Search for the decays ${\eta }^{\prime }\to e^{+}{e}^{-}$ and $\eta \to e^{+}{e}^{-}$ at the VEPP-2000 $e^{+}{e}^{-}$ collider

Abstract

A search for the rare decay ${\eta }^{\prime }\to e^{+}{e}^{-}$ has been performed with the SND detector at the VEPP-2000 $e^{+}{e}^{-}$ collider. The inverse reaction $e^{+}{e}^{-}\to {\eta }^{\prime }$ and ${\eta }^{\prime }$ five decay chains have been used for this search. The upper limit ${\Gamma }_{{\eta }^{\prime }\to e^{+}{e}^{-}}<0.002$ eV at the 90\% confidence level has been set. A sensitivity of SND in a search for $\eta \to e^{+}{e}^{-}$ decay has been studied. For this perpose we have analyzed a data sample with an integrated luminosity of 108 nb${}^{-1}$ collected in the center-of-mass energy range 520-580 MeV. There are no background events for the reaction $e^{+}{e}^{-}\to \eta$ with decay $\eta \to {\pi }^0{\pi }^0{\pi }^0$ have been found. In the absence of background, a sensitivity to $B(\eta \to e^{+}{e}^{-})$ of 10${}^{-6}$ can be reached during two weeks of VEPP-2000 operation.

arXiv comment4 pages, 4 figures. Prepared for the Proceedings of the PhiPsi15, Sep. 23-26, 2015, Hefei, China