RUI: Relativistic Heavy-Ion Theory

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Relativistic nuclear collision experiments explore interactions of quarks and gluons, the elementary particles that feel the strong nuclear force. Since the strong force is much stronger than the electromagnetic force, improving our understanding could drive the future frontiers of technology. The Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC) collide nuclei together at nearly the speed of light to create a hot and dense soup of quarks and gluons called quark-gluon plasma (QGP). Determining characteristic properties of QGP, like its viscosity or the time it takes to reach equilibrium, is an important way to constrain theories of the strong force. The leading theoretical calculations assume that the strong force rapidly drives the QGP toward equilibrium, but if this is not true in the experimental systems there will be a misinterpretation of the measured characteristic properties. This project focuses on theoretical methods for modeling the expansion and cooling of QGP, determining if QGP reaches an equilibrium state, and investigating how the interplay of expansion and equilibration will effect measurements. This project has strong emphasis on undergraduate education, and since most physics undergraduates will find careers outside of science, they will apply this education in uncountably many roles in society.Much interpretation that the medium produced in nuclear collisions is QGP results from the agreement of hydrodynamic models with experimental data. As experimental measurements improve, theories need to include deeper and more detailed physics. Moreover, hydrodynamic models use equations of state emerging from Quantum Chromodynamics calculations of locally equilibrated matter. If the medium is not actually in local equilibrium, then the properties that are inferred by hydrodynamics are not necessarily those of QGP. This project will address these issues by developing theoretical methods of hydrodynamics and kinetic theory to include stochastic effects from local and non-local noise and particle jets. Objectives include (1) deriving evolution equations for two-particle correlation observables that highlight the behaviors of partially equilibrated collision events, (2) investigating the influence of partial equilibration on small systems and Beam Energy Scan collision events at RHIC, (3) investigating how jet interactions could produce medium fluctuations and final state correlations that are distinguishable from those described by initial state or thermal sources, and (4) investigating new observables that distinguish the effects of different physical sources of correlations. This work will establish the first ever active physics research program at Lawrence Technological University and integrate this research activity into undergraduate education.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.