Spin-orbit inversion of excited heavy quark mesons

The mesonic heavy quark spin multiplets with $s_{\mathcal{l}}^{{\pi }_{\mathcal{l}}}={\frac{1}{2}}^{+}$ and ${\frac{3}{2}}^{+}$ are expected to be the lowest-lying excitations above the pseudoscalar and vector ground states with $s_{\mathcal{l}}^{{\pi }_{\mathcal{l}}}={\frac{1}{2}}^{-}.$ I show that for charm and bottom these multiplets are probably inverted, with the $2^{+}$ and $1^{+}$ states with $s_{\mathcal{l}}^{{\pi }_{\mathcal{l}}}={\frac{3}{2}}^{+}$ about 150 MeV below the $1^{+}$ and $0^{+}$ states with $s_{\mathcal{l}}^{{\pi }_{\mathcal{l}}}={\frac{1}{2}}^{+}.$ If verified, such an inversion would both support the expectation that confinement has no dynamical spin-dependence and indicate that heavy- and light-quark systems may be characterized by the same effective low-energy degrees of freedom. As an important by-product, this work establishes the dynamics of the strange quark as a critical link between heavy- and light-quark hadrons, justifying efforts toward a much more complete experimental and theoretical understanding of strange mesons and baryons and of strange quarkonia.