Medium Characterization with Hard Probes: From Cherenkov Light in QED to Jet Drift in QCD

TL;DR

This dissertation introduces a unified approach to medium characterization using hard probes, covering Cherenkov light in QED and jet drift in QCD, with applications in particle identification and quark-gluon plasma tomography.

Contribution

It develops a dispersive fit for liquid argon refractive index and employs jet drift simulations to analyze medium effects in high-energy nuclear collisions.

Findings

Cherenkov angular distribution is sensitive to refractive index peaks.

Jet drift shows distinct systematics in flow and acoplanarity observables.

Abstract

This dissertation presents a unified framework for medium characterization with hard probes spanning from Cherenkov light in quantum electrodynamics (QED) to jet drift in quantum chromodynamics (QCD). We first develop a dispersive fit to the refractive index $n(\lambda)$ of liquid argon (LAr) by incorporating anomalous dispersion at the 106.6 nm resonance for the first time. We show that the angular distribution of Cherenkov radiation is highly sensitive to the peak of the refractive index and contributes a significant excess over isotropic scintillation in certain angular bins. This work is important for precision Particle Identification (PID) for experiments like DUNE and CCM. Transitioning to high-energy nuclear collisions, we utilize ``jet drift'' -- the flow-induced deflection of partons -- as a tomographic probe of the Quark-Gluon Plasma (QGP). Using the Anisotropic Parton Evolution (APE) Monte Carlo simulation across various collision systems (PbPb, AuAu, and UU), we disentangle how the jet modification depends on medium size, temperature, and geometry. We show that jet drift exhibits distinct systematics in observables like the elliptic flow ($v_2$) and dihadron acoplanarity ($\Delta\phi$), which helps disentangle it from conventional energy loss. Together, these studies demonstrate how the angular and kinematic signatures of hard probes revolutionize our ability to resolve the fundamental properties of matter.