Relativistic corrections in quarkonium

Abstract

Relativistic corrections to quarkonium energy levels and electric dipole transition rates are calculated. We find a consistent description with both electric confinement and tensor quark-antiquark forces at distances beyond that at which perturbative QCD should be valid. The preliminary masses of the ${\chi }_b$ and ${\chi }_b^{\prime }$ levels are described satisfactorily. The transitions ${\Upsilon }^{\prime \prime }\to \gamma {\chi }_b$, suppressed in some nonrelativistic models, are predicted to be observable here.