Measurement of the Branching Fraction for D+ₛ→τ⁺ντ and Extraction of the Decay Constant fDₛ

الأصل · EN

The branching fraction for the decay D+ₛ→τ⁺ντ, with τ⁺→ e⁺ νₑντ, is measured using a data sample corresponding to an integrated luminosity of 427 fb⁻¹ collected at center of mass energies near 10.58 GeV with the B-0.1em A-0.1em B-0.1em A-0.2em R detector at the PEP-II asymmetric-energy e⁺e⁻ collider at SLAC. In the process e⁺e⁻→ c c→ D*⁺ₛ 0.2em -0.2em DTAG 0.2em -0.2em K X, the D*⁺ₛ meson is reconstructed as a missing particle, and the subsequent decay D*⁺ₛ→ D+ₛγ yields an inclusive D+ₛ data sample. Here TAG refers to a fully reconstructed hadronic 0.2em -0.2em D decay, 0.2em -0.2em K is a K- or 0.2em -0.2em K⁰, and X stands for any number of charged or neutral pions. The decay D+ₛ→ K⁰ S K⁺ is isolated also, and from ratio of event yields and known branching fractions, B (D+ₛ→τ⁺ντ) = (4.5±0.5±0.4±0.3% is determined. The pseudoscalar decay constant is extracted to be fDₛ = (233±13±10±7) MeV, where the first uncertainty is statistical, the second is systematic, and the third results from the uncertainties on the external measurements used as input to the calculation.