Bottomonium above Deconfinement in Lattice Nonrelativistic QCD

Abstract

We study the temperature dependence of bottomonium for temperatures in the range 0.4Tc < T < 2.1Tc, using nonrelativistic dynamics for the bottom quark and full relativistic lattice QCD simulations for N f = 2 light flavors on a highly anisotropic lattice. We find that the Υ is insensitive to the temperature in this range, while the χ b propagators show a crossover from the exponential decay characterizing the hadronic phase to a power-law behaviour consistent with nearly-free dynamics at T ≃ 2Tc.

Melting of P wave bottomonium states in the quark-gluon plasma from lattice NRQCD

“…This is indeed the case at the lowest temperature and leads to the zero-temperature spectrum discussed in Refs. [13,14]. Above T c , we observe that the effective masses no longer follow the trend given by the correlator below T c , but instead bend away from the lowtemperature data.…”

“…are not present [13]. Moreover, the entire euclidean time interval can be used, due to the absence of backward moving states.…”

“…In Ref. [13] first results for P waves were presented (in the χ b channels). In the QGP phase we observed clear indications for nonexponential decay of the euclidean lattice correlators, which was interpreted as the melting of the ground (and excited) states.…”

“…In Ref. [13] we studied correlators (and no spectral functions) at only four temperatures with limited statistics: here we extend this to the full ensemble also used in Refs. [14,15] and provide the spectral functions, obtained with the help of the Maximum Entropy Method (MEM).…”

“…In a series of papers [13][14][15] we have studied bottomonium at nonzero temperature using simulations of lattice QCD, in which the heavy b quarks propagate nonrelativistically through a quark-gluon plasma with N f = 2 flavours. We use a highly anisotropic lattice formulation, with a total of seven different temperatures up to 2.1T c .…”