Average kinetic energy of heavy quark and virial theorem

We derive the virial theorem of the relativistic two-body system for the study of B-meson physics. It is also shown that the solution of the variational equation always satisfies the virial theorem. From the virial theorem we also obtained μπ2 ≡ −λ1 ≡ 〈p2〉 = 0.40 ∼ 0.58 GeV2, which is consistent with the result of the QCD sum rule calculations of Ball et al.