Heavy Quarkonia in Lattice QCD with Anisotropic Highly Improved Staggered Quarks

Michigan State University, East Lansing MI

Investigators

Abstract

The strong force binds elementary particles called quarks into protons and neutrons and the latter into atomic nuclei that are the fundamental building blocks of the matter observed in the Universe at all scales. These strong interactions of the elementary constituents are successfully described by Quantum Chromodynamics (QCD) - a quantum field theory developed in the course of 20th century. Predictions of QCD have been verified with amazing experimental precision. Under normal conditions isolated quarks are not observed - they are confined in composite objects like protons and neutrons. However, when strongly interacting matter is heated up to very high temperatures (about million times the temperature in the core of the Sun) or compressed to very high densities (the ones presumably achieved at the core of a neutron star), a novel phase of matter called Quark-Gluon Plasma (QGP) is formed. This project will study from first-principle QCD calculations the properties of QGP, in particular, how composite states of heavy quarks respond to the QGP medium and how the strong force behaves at very short distance scales (microscopy of QGP). These investigations will provide theoretical understanding and interpretation of the experimental results from the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory and Large Hadron Collider at the European Organization for Nuclear Research. Lattice QCD simulations are performed by Monte Carlo sampling the most probable configurations of fundamental fields on the four-dimensional space-time grid and computing physical observables on them. The physical information about heavy-quark bound states is encoded in their spectral functions. For reliable extraction of the spectral functions from Euclidean lattice correlation functions, the PI will develop a formalism of anisotropic Highly Improved Staggered Quarks (aHISQ), where the space-time grid is anisotropic with higher resolution in the temporal direction. The project will develop necessary algorithms and computer codes for lattice QCD simulations with dynamical aHISQ quarks and will generate a publicly available library of high-quality aHISQ ensembles of field configurations at various lattice spacings and anisotropies specifically for heavy quarkonia spectral function reconstruction. The heavy quarks will be included in the framework of Non-Relativistic QCD (NRQCD). Very high anisotropies combined with dynamical aHISQ quarks will pave the way to reliable extraction of 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.