Wednesday, October 1, 2008, 11:00 am — Small Seminar Room, Bldg. 510
We report the results of a search for the bottomonium ground state eta_b(1S)
in the photon energy spectrum with a sample of (109 ± 1) million of Upsilon(3S)
recorded at the Upsilon(3S) energy with the BABAR detector at the PEP-II B factory at SLAC.
We observe a peak in the photon energy spectrum at E_gamma = 921.2 +2.1 -2.8 (stat) ± 2.4(syst) MeV
with a significance of 10 standard deviations. We interpret the observed peak as being due to
monochromatic photons from the radiative transition Upsilon(3S) -> gamma eta_b(1S).
This photon energy corresponds to an eta_b(1S) mass of 9388.9 +3.1 -2.3 (stat) ± 2.7(syst) MeV/c^2.
The hyperfine Upsilon(1S)-eta_b(1S) mass splitting is 71.4 +2.3 -3.1 (stat) ± 2.7(syst) MeV/c^2.
The branching fraction for this radiative Upsilon(3S) decay is estimated to be
(4.8 ± 0.5(stat) ± 1.2 (syst)) x 10^(-4).
Hosted by: Mary Bishai
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