Phys. Rev. D 87, 032006 (2013) - Search for $\ensuremath{\eta}$ and ${\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\mathbf{+}}{e}^{\mathbf{\ensuremath{-}}}{\overline{\ensuremath{\nu}}}_{e}\mathbf{+}\mathbf{c}.\mathbf{c}.$ decays in $J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\phi}\ensuremath{\eta}$ and $\ensuremath{\phi}{\ensuremath{\eta}}^{\ensuremath{'}}$

Search for $η$ and $η^{'} \to π^{+} e^{-} {\bar{ν}}_{e} + c . c .$ decays in $J / ψ \to ϕ η$ and $ϕ η^{'}$

M. Ablikim et al. (BESIII Collaboration)

Phys. Rev. D 87, 032006 – Published 15 February 2013

Abstract

Using a sample of 225.3 million $J / ψ$ events collected with the BESIII detector at the BEPCII $e^{+} e^{-}$ collider in 2009, searches for the decays of $η$ and $η^{'} \to π^{+} e^{-} {\bar{ν}}_{e} + c . c .$ in $J / ψ \to ϕ η$ and $ϕ η^{'}$ are performed. The $ϕ$ signals, which are reconstructed in $K^{+} K^{-}$ final states, are used to tag $η$ and $η^{'}$ semileptonic decays. No signals are observed for either $η$ or $η^{'}$ , and upper limits at the 90% confidence level are determined to be $7.3 \times 10^{- 4}$ and $5.0 \times 10^{- 4}$ for the ratios $\frac{B (η \to π^{+} e^{-} {\bar{ν}}_{e} + c . c .)}{B (η \to π^{+} π^{-} π^{0})}$ and $\frac{B (η^{'} \to π^{+} e^{-} {\bar{ν}}_{e} + c . c .)}{B (η^{'} \to π^{+} π^{-} η)}$ , respectively. These are the first upper-limit values determined for $η$ and $η^{'}$ semileptonic weak decays.