💡 Research Summary

In this work the authors develop a first‑principles, HTL‑resummed calculation of the collisional (elastic) energy loss of a reconstructed jet propagating through a finite‑size, finite‑temperature QCD medium, explicitly accounting for the jet cone radius R. Starting from the one‑loop diagram with a single HTL‑screened gluon exchange between an energetic parton and a thermal medium constituent, they introduce a finite‑size factor 1 – exp