Search for the radiative decay η → π0γγ in the SND experiment at VEPP-2M

The eta --> pi (0)gamma gamma decay was investigated by the SND detector at VEPP-2M e(+)e(-) collider in the reaction e(+)e(-) --> phi --> eta gamma. Here we present the results and some details of this study. We report an upper limit (90% c.l.) Br(eta --> pi (0)gamma gamma) < 8.4 x 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. (C) 2001 Elsevier Science B.V. All rights reserved.