Speaker
Description
Quarks and gluons within a proton are confined within a volume in which the energy density and pressure are comparable to those of quark-gluon plasma (QGP) at or just above the QCD transition temperature. With this as motivation, I will investigate the interplay between the thermodynamic (Gibbs) entropy of QGP and the entanglement entropy of confined hadronic states across the quark-hadron phase transition. Upon hadronization, the Gibbs entropy of the droplet of QGP that becomes a proton must be reorganized into the entanglement entropy of quantum correlations with said proton. This entanglement entropy is a repository for the converted thermodynamic entropy. Three different arguments, each qualitative but with quite different sources of uncertainty, yield estimates of the magnitude of the entanglement entry carried by a proton that are similar in magnitude to the Gibbs entropy of the QGP from which a proton forms at the phase boundary. This provides a new lends on the microscopic mechanism of confinement and the nature of the QCD phase transition. A principal lesson from recreating droplets of such QGP in heavy ion collisions is that it is a strongly coupled liquid, not a plasma of partons. Given this, a central question for the future Electron-Ion Collider (EIC) will be the investigation of correlations between nearby partons within a proton. I will present an observable involving measurements of a jet and a pion as well as the scattered electron via which EIC measurements can seek and quantify the existence of short-range correlations (SRCs) between $ud$ quark pairs within a proton and differentiate a strongly coupled interior of a proton from a picture in which the proton can be understood one parton at a time via (generalized) parton distribution functions.