A comparison of spectral reconstruction methods applied to non-zero temperature NRQCD meson correlation functions

Abstract

We present results from the fastsum collaboration's programme to determine the spectrum of the bottomonium system as a function of temperature. Three different methods of extracting spectral information are discussed: a Maximum Likelihood approach using a Gaussian spectral function for the ground state, the Backus Gilbert method, and the Kernel Ridge Regression machine learning procedure. We employ the fastsum anisotropic lattices with 2+1 dynamical quark flavours, with temperatures ranging from 47 to 375 MeV.

Heavy quarks at finite temperature

“…So far, a clear picture has not emerged yet; applied to the same correlators, the mass shifts may be positive or negative, and the widths do not reveal a pattern consistent between the various methods, as indicated in Fig. 3; preliminary results were discussed at this conference [53][54][55] and summarized in further conference proceedings [56].…”

“…The HotQCD results [50][51][52]59] using extended sources generally support the strong-binding scenario. Older results from FASTSUM [48] or HotQCD [49] as well as preliminary FASTSUM results [53][54][55][56]60] with local point sources paint a less conclusive picture. Thermal Wilson loops or Coulomb gauge Wilson line correlators have been analyzed by the HotQCD collaboration [58].…”