Speaker
Description
We study charmonium and bottomonium properties at nonzero temperature using lattice QCD covering temperatures in the range 153 MeV $<T<$ 305 MeV. We compute Euclidean correlation functions using both point meson operators, where the quark and antiquark fields are located at the same spatial point, and extended meson operators, where the quark and antiquark fields are spatially separated to enhance overlap with physical quarkonium states.
We show for the first time that the masses and widths obtained from point and extended meson operators are consistent with each other, providing an important cross-check for the spectral analysis. We find that the in-medium quarkonium masses show no significant temperature dependence within uncertainties, in contrast to common expectations based on color screening. On the other hand, the thermal widths clearly increase with temperature, indicating substantial in-medium broadening of quarkonium states.