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First Observation of Upsilon(3S) --> tau tau and Tests of Lepton Universality in Upsilon Decays

D. Besson·CLEO Collaboration
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Abstract

Using data collected with the CLEO-III detector at the CESR e+e- collider, we report on a first observation of the decay of the Upsilon(3S) to tau tau, and precisely measure the ratio of branching fractions of Upsilon(nS),n=1,2,3 to tau tau and mu mu final states, finding agreement with expectations from lepton universality. We derive absolute branching fractions for these decays, and also set a limit on the influence of a low mass CP-odd Higgs boson in the decay of the Upsilon(1S).

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D. Besson, CLEO Collaboration. 2007-03-27. First Observation of Upsilon(3S) --> tau tau and Tests of Lepton Universality in Upsilon Decays. https://doi.org/10.1103/physrevlett.98.052002

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