New measurements ofΥ(1S)decays to charmonium final states

Abstract

Using data collected by the CLEO III detector at CESR, we report on measurements of ${\rm Y}(1S)$ decays to charmonium final states. The data sample used for this analysis consists of $21.2\times {10}^6$ ${\rm Y}(1S)$ decays, representing about 35 times more data than previous CLEO ${\rm Y}(1S)$ data samples. We present substantially improved measurements of the branching fraction $\mathcal{B}({\rm Y}(1S)\to J/\psi +X)$ using $J/\psi \to {\mu }^{+}{\mu }^{-}$ and $J/\psi \to e^{+}{e}^{-}$ decays. The branching fractions for these two modes are averaged, thereby obtaining: $\mathcal{B}({\rm Y}(1S)\to J/\psi +X)=(6.4\pm 0.4(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.6(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}))\times {10}^{-4}$. A greatly improved measurement of the $J/\psi$ 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 $J/\psi$ polarization and production angle are also presented. In addition, we report on the first observation of ${\rm Y}(1S)\to \psi (2S)+X$ and evidence for ${\rm Y}(1S)\to {\chi }_{cJ}+X$. Their branching fractions are measured relative to $\mathcal{B}({\rm Y}(1S)\to J/\psi +X)$ and are found to be $\{[\mathcal{B}({\rm Y}(1S)\to \psi (2S)+X)]/[\mathcal{B}({\rm Y}(1S)\to J/\psi +X)]\}=0.41\pm 0.11(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.08(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})$,

Keywords

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• INLINE
• HTTP
• FALSE
• MO STRETCHY
• XMLNS

Other Versions

• Version 2, 2004-07-16, preprints

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