Observation of the Leptonic Decay D+ →τ+ντ
Citation
Ablikim, M., Adlarson, P., Biernat, J., Ikegami Andersson, W., Johansson, T., Kupsc, A., ... & Zou, J. H. (2019). Observation of the Leptonic Decay D+-> T+ Yr. Physical Review Letters, 123(21).Abstract
We report the first observation of D+→τ+ντ with a significance of 5.1σ. We measure B(D+→τ+ντ)=(1.20±0.24stat±0.12syst)×10-3. Taking the world average B(D+→μ+νμ)=(3.74±0.17)×10-4, we obtain Rτ/μ=Γ(D+→τ+ντ)/Γ(D+→μ+νμ)=3.21±0.64stat±0.43syst., which is consistent with the standard model expectation of lepton flavor universality. Using external inputs, our results give values for the D+ decay constant fD+ and the Cabibbo-Kobayashi-Maskawa matrix element |Vcd| that are consistent with, but less precise than, other determinations. .
