%0 Journal Article
%A Dürr, Stephan
%A Fodor, Zoltán
%A Hoelbling, Christian
%A Krieg, Stefan
%A Lellouch, Laurent
%A Lippert, Thomas
%A Rae, Thomas
%A Schäfer, Andreas
%A Scholz, Enno E.
%A Szabo, Kalman
%A Varnhorst, Lukas
%T Leptonic decay-constant ratio $f_K/f_\pi$ from lattice QCD using 2+1 clover-improved fermion flavors with 2-HEX smearing
%J Physical review / D
%V 95
%N 5
%@ 2470-0010
%C Woodbury, NY
%I Inst.
%M FZJ-2017-02609
%P 054513
%D 2017
%X We present a calculation of the leptonic decay-constant ratio $f_K/f_\pi$ in 2+1 flavor QCD, performed via a series of lattice studies, which allows us to quantify all sources of systematic uncertainty. Our final result is $f_K/f_\pi=1.182(28)$, and with isospin breaking corrections from ChPT the charged decay-constant ratio reads $f_{K^\pm}/f_{\pi^\pm}=1.178(28)$. With $V_\mathrm{ud}$ from super-allowed nuclear beta decays, the CKM matrix element $V_\mathrm{us}=0.2282(54)$ is perfectly compatible with the first-row unitarity constraint of the Standard Model.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000399145800003
%R 10.1103/PhysRevD.95.054513
%U https://juser.fz-juelich.de/record/828743