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

• Received 18 January 2019

DOI:https://doi.org/10.1103/PhysRevD.99.071102

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Published by the American Physical Society