Heavy quarkonium in a weakly-coupled quark-gluon plasma below the melting temperature

We calculate the heavy quarkonium energy levels and decay widths in a quark-gluon plasma, whose temperature T and screening mass m D satisfy the hierarchy mα s ≫ T ≫ mα s 2 ≫m D (m being the heavy-quark mass), at order mα s 5 . We first sequentially integrate out the scales m, mα s and T, and, next, we carry out the calculations in the resulting effective theory using techniques of integration by regions. A collinear region is identified, which contributes at this order. We also discuss the implications of our results concerning heavy quarkonium suppression in heavy ion collisions