Observation of Π (4S) →η′ Π (1S)

Abstract

We report the first observation of the hadronic transition Π(4S)→η′ Π (1S), using 496 fb-1 data collected at the Π (4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We reconstruct the η′ meson through its decays to ρ0γ and to π+π-η, with η→γγ. We measure B(Π(4S)→η′Π(1S))=[3.43±0.88(stat)±0.21(syst)]×10-5, with a significance of 5.7σ.