Thermal modification of bottomonium spectra from QCD sum rules with the maximum entropy method

The bottomonium spectral functions at finite temperature are analyzed by employing QCD sum rules with the maximum entropy method. This approach enables us to extract the spectral functions without any phenomenological parametrization, and thus to visualize deformation of the spectral functions due to temperature effects estimated from quenched lattice QCD data. As a result, it is found that Upsilon and eta(b) survive in hot matter of temperature up to at least 2.3T(c) and 2.1T(c), respectively, while chi(b0) and chi(b1) will disappear at T < 2.5T(c). Furthermore, a detailed analysis of the vector channel shows that the spectral function in the region of the lowest peak at T = 0 contains contributions from the excited states, Upsilon(2S) and Upsilon(3S), as well as the ground states Upsilon(1S). Our results at finite T are consistent with the picture that the excited states of bottomonia dissociate at lower temperature than that of the ground state. Assuming this picture, we find that Upsilon(2S) and Upsilon(3S) disappear at T = 1.5-2.0T(c). (c) 2012 Elsevier B.V. All rights reserved.