Towards a Yoctosecond Imaging Tool of the Quark-Gluon Plasma

Abstract:

The quark-gluon plasma (QGP) is a hot and dense QCD state of matter where quarks and gluons are not confined inside hadrons. It is produced in the aftermath of ultrarelativistic heavy ion collisions (HICs) at the Relativistic Heavy Ion Collider and the Large Hadron Collider. To experimentally extract the properties of QGP one often uses jets, collimated sprays of hadrons which result from the fragmentation of highly energetic quarks and gluons.

Jets are abundantly produced in collider experiments and, in HICs, they are produced concurrently with the QGP, through which they have to propagate at multiple stages of their evolution. In recent years,, the modifications of the overall energy and of the internal structure of in-medium jets with respect to the proton-proton baseline, i.e., without QGP production, have been identified as a promising path to perform time-differential measurements of QGP evolution.

In this presentation, I will discuss the steps we are taking in the direction of solidifying jets as a QGP time-imaging tool. In particular, I will present a recently introduced observable which aims at quantifying jet energy loss while suppressing an important migration bias that is inevitable if jet comparison is made at the same reconstructed transverse momentum of the jet.

In doing so, one has an unbiased estimate of the balance between out of cone medium-induced radiation and QGP response correlated with the jet which falls inside the jet cone. Furthermore, I will present a calculation of the spin-dependent production of a quark-antiquark pair from an initial unpolarized gluon in an anisotropic QGP medium. By studying how the angular and spin dependence of this production spectrum couples to medium anisotropies, one can gain insight on the early, out-of-equilibrium dynamics of QGP evolution.