Searches for the decays η ′→ π 0 γγ and η ′ → ηγγ at the GAMS-4 π setup

Searches for the rare radiative decays η ′→ π 0 γγ and η ′ → η γγ were performed at the GAMS-4π setup. The following upper limits were set at a 90% confidence level: Br( η ′→ π 0 γγ ) < 6 × 10 -4 and Br( η ′→ ηγγ ) < 8×10 -4 . The π - p charge-exchange reaction at the beammomentum of 32.5GeV/ c was the source of 1.3 × 106 η ′ mesons. The measurements in questions were performed at the U-70 accelerator of the Institute for High Energy Physics (Protvino, Russia).