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 CollaborationwithNf=2+1+1 dynamical quarks at three lattice spacings varying from 0.089 to 0.062fm. Our method is based on a combined expansion of the path integral in powers of thesmall parameters (̂md−̂mu)/ΛQCDandαem, wherêmfis the renormalized quark mass andαemthe renormalized fine structure constant. We obtain results for the pion, kaon andD-meson mass splitting; for the Dashen’s theorem violation parametersγ(MS,2 GeV),π0,K0(MS,2 GeV); for the light quark masses (̂md−̂mu)(MS,2 GeV), (̂mu/̂md)(MS,2 GeV);for the flavour symmetry breaking parametersR(MS,2 GeV) andQ(MS,2 GeV) and forthe strong IB effects on the kaon decay constants