High energy probes of the initial stages

• Kirill Boguslavki (Subatech, Nantes)

Room: Salle 135 **Abstract:** In the aftermath of heavy-ion collisions, the formation of the quark-gluon plasma is preceded by a short-lived, highly energetic, out-of-equilibrium state. This pre-equilibrium medium evolves through multiple stages on its way toward hydrodynamization, offering new opportunities for experimental exploration, especially with the upcoming high-luminosity heavy-ion program and medium-sized collision systems at the LHC. In this talk, I will discuss the potential of hard QCD probes, such as jets and heavy quarks, to provide a tomographic picture of the evolving medium and to infer unique non-equilibrium properties of many-body QCD. Produced at the earliest times, these probes strongly interact with the medium throughout its evolution and may be sensitive to distinct non-equilibrium features, including enhanced momentum broadening and momentum-space anisotropies, with direct consequences for jet quenching and heavy-quark diffusion.

Q&A and Discussion Room: Salle 135

Dileptons as probes of the pre-equilibrium stage in heavy and light-ion collisions

• Maurice Coquet (CERN)

Room: Salle 135 **Abstract:** Dileptons are among the golden probes of the deconfined medium produced in heavy-ion collisions. As they are emitted throughout the system’s evolution, they in particular encode direct information about pre-equilibrium dynamics. This talk focuses on phenomenology studies on the sensitivity of dilepton spectra to the timescale of equilibration, and to momentum-space anisotropies of the medium at early times, through the angular distribution of lepton pairs. In addition, recent measurements of jet quenching in OO collisions at the LHC further motivate the search for QGP dilepton production in light-ion systems, where, due to the shorter expected lifetime of the medium, the pre-equilibrium contribution may dominate over the thermal contribution in the intermediate mass range. We will thus discuss how dilepton measurements can help disentangle pre-equilibrium emission from Drell-Yan and later thermal production across system sizes, offering insight into the early stages of QCD matter.

Q&A and Discussion Room: Salle 135