Precision measurement of the branching fraction for the decay ψ(2S)→τ⁺τ^-

2025/02/27 by BESIII Collaboration, M. Ablikim, Ablikim, M. +778
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #Neutrino Physics Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions

paper · pdf · doi:10.48550/arxiv.2502.19850

openalex publication_date 2025/02/27 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

Using (2259.3 ± 11.1)×10⁶ ψ(2S) events acquired with the BESIII detector, the branching fraction of ψ(2S)→τ⁺τ^- is measured with improved precision to be B_{ψ(2S)→τ⁺τ^-}=(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 one standard deviation. This value, along with those for the branching fractions of the ψ(2S) decaying into e⁺e^- and μ⁺μ^-, 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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