Observation of P-wave bb-bar bound states

The existence of $P$-wave $b\overline{b}$ bound states ${{\ensuremath{\chi}}_{b}}^{\ensuremath{'}}$ is demonstrated by observation of photons from the transition ${\ensuremath{\Upsilon}}^{\ensuremath{'}\ensuremath{'}}\ensuremath{\rightarrow}\ensuremath{\gamma}+{{\ensuremath{\chi}}_{b}}^{\ensuremath{'}}$ in the inclusive photon spectrum from ${\ensuremath{\Upsilon}}^{\ensuremath{'}\ensuremath{'}}$ decays. The center of gravity of the observed photon energies is 98 MeV and the branching ratio for the transition of the ${\ensuremath{\Upsilon}}^{\ensuremath{'}\ensuremath{'}}$ to the ${{\ensuremath{\chi}}_{b}}^{\ensuremath{'}}$ states is (34\ifmmode\pm\else\textpm\fi{}3)% (statistical).