6–11 Jul 2025
PALAIS DU PHARO, Marseille, France
Europe/Paris timezone

Precision measurement of the branching fraction for the decay $\psi(2S)\rightarrow\tau^{+}\tau^{-}$ at BESIII

10 Jul 2025, 09:55
17m
PALAIS DU PHARO, Marseille, France

PALAIS DU PHARO, Marseille, France

Parallel T05 - QCD and Hadronic Physics T05

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BESIII Collaboration

Description

Using $(2259.3 \pm 11.1)\times10^{6}$ $\psi(2S)$ events acquired with the BESIII detector, the branching fraction of $\psi(2S)\rightarrow\tau^{+}\tau^{-}$ is measured with improved precision to be
$\mathcal{B}_{\psi(2S)\rightarrow\tau^{+}\tau^{-}}=(3.240~\pm~0.023~\pm~0.081)\times 10^{-3}$, where the first and second uncertainties are statistical and systematic, respectively, which is consistent with the world average value within one standard deviation. This value, along with those for the branching fractions of the $\psi(2S)$ decaying into $e^{+}e^{-}$ and $\mu^{+}\mu^{-}$, is in good agreement with the relation predicted by the sequential lepton hypothesis. Combining the branching fraction values with the leptonic width of the $\psi(2S)$, the total width of the $\psi(2S)$ is determined to be (287 $\pm$ 9) keV.

Secondary track T06 - Top and Electroweak Physics

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