Jet evolution in vacuum and in medium: a unified approach

Jets are collimated bursts of energetic hadrons produced in high-energy collisions, which serve as tools for testing quantum chromodynamics, the theory of strong interactions. The observed suppression of jet spectra in heavy-ion collisions, compared to proton-proton collisions, implies the existence of a dense medium called quark-gluon plasma (QGP). Energy loss is caused by jet constituents traversing the QGP. The Baier-Dokshitzer-Mueller-Peigné-Schiff (BDMPS) formalism can be used to calculate the nuclear modification factor (RAA), the magnitude of jet quenching, but is limited to describing radiative loss of a single parton. In this work, we unify the BDMPS formalism with two additional phenomena: color decoherence – the medium's ability to resolve two spatially-separated color charges – and vacuum energy loss, governed by the nonlinear Banfi-Marchesini-Smye (BMS) equation. Numerically solving the BMS equation with new initial conditions, we find that the RAA exhibits a strong sensitivity to the decoherence angle. Specifically, decoherence effects can further reduce the RAA by 10-50%. We also find a new universal scaling governed by the decoherence angle. These results offer a promising new basis for jet quenching phenomenology.