Measurement of the absolute branching fractions for purely leptonic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msubsup><mml:mi>D</mml:mi><mml:mi>s</mml:mi><mml:mo>+</mml:mo></mml:msubsup></mml:math> decays

We report new measurements of the branching fraction B(Ds+→ℓ+ν), where ℓ+ is either μ+ or τ+(→π+ν¯τ), based on 6.32 fb−1 electron-positron annihilation data collected by BESIII experiment at six center-of-mass energy points between 4.178 and 4.226 GeV. Simultaneously floating Ds+→μ+νμ Ds+→τ+ντ components yields B(Ds+→τ+ντ)=(5.21±0.25±0.17)×10−2, B(Ds+→μ+νμ)=(5.35±0.13±0.16)×10−3, ratio decay widths R=Γ(Ds+→τ+ντ)Γ(Ds+→μ+νμ)=9.73−0.58+0.61±0.36, first uncertainties are statistical second systematic. No evidence CP asymmetry observed in rates Ds±→μ±νμ Ds±→τ±ντ: ACP(μ±ν)=(−1.2±2.5±1.0)% ACP(τ±ν)=(+2.9±4.8±1.0)%. Constraining our measurement to Standard Model expectation lepton universality (R=9.75), we find more precise results B(Ds+→τ+ντ)=(5.22±0.10±0.14)×10−2 ACP(τ±ντ)=(−0.1±1.9±1.0)%. Combining with inputs external analysis, determine c→s¯ quark mixing matrix element, Ds+ constant, constants be |Vcs|=0.973±0.009±0.014, fDs+=249.9±2.4±3.5 MeV, fDs+/fD+=1.232±0.035, respectively.1 MoreReceived 23 February 2021Accepted 27 July 2021DOI:https://doi.org/10.1103/PhysRevD.104.052009Published American Physical Society under terms Creative Commons Attribution 4.0 International license. Further distribution this work must maintain attribution author(s) published article’s title, journal citation, DOI. Funded SCOAP3.Published SocietyPhysics Subject Headings (PhySH)Research AreasElectroweak interactionParticles & Fields