We report evidence for the ground state of bottomonium, ηb(1S), in the radiative decay Υ(3S)→γηb in e+e- annihilation data taken with the CLEO III detector. Using 6×106 Υ(3S) decays, and assuming Γ(ηb)=10±5MeV/c2, we obtain B(Υ(3S)→γηb)=(7.1±1.8±1.3)×10 -4, where the first error is statistical and the second is systematic. The statistical significance is ∼4σ. The mass is determined to be M(ηb)=9391.8±6.6±2.0MeV/c2, which corresponds to the hyperfine splitting ΔMhf(1S)b=68.5±6.6±2.0MeV/c2. Using 9×106 Υ(2S) decays, we place an upper limit on the corresponding Υ(2S) decay, B(Υ(2S)→γηb)<8. 4×10-4 at 90% confidence level.
|Original language||English (US)|
|Journal||Physical Review D - Particles, Fields, Gravitation and Cosmology|
|State||Published - Feb 24 2010|