Heavy Quarkonia as Thermometer of Quark-Gluon Plasma

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The strong force is one of the fundamental forces in nature, described by a quantum field theory called Quantum Chromodynamics (QCD). This force is responsible for binding elementary particles, called quarks, into protons and neutrons, and the latter into atomic nuclei. Under normal conditions in our everyday world quarks are always bound into composite objects and isolated quarks are never observed. However, when strongly interacting matter is heated to extreme temperatures (a million times the temperature in the core of the sun and above) a novel phase of matter, called a Quark-Gluon Plasma (QGP), appears where composite objects melt and quarks become the deconfined fundamental degrees of freedom. The PI will perform a first-principle study of how composite states of heavy quarks, referred to as heavy quarkonia, behave in a QGP. Theoretical knowledge of their properties and melting patterns provides information about QGP and allows us to study the microscopy of QGP, the nature of quark confinement and the strong force in general. The investigations in this project are of great relevance for explaining the findings of the experimental program of relativistic heavy-ion collisions, performed at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory and the Large Hadron Collider at the European Organization for Nuclear Research.This project seeks to carry out first-principle, parameter-free predictions of heavy quarkonia spectral functions that encode all information about the quarkonia states, from the fundamental QCD Lagrangian. The PI will develop novel theoretical and computational methods for performing Monte Carlo lattice gauge theory computations with anisotropic Highly Improved Staggered Quarks (aHISQ) action. The heavy quarks will be included in the framework of Non-Relativistic QCD (NRQCD). The PI will also develop Bayesian inference techniques for solving the inverse problem that arises when reconstructing the spectral functions from the lattice QCD data. These new methods will be explored, tested with the available lattice data, and implemented in an open-source codebase. The main goal is to achieve predictive results on the spectral functions with fully assessed statistical and systematic uncertainties. The PI will mentor doctorate students involved in the research as well as engage in public outreach activities.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.