Study of Υ(3S, 2S) → ηΥ(1S) and Υ(3S, 2S) → π+π0 Υ(1S) Hadronic Transitions

We study the Υ(3S, 2S) → ηΥ(1S) and Υ(3S, 2S) → π+π-Υ(1S) transitions with 122 x 106 Υ(3S) and 100 x 106 Υ(2S) mesons collected by the BABAR detector at the PEP-II asymmetric-energy e+e- collider. We measure Β[Υ(2S) → ηΥ(1S)] = (2.39 ± 0.31(stat.) ± 0.14(syst.)) x 10-4 and Λ[Υ(2S) → ηΥ(1S)]/Λ[Υ(2S) → π+π-Υ(1S)] = (1.35 ± 0.17(stat.) ± 0.08(syst.)) x 10-3. We find no evidence for Υ(3S) → ηΥ(1S) and obtain Β[Υ(3S) → ηΥ(1S)] < 1.0 x 10-4 and Λ[Υ(3S) → ηΥ(1S)]/Λ[Υ(3S) → π+π-Υ(1S)] < 2.3 x 10-3 as upper limits at the 90% confidence level. We also provide improved measurements of the Υ(2S)-Υ(1S) and Υ(3S)-Υ(1S) mass differences, 562.170 ± 0.007(stat.) ± 0.088(syst.)MeV/c2 and 893.813 ± 0.015(stat.) ± 0.107(syst.)MeV/c2, respectively.