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 m alpha(s) >> T >> m alpha(2)(s) >> m(D)(m being the heavy-quark mass), at order m alpha(5)(s). We first sequentially integrate out the scales m, mas 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.