Dr. Raghav Kunnawalkam Elayavalli, Yale University

"Era of Jet-SubStructure and its utility in proton-proton and heavy-ion collisions"

Abstract: Jets, originating from hard scatterings of quarks/gluons (partons), have been established as an important probe of the Quark-Gluon Plasma (QGP), resulting in the discovery of parton energy loss or jet quenching. A common method of measuring the effects of jet quenching is by comparing properties of jets in proton-proton (pp) collisions as a vacuum/non-QGP baseline to their counterpart in heavy ion collisions. Any modifications to these observables can then point to the QGP transport properties which are inferred from theoretical/Monte-Carlo calculations. Since jet evolution intimately depends on both the momentum and angular scales, disentangling these scales via jet substructure (JSS) tools can lead to a more differential study of parton energy loss aimed at extracting the fundamental properties such as QGP coherence length or quantify soft gluon radiations. In essence, understanding the parton shower and JSS in vacuum is a necessary prerequisite for knowing how jets are quenched, which is in turn required for extracting the QGP's microscopic properties via jet-tomography. In this talk, I will start from a pedagogical overview of jet and JSS and present recent measurements from the STAR collaboration of JSS observables in p-p and Au-Au collisions at $sqrt{s_{NN}} = 200$ GeV. These measurements are aimed at describing the vacuum parton shower and utilize JSS tools to isolate a special selection of jets in heavy ion collisions who’s energy loss mechanism can then be studied in a differential fashion. I will conclude the talk by framing these measurements in the larger context and discuss how JSS can contribute towards novel studies of quantum entanglement and hadronization.