Imaging non-hydrodynamic modes with jet wakes
arXiv:2607.26851
The authors propose that the angular pattern of the energy deposited by a jet (the jet wake) in heavy‑ion collisions can be used to detect non‑hydrodynamic excitations of the quark‑gluon plasma, with higher angular moments directly encoding these microscopic modes.
Abstract
While studies of ultra-relativistic heavy-ion collisions have established that the quark--gluon plasma exhibits hydrodynamic behavior, direct signatures of non-hydrodynamic modes have remained elusive, and no observable is known to be exclusively sensitive to them. Here, we show that the angular structure of the jet wake provides such a probe. In the long-wavelength limit, hydrodynamics contributes only to the lowest angular moments of the detector image of the jet wake, while higher moments directly encode microscopic non-equilibrium dynamics. The jet wake thus serves as a spectroscopic probe of the medium's non-hydrodynamic sector. We develop a general kinetic-theory framework relating the angular moments of the late-time energy flux generated by a jet to the relaxation spectrum of the collision operator. In all models considered, non-hydrodynamic modes leave distinct imprints on the higher angular moments. Our results motivate precision measurements of the higher angular moments of the negative jet wake.
5 pages + appendix, 3 figures