Sensitivity of some Jet Observables to the Presence of Quasiparticles in QGP

by Krishna Rajagopal

Thursday 11 Aug 2022, 15:00 → 16:00 Europe/Zurich

4/3-006 - TH Conference Room (CERN)

QGP, a strongly coupled liquid when viewed at length scales of O(1/T), must reveal quark- and gluon-like quasi-particles when probed with sufficiently high momentum transfer, since QCD is asymptotically free. High energy jet partons traversing the droplet of QGP produced in a heavy ion collision can trigger these high-momentum exchanges with medium constituents and so have the potential to reveal the presence of such quasi-particles, a key step toward the experimental study of the microscopic structure of QGP.  We implement this physics within the hybrid strong/weak coupling model which, prior to this work, only accounted for nonperturbative aspects of parton energy loss. Elastic Moliere scatterings between partons from a jet shower and medium  quasi-particles results in deflection of the propagating jet partons and struck thermal medium partons recoiling at large angles. All these partons lose energy, creating wakes from energy and momentum injected into the QGP fluid.  We discuss the effect of Moliere scatterings on some widely used groomed and ungroomed jet substructure observables. Given the large impact on jet observables of the wakes generated by the hydrodynamic response of the QGP fluid as the shower and scattered partons lose energy and momentum to it, as well as the presence of selection biases, finding distinctive signatures of Moliere scattering, and hence the presence of quasi-particles in QGP, is a challenge. Toward this end, we emphasize the discovery potential of subjet (jets within jets) distributions.