Search for the B→Y(4260)K, Y(4260)→J/ψπ+π− decays
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Abstract
We report the results of a search for the $B\ensuremath{\rightarrow}Y(4260)K$, $Y(4260)\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ decays. This study is based on a data sample corresponding to an integrated luminosity of $711\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$, collected at the $\mathrm{\ensuremath{\Upsilon}}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider. We investigate the $J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ invariant mass distribution in the range 4.0 to $4.6\text{ }\text{ }\mathrm{GeV}/{c}^{2}$ using both ${B}^{+}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{K}^{+}$ and ${B}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{K}_{S}^{0}$ decays. We find excesses of events above the background levels, with significances of 2.1 and 0.9 standard deviations for charged and neutral $B\ensuremath{\rightarrow}Y(4260)K$ decays, respectively, taking into account the systematic uncertainties. These correspond to upper limits on the product of branching fractions, $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}Y(4260){K}^{+})\ifmmode\times\else\texttimes\fi{}\mathcal{B}(Y(4260)\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})<1.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ and $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}Y(4260){K}^{0})\ifmmode\times\else\texttimes\fi{}\mathcal{B}(Y(4260)\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})<1.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ at the 90% confidence level.