Observation of the bottomonium ground state, eta_b, at BaBar

2008/09/09 by P. Grenier, Grenier, Philippe
Earth and Planetary Sciences · Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High-pressure geophysics and materials #Nuclear physics research studies #Quantum Chromodynamics and Particle Interactions

paper · pdf · doi:10.48550/arxiv.0809.1672

openalex publication_date 2008/09/09 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

We present the first observation of the bottomonium ground state eta_b(1S) in the photon energy spectrum using a sample of 109+/-1 million of Upsilon(3S) events recorded at the Upsilon(3S) energy with the BaBar detector at the PEP-II B factory at SLAC. A peak at E_gamma = 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 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/c2. The hyperfine Upsilon(1S)-eta_b(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)) x 10^(-4).

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