Quarkonium spectroscopy and perturbative QCD: a new perspective

We study the energy spectrum of bottomonium in perturbative QCD, taking alp ha (s) (M-Z) = 0.1181 +/- 0.0020 as input and fixing m(b)((MS) over bar) (m (b)((MS) over bar)) on the Y(1S) mass. Contrary to wide beliefs, perturbati ve QCD reproduces reasonably well the gross structure of the spectrum as lo ng as the coupling constant remains smaller than one. We perform a detailed analysis and discuss the size of nonperturbative effects. A new qualitativ e picture on the structure of the bottomonium spectrum is provided. The low est-lying c (c) over bar and b (c) over bar states are also examined. (C) 2 001 Published by Elsevier Science B.V.