Abstract We present lattice results for fK/f f K / f π in the iso-symmetric limit of pure QCD (isoQCD) with Nf=2+1 N f = 2 + 1 flavours, along with a determination of |Vₔₒ|/|Vₔ₃| | V us | / | V ud | and a study on the unitarity of the first row of the Cabibbo–Kobayashi–Maskawa (CKM) matrix after introducing strong isospin-breaking and QED effects. The results obtained are based on a combination of a Wilson unitary action and the mixed-action setup introduced in Bussone et al. (Hadronic physics from a Wilson fermion mixed-action approach: setup and scale setting. http: //arxiv. org/abs/2510. 20450 ; Eur Phys J C 84: 506, 2024. http: //arxiv. org/abs/2309. 14154). The combination of the two regularisations enables a more precise control over the continuum-limit extrapolation.
Conigli et al. (Wed,) studied this question.