Evidence for ${{\chi }_b}^{\prime }$ Production in the Exclusive Reaction ${\Upsilon }^{\prime \prime }\to \gamma {{\chi }_b}^{\prime }\to (\gamma \gamma {\Upsilon }^{\prime } or \gamma \gamma \Upsilon )$

Evidence is presented for the production of ${{\chi }_b}^{\prime }$ states ($2{}_{}{}^3{}_{}{}^{}P$) in the reaction ${\Upsilon }^{\prime \prime }\to \gamma {{\chi }_b}^{\prime }\to \gamma \gamma {\Upsilon }^{\prime } (or \gamma \gamma \Upsilon )$ with subsequent decay of the ${\Upsilon }^{\prime }\left(\Upsilon \right)$ into $e^{+}{e}^{-}$ or ${\mu }^{+}{\mu }^{-}$. The data were obtained with the nonmagnetic CUSB detector at the Cornell $e^{+}{e}^{-}$ storage ring. Observed were 14 (15) events consistent with the transition to the ${\Upsilon }^{\prime }\left(\Upsilon \right)$ with an estimated background of 1.7 (1.3) events. The lower-energy photons cluster around 100 MeV, implying $M\left({\Upsilon }^{\prime \prime }\right)-M\left({{\chi }_b}^{\prime }\right)\sim 100$ MeV. A single-line interpretation of the lower-energy photon spectrum is disfavored.