B-Meson Gateways to Missing Charmonium Levels

We outline a coherent strategy for exploring the four remaining narrow charmonium states [${\eta }_c^{\mathrm{\prime }}(2\text{slj}110)$, $h_c(1\text{slj}121)$, ${\eta }_{c2}(1\text{slj}132)$, and ${\psi }_2(1\text{slj}332)$] expected to lie below charm threshold. Produced in $B$-meson decays, these levels should be identifiable $\mathit{\text{now}}$ via striking radiative transitions among charmonium levels and in exclusive final states of kaons and pions. Their production and decay rates will provide much needed new tests for theoretical descriptions of heavy quarkonia.