Kei Suzuki, Philipp Gubler, Kenji Morita, Makoto Oka
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. As a result, it is found that \Upsilon and \eta_b survive in quark-gluon matter of temperature up to 2.5 -3.0T_c, while \chi_{b0} and \chi_{b1} will dissociate at 2.0 -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, our results suggest that \Upsilon(2S) and \Upsilon(3S) disappear at T=1.5 -2.0T_c.
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http://arxiv.org/abs/1204.1173
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