New measurements of Y(1S) decays to charmonium final states

Using data collected by the CLEO III detector at CESR, we report on measurements of $\ensuremath{\Upsilon}(1S)$ decays to charmonium final states. The data sample used for this analysis consists of $21.2\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $\ensuremath{\Upsilon}(1S)$ decays, representing about 35 times more data than previous CLEO $\ensuremath{\Upsilon}(1S)$ data samples. We present substantially improved measurements of the branching fraction $\mathcal{B}(\ensuremath{\Upsilon}(1S)\ensuremath{\rightarrow}J/\ensuremath{\psi}+X)$ using $J/\ensuremath{\psi}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ and $J/\ensuremath{\psi}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$ decays. The branching fractions for these two modes are averaged, thereby obtaining: $\mathcal{B}(\ensuremath{\Upsilon}(1S)\ensuremath{\rightarrow}J/\ensuremath{\psi}+X)=(6.4\ifmmode\pm\else\textpm\fi{}0.4(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.6(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$. A greatly improved measurement of the $J/\ensuremath{\psi}$ momentum distribution is presented and indicates a spectrum which is much softer than predicted by the color-octet model and somewhat softer than the color-singlet model. First measurements of the $J/\ensuremath{\psi}$ polarization and production angle are also presented. In addition, we report on the first observation of $\ensuremath{\Upsilon}(1S)\ensuremath{\rightarrow}\ensuremath{\psi}(2S)+X$ and evidence for $\ensuremath{\Upsilon}(1S)\ensuremath{\rightarrow}{\ensuremath{\chi}}_{cJ}+X$. Their branching fractions are measured relative to $\mathcal{B}(\ensuremath{\Upsilon}(1S)\ensuremath{\rightarrow}J/\ensuremath{\psi}+X)$ and are found to be ${[\mathcal{B}(\ensuremath{\Upsilon}(1S)\ensuremath{\rightarrow}\ensuremath{\psi}(2S)+X)]/[\mathcal{B}(\ensuremath{\Upsilon}(1S)\ensuremath{\rightarrow}J/\ensuremath{\psi}+\phantom{\rule{0ex}{0ex}}X)]}=0.41\ifmmode\pm\else\textpm\fi{}0.11(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.08(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})$, ${[\mathcal{B}(\ensuremath{\Upsilon}(1S)\ensuremath{\rightarrow}{\ensuremath{\chi}}_{c1}+X)]/[\mathcal{B}(\ensuremath{\Upsilon}(1S)\ensuremath{\rightarrow}J/\ensuremath{\psi}+X)]}=0.35\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0ex}{0ex}}0.08(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.06(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})$, ${[\mathcal{B}(\ensuremath{\Upsilon}(1S)\ensuremath{\rightarrow}{\ensuremath{\chi}}_{c2}+X)]/[\mathcal{B}(\ensuremath{\Upsilon}(1S)\ensuremath{\rightarrow}J/\ensuremath{\psi}+X)]}=0.52\ifmmode\pm\else\textpm\fi{}0.12(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.09(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})$, and ${[\mathcal{B}(\ensuremath{\Upsilon}(1S)\ensuremath{\rightarrow}{\ensuremath{\chi}}_{c0}+X)]/[\mathcal{B}(\ensuremath{\Upsilon}(1S)\ensuremath{\rightarrow}J/\ensuremath{\psi}+X)]}l7.4$ at 90% confidence level. The resulting feed-down contributions to $J/\ensuremath{\psi}$ are $[24\ifmmode\pm\else\textpm\fi{}6(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\ifmmode\pm\else\textpm\fi{}5(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})]%$ for $\ensuremath{\psi}(2S)$, $[11\ifmmode\pm\else\textpm\fi{}3(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\ifmmode\pm\else\textpm\fi{}2(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})]%$ for ${\ensuremath{\chi}}_{c1}$, $[10\ifmmode\pm\else\textpm\fi{}2(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\ifmmode\pm\else\textpm\fi{}2(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})]%$ for ${\ensuremath{\chi}}_{c2}$, and $l8.2%$ at 90% confidence level for ${\ensuremath{\chi}}_{c0}$. These measurements (apart from ${\ensuremath{\chi}}_{c0}$) are about a factor of 2 larger than expected based on the color-octet model.