Evidence for the η b ( 1 S ) Meson in Radiative Υ ( 2 S ) Decay
We have performed a search for the η b ( 1 S ) meson in the radiative decay of the Υ ( 2 S ) resonance using a sample of 91.6 × 10 6 Υ ( 2 S ) events recorded with the BABAR detector at the PEP-II B factory at the SLAC National Accelerator Laboratory. We observe a peak in the photon energy spectrum...
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Veröffentlicht in: | Physical review letters 2009-10, Vol.103 (16), Article 161801 |
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Sprache: | eng |
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Zusammenfassung: | We have performed a search for the η b ( 1 S ) meson in the radiative decay of the Υ ( 2 S ) resonance using a sample of 91.6 × 10 6 Υ ( 2 S ) events recorded with the BABAR detector at the PEP-II B factory at the SLAC National Accelerator Laboratory. We observe a peak in the photon energy spectrum at E γ = 609.3 + 4.6 − 4.5 ( stat ) ± 1.9 ( syst ) MeV , corresponding to an η b ( 1 S ) mass of 9394.2 + 4.8 − 4.9 ( stat ) ± 2.0 ( syst ) MeV / c 2 . The branching fraction for the decay Υ ( 2 S ) → γ η b ( 1 S ) is determined to be [ 3.9 ± 1.1 ( stat ) + 1.1 − 0.9 ( syst ) ] × 10 − 4 . We find the ratio of branching fractions B [ Υ ( 2 S ) → γ η b ( 1 S ) ] / B [ Υ ( 3 S ) → γ η b ( 1 S ) ] = 0.82 ± 0.24 ( stat ) + 0.20 − 0.19 ( syst ) . |
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ISSN: | 0031-9007 1079-7114 |
DOI: | 10.1103/PhysRevLett.103.161801 |