Search for the radiative decay $η\to π^0 γγ$ in the SND experiment at VEPP-2M

Abstract

The $η\to π^0 γγ$ decay was investigated by the SND detector at VEPP-2M $e^+e^-$ collider in the reaction $e^+e^-\toϕ\to ηγ$. Here we present the results and some details of this study. We report an upper limit (90% c.l.) $Br(η\to π^0 γγ)<8.4\times 10^{-4}$ as our final result. Our upper limit does not contradict the earlier measurement by GAMS spectrometer. To facilitate future studies a rather detailed review of the problem is also given.

24 pages, 6 figures, LaTex. To be published in Nucl. Phys. B