Thursday, October 29, 2026
4:00 pm-5:00 pm
From Confinement to Deconfinement: Probing QCD with Jets and Their Substructure
Quarks and gluons, the fundamental constituents of visible matter, are governed by Quantum Chromodynamics (QCD) — a theory rich in phenomena spanning vastly different energy scales. At low energies, confinement binds quarks and gluons into hadrons (protons, neutrons, and other composite particles); at extreme temperatures and densities, these constituents escape their confines and form a new phase of matter: the quark-gluon plasma (QGP). Understanding how the interactions of quarks and gluons lead to the formation and disintegration of hadrons, along with a study of the properties of nuclei and the QGP, are fundamental goals of nuclear physics.
Jets, the collimated sprays of hadrons produced in high-energy collisions, serve as powerful probes of QCD across both regimes. In this talk, I will focus on jet substructure, the internal structure of jets, and in particular a class of observables known as energy correlators, which measure energy-weighted angular correlations between particles within a jet. In proton-proton collisions at the LHC, two- and three-point energy correlator (EEC, E3C) measurements reveal a clear transition from perturbative to non-perturbative QCD processes associated with confinement, and their ratio provides direct sensitivity to the strong coupling constant. I will also discuss EEC measurements in heavy-flavor quark-initiated jets, which probe the mass dependence of the quark and gluon fragmentation cascade and hadronization. Extending these studies to heavy-ion collisions, I will present EEC measurements in Pb-Pb collisions, which offer novel probes of QGP properties and jet-medium interactions.
