Measurement of the Absolute Branching Fraction of Ds+ → τ+ντ via τ+ → e+νe¯ντ

• Published in: Physical review letters 2021-10, Vol.127 (17), p.1
• Main Author: Ablikim, M
• Format: Article
• Language: English
• Subjects: Flavor (particle physics); Leptons; Quantum chromodynamics; Quarks; Standard model (particle physics)
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.127.171801

Using a dataset of 6.32 fb−1 of e+e− annihilation data collected with the BESIII detector at center-of-mass energies between 4178 and 4226 MeV, we have measured the absolute branching fraction of the leptonic decay Ds+ → τ+ντ via τ+→ e+νe¯ντ , and find BDs+→τ+ντ= ( 5.27 ± 0.10 ± 0.12 ) × 10−2, where the first uncertainty is statistical and the second is systematic. The precision is improved by a factor of 2 compared to the previous best measurement. Combining with fDs+ from lattice quantum chromodynamics calculations or the |Vcs| from the CKMfitter group, we extract | Vcs| = 0.978 ± 0.009 ± 0.012 and fDs+ = ( 251.1 ± 2.4 ± 3.0 ) MeV , respectively. Combining our result with the world averages of BDs+→τ+ντ and BDs+→μ+νμ, we obtain the ratio of the branching fractions BDs+→τ+ντ/BDs+→μ+νμ= 9.72 ± 0.37 , which is consistent with the standard model prediction of lepton flavor universality.