αs and |Vcs| determination, and CKM unitarity test, from W decays at NNLO

The hadronic (Gamma(W)(had)) and total (Gamma(W)(tot)) widths of the W boson, computed at least at next- to- next- to- leadingorder (NNLO) accuracy, are combined to derive a new precise prediction for the hadronic W branching ratio B-had(W)= Gamma(W)(had)/ Gamma(W)(tot)= 0.682 +/- 0.011par, using the experimental Cabibbo- Kobayashi- Maskawa (CKM) matrix elements, with uncertainties dominated by the input parameters of the calculations, or B-had(W) = 0.6742 +/- 0.0002(th) +/- 0.0001(par) assuming CKM unitarity. Comparing the theoretical predictions and experimental measurements for various W decay observables, the NNLO strong coupling constant at the Z pole, as(m(2)Z) = 0.117 +/- 0.042(exp)+/- 0.004(th)+/- 0.001(par), as well as the charm- strange CKM element, |V-cs| = 0.973 +/- 0.004(exp) +/- 0.002(par), can be extracted under different assumptions. We also show that W decays provide today the most precise test of CKM unitarity for the 5 quarks lighter than mW, Sigma(u, c, d, s, b) |V-ij|(2)= 1.999 +/- 0.008exp+/- 0.001th. Perspectives for asand | Vcs| extractions from W decays measurements at the LHC and future e(+) e(-) colliders are presented. (C) 2016 The Authors. Published by Elsevier B. V.