Home > Publications database > Leptonic decay-constant ratio $f_K/f_\pi$ from lattice QCD using 2+1 clover-improved fermion flavors with 2-HEX smearing |
Journal Article | FZJ-2017-02609 |
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2017
Inst.
Woodbury, NY
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Please use a persistent id in citations: http://hdl.handle.net/2128/14132 doi:10.1103/PhysRevD.95.054513
Abstract: 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.
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