Cone-dependent jet collisional energy loss in finite QCD medium

We derive a compact HTL-resummed expression for the leading-order cone-restricted collisional energy loss associated with a jet-initiating parton in a finite-size, finite-temperature QCD medium. Using a cone-selection parameter R to define the energy retained inside a parton-level cone, we obtain the out-of-cone elastic energy transfer with an explicit separation between contributions from the primary parton and recoiling medium partons. The result reproduces the known partonic limit as R → 0, vanishes for R → π , and applies to both light- and heavy-flavor jet-initiating partons. Numerically, the elastic component shows a distinct non-linear R dependence, and its relative importance increases with R , becoming comparable to or exceeding the radiative contribution for sufficiently large cone sizes. The path-length dependence remains close to linear for all R , while the medium-response contribution can exceed 10% for realistic cone sizes.