First observation of the decay φ→η′(958)γ

The decay φ → η ′ γ has been observed by the CMD-2 detector at the e + e − collider VEPP-2M at Novosibirsk. Of 5.5 million produced φ 's, six events of the φ → η ′ γ decay were selected with the expected background less than one event. The corresponding branching ratio is B( φ → η ′ γ )=1.2 +0.7 −0.5 ·10 −4 . It is the first observation of this radiative decay.