Search for $\eta$ and ${\eta }^{\prime }\to {\pi }^{+}{e}^{-}{\bar{\nu }}_e+c.c.$ decays in $\text{jpsi}\to \varphi \eta$ and $\varphi {\eta }^{\prime }$

Abstract

Using a sample of 225.3 million $\text{jpsi}$ events collected with the BESIII detector at the BEPCII $e^{+}{e}^{-}$ collider in 2009, searches for the decays of $\eta$ and ${\eta }^{\prime }\to {\pi }^{+}{e}^{-}{\bar{\nu }}_e+c.c.$ in $\text{jpsi}\to \varphi \eta$ and $\varphi {\eta }^{\prime }$ are performed. The $\varphi$ signals, which are reconstructed in $K^{+}{K}^{-}$ final states, are used to tag $\eta$ and ${\eta }^{\prime }$ semileptonic decays. No signals are observed for either $\eta$ or ${\eta }^{\prime }$, 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 $\frac{\mathcal{B}(\eta \to {\pi }^{+}{e}^{-}{\bar{\nu }}_e+c.c.)}{\mathcal{B}(\eta \to \text{pip}\text{pim}\text{piz})}$ and $\frac{\mathcal{B}({\eta }^{\prime }\to {\pi }^{+}{e}^{-}{\bar{\nu }}_e+c.c.)}{\mathcal{B}({\eta }^{\prime }\to \text{pip}\text{pim}\eta )}$, respectively. These are the first upper limit values determined for $\eta$ and ${\eta }^{\prime }$ semileptonic weak decays.

Comments: 8 pages, 4 figures; version accpeted for publication at PRD