Search for the $\eta^{\prime}\to e^+e^-$ decay with the SND detector

TL;DR

This study searched for the rare decay of the eta prime meson into an electron-positron pair using the SND detector, setting an upper limit on its electronic width at 90% confidence level.

Contribution

First experimental search for the $\eta'$ to $e^+e^-$ decay at VEPP-2000, establishing a new upper limit on its electronic width.

Findings

No decay signal observed.

Upper limit on $\eta'$ electronic width set at 0.0020 eV.

Data collected at 957.78 MeV with 2.9 pb$^{-1}$ luminosity.

Abstract

A search for the process $e^+e^- \to \eta^\prime$ has been performed with the SND detector at the VEPP-2000 $e^+e^-$ collider. The data were accumulated at the center-of-mass energy of $957.78\pm 0.06$ MeV with an integrated luminosity of about 2.9 pb$^{-1}$. For reconstruction of the $\eta^\prime$ meson five decay chains have been used: $\eta^{\prime}\to\eta\pi^+\pi^-$ followed by the $\eta$ decays to $\gamma\gamma$ and $3\pi^0 $, and $\eta^{\prime} \to \eta\pi^0\pi^0$ followed by the $\eta$ decays to $\pi^+\pi^-\pi^0$, $\gamma\gamma$, and $3\pi^0$. As a result, the upper limit has been set on the $\eta^\prime$ electronic width: $\Gamma_{\eta^{\prime}\to e^+e^-} < 0.0020$ eV at the 90\% confidence level.