Non-relativistic QCD Study of Excited Bottomonia at Finite Temperatures on a Fine Lattice

TL;DR

This study uses lattice NRQCD to analyze how excited bottomonium states behave at finite temperatures, revealing thermal widths increase with temperature but masses remain stable.

Contribution

It provides the first detailed lattice NRQCD analysis of excited bottomonium states at finite temperatures with optimized operators and spectral function modeling.

Findings

Thermal widths of bottomonia increase with temperature.

Masses of bottomonia show negligible shifts at finite temperature.

In-medium properties are insensitive to operator variations.

Abstract

The temperature dependence of bottomonium correlators up to the 3S and 3P excited states are presented in the range $T \simeq 133-250$ MeV. These lattice calculations employ the non-relativistic QCD (NRQCD) approach for bottom quarks on (2+1)-flavor gauge backgrounds, using the highly improved staggered quark (HISQ) action near the physical point. The study utilizes a fine lattice spacing of 0.0493 fm at all temperatures. Extended bottomonium operators are implemented to achieve optimized overlaps with the targeted excited states, enhancing sensitivity to thermal effects. To probe in-medium modifications of excited bottomonia, we extract thermal widths and in-medium masses from bottomonium correlators, parameterizing the spectral function with a Gaussian ansatz. Our results confirm nonzero thermal widths for various bottomonium states as the temperature increases, while no significant mass shifts are observed. Additionally, we check that the in-medium properties of bottomonia are almost not affected by variations in the choice of extended operators.