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Published May 14, 2010 | Published
Journal Article Open

Test of Lepton Universality in Υ(1S) Decays at BABAR


The ratio R_(τμ)(Υ(1S)) = Γ_(Υ(1S)→τ^+^τ-)/Γ_(Υ(1S)→μ^+μ^-) is measured using a sample of (121.8±1.2) × 10^(6)Υ(3S) events recorded by the BABAR detector. This measurement is intended as a test of lepton universality and as a search for a possible light pseudoscalar Higgs boson. In the standard model (SM) this ratio is expected to be close to 1. Any significant deviations would violate lepton universality and could be introduced by the coupling to a light pseudoscalar Higgs boson. The analysis studies the decays Υ(3S)→Υ(1S)π^+π^-, Υ(1S)→l^+l^-, where l = μ, τ. The result, R_(τμ)(Υ(1S)) = 1.005±0.013(stat)±0.022(syst), shows no deviation from the expected SM value, while improving the precision with respect to previous measurements.

Additional Information

© 2010 American Physical Society. Received 24 February 2010; published 14 May 2010. We are grateful for the excellent luminosity and machine conditions provided by our PEP-II colleagues, and for the substantial dedicated effort from the computing organizations that support BABAR. The collaborating institutions wish to thank SLAC for its support and kind hospitality. This work is supported by DOE and NSF (USA), NSERC (Canada), CEA and CNRS-IN2P3 (France), BMBF and DFG (Germany), INFN (Italy), FOM (The Netherlands), NFR (Norway), MES (Russia), MEC (Spain), and STFC (United Kingdom). Individuals have received support from the Marie Curie EIF (European Union) and the A. P. Sloan Foundation.

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Published - Sanchez2010p10195Phys_Rev_Lett.pdf


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