Quarkonium in-medium properties from realistic lattice NRQCD

TL;DR

This study uses advanced lattice QCD simulations and Bayesian spectral reconstruction to analyze how bottomonium and charmonium states change in hot QCD matter near the crossover transition, providing robust insights into their in-medium properties.

Contribution

It offers the first comprehensive, uncertainty-aware analysis of quarkonium spectral functions at finite temperature using realistic lattice QCD and novel Bayesian methods.

Findings

Sequential in-medium modification of quarkonium states.

Quantitative reduction of heavy quarkonium masses with temperature.

Clarification of discrepancies in previous melting temperature reports.

Abstract

We present the final results of our high statistics study on the properties of bottomonium and charmonium at finite temperature. We focus on the temperature range around the crossover transition $150\leq T\leq 410$MeV, relevant for current heavy ion collision experiments. The QCD medium degrees of freedom which consist of dynamical u,d, and s quarks and gluons are captured by realistic state-of-the art ($m_\pi\approx 161$MeV) lattice QCD simulations of the HotQCD collaboration. For the heavy quarks we deploy the non-relativistic effective field theory of QCD, NRQCD. The in-medium properties of quarkonium are deduced from their spectral functions, which are reconstructed using improved and novel Bayesian approaches. Through a systematic analysis we shed light on the origin of the discrepancies in melting temperatures previously reported in the literature, showing that they are owed to underestimated methods uncertainties of the deployed spectral reconstructions. Our simulations corroborate a picture of sequential in-medium modification, ordered according to the vacuum binding energy of the states. As a central quantitative result, our study reveals how the mass of the heavy quarkonium ground state reduces as temperature increases. The observed spectral modifications are interpreted in the light of, and compared to previous studies based on the complex lattice potential for heavy quarkonium. Thus for the first time we provide a robust picture of in-medium heavy quarkonium modification in the quark-gluon plasma consistent among different non-relativistic methods. We also critically discuss the perspectives for improving on these results.