Leading isospin-breaking corrections to meson masses on the lattice

We present a study of the isospin-breaking (IB) corrections to pseudoscalar (PS) meson masses using the gauge configurations produced by the ETM Collaboration with N f = 2+1+1 dynamical quarks at three lattice spacings varying from 0.089 to 0.062 fm. Our method is based on a combined expansion of the path integral in powers of the small parameters and αem , where is the renormalized quark mass and αem the renormalized fine structure constant. We obtain results for the pion, kaon and Dmeson mass splitting; for the Dashen’s theorem violation parameters ϵγ (MM, 2 GeV), ϵπ 0 ϵK 0 (MS, 2 GeV) for the light quark masses for the flavour symmetry breaking parameters R(MS, 2 GeV) and Q (MS, 2 GeV) and for the strong IB effects on the kaon decay constants.