Speaker
Jianyong ZHANG
(IHEP)
Description
Using （2259.3 +/-11.1） ×106 ψ（2S） events acquired with the BESIII detector, the branching fraction ofψ（2S） → ττ is measured with improved precision to be（3.240+/- 0.023 +/-0.081） × 10−3, where the first and second uncertainties are statistical and systematic, respectively, which is consistent with the world average value within 1 standard deviation. This value, along with those for the branching fractions of the ψ(2S) decaying into ee and μμ, is in good agreement with the relation predicted by the sequential lepton hypothesis. Combining the branching fraction values with the leptonic width of the ψ(2S), the total width of the ψ(2S) is determined to be （287+/- 9） keV.
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Primary author
Jianyong ZHANG
(IHEP)
