Using Jets as Probes to Study the Medium Response and the Quasiparticle Nature of the Quark Gluon Plasma

Jet observables are predicted to be sensitive to the short-length structure of the quark gluon plasma, or QGP, through Moilère-like scatterings off quasiparticles in the medium and the response of the medium to the jet. Models have shown that jet shapes and fragmentation functions are more sensitive to the contribution of the wake than quasiparticle scatterings. However, it has been also shown that we can identify various jet substructures that are insensitive to the wake contribution and that show reasonable sensitivity to scattering off quasiparticles, in particular for jets recoiling from colorless photons. Recently, data from the LHC has provided the first evidence of medium response as a result of jet-medium interactions, with the effect manifesting in a search for the depletion wake. This medium response has been long anticipated and widely incorporated into theoretical descriptions of jets in the QGP, but experimentally challenging to observe because of confounding signals such as medium-induced gluon radiation. In this talk, the lessons of the search for medium response will be applied to the search for signatures of the quasiparticle nature of the QGP. The difficulties of measuring characteristic quasiparticle behaviors, such as Moilère-like scatterings, will be identified and plausible candidate observables discussed.