Institute: MPI für Physik     Collection: YB 2016     Display Documents

ID: 715998.0, MPI für Physik / YB 2016
Measurement of branching fractions for B \\to J/\\psi \\eta K decays and search for a narrow resonance in the J/\\psi \\eta final state
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Audience:Not Specified
Intended Educational Use:No
Abstract / Description:We report an observation of the $B^{\\pm} \\to J/\\psi \\eta K^{\\pm}$ and $B^0 \\to J/\\psi \\eta K^0_S$ decays using 772$\\times 10^{6}$ $B\\bar{B}$ pairs collected at the $\\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We obtain the branching fractions ${\\cal B}(B^{\\pm}\\rightarrow J/\\psi\\eta K^{\\pm})=(1.27\\pm 0.11{\\rm (stat.)\\pm 0.11{\\rm (syst.)})}\\times10^{-4}$ and ${\\cal B}(B^0\\to J/\\psi \\eta K^0_S)=(5.22 \\pm 0.78 {\\rm(stat.)} \\pm 0.49{\\rm(syst.)})\\times10^{-5}$. We search for a new narrow charmonium(-like) state $X$ in the $J/\\psi \\eta$ mass spectrum and find no significant excess. We set upper limits on the product of branching fractions, ${\\cal B}(B^\\pm \\to XK^\\pm){\\cal B}(X \\to J/\\psi \\eta)$, at 3872 MeV$/c^2$ where a $C$-odd partner of X(3872) may exist, at $\\psi(4040)$ and $\\psi(4160)$ assuming their known mass and width, and over a range from 3.8 to 4.8 GeV$/c^2$. % at a 5 MeV$/c^2$ step. The obtained upper limits at 90% confidence level for $X^{C{\\rm -odd}}(3872)$, $\\psi(4040)$ and $\\psi(4160)$ are 3.8$\\times 10^{-6}$, 15.5$\\times 10^{-6}$ and 7.4$\\times 10^{-6}$, respectively.
Classification / Thesaurus:Belle II
Comment of the Author/Creator:Submitted to PTEP
Document Type:Article
Communicated by:MPI für Physik
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