Observation of the bottomonium ground state, ηb, at BaBar
نویسنده
چکیده
We present the first observation of the bottomonium ground state ηb(1S) in the photon energy spectrum using a sample of (109 ± 1) million of Υ(3S) events recorded at the Υ(3S) energy with the BaBar detector at the PEP-II B factory at SLAC. A peak at Eγ = 921.2 +2.1 −2.8(stat) ± 2.4(syst) MeV observed with a significance of 10 standard deviations in the photon energy spectrum is interpretated as being due to the radiative transition Υ(3S) → γ ηb(1S). This photon energy corresponds to an ηb(1S) mass of 9388.9 +3.1 −2.3(stat) ± 2.7(syst) MeV/c2. The hyperfine Υ(1S)ηb(1S) mass splitting is 71.4 +2.3 −3.1(stat) ± 2.7(syst) MeV/c2. The branching fraction for this radiative Υ(3S) decay is obtained as (4.8± 0.5(stat) ± 1.2(syst))× 10−4.
منابع مشابه
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