Observation of Upsilon(4S) -˃ eta 'Upsilon(1S)

Abstract

We report the first observation of the hadronic transition Upsilon(4S) -> eta'Upsilon(1S), using 496 fb(-1) data collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We reconstruct the eta' meson through its decays to rho(0)Upsilon and to pi(+)pi(-)eta, with eta -> gamma gamma. We measure B(Upsilon(4S) -> eta'Upsilon(1S)) = [3.43 +/- 0.88(stat) +/- 0.21(syst)] x 10(-5), with a significance of 5.7 sigma.