Abstract

We report the observation of two narrow structures in the mass spectra of the pi+-Y(nS) (n=1,2,3) and pi+-hb(mP)(m$ (m=1,2) pairs that are produced in association with a single charged pion in Y(5S) decays. The measured masses and widths of the two structures averaged over the five final states are M_1=(10607.2+-2.0) MeV/c2, Gamma_1=(18.4+-2.4) MeV and M_2=(10652.2+-1.5) MeV/c2, Gamma_2=(11.5+-2.2) MeV. The results are obtained with a 121.4 1/fb data sample collected with the Belle detector in the vicinity of the Y(5S) resonance at the KEKB asymmetric-energy e+e- collider.