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We present a lattice calculation of the electromagnetic (EM) effects on the masses of light pseudoscalar mesons. The simulations employ 2+1 dynamical flavors of asqtad QCD quarks, and quenched photons. Lattice spacings vary from $approx 0.12$ fm to $approx 0.045$ fm. We compute the quantity $epsilon$, which parameterizes the corrections to Dashens theorem for the $K^+$-$K^0$ EM mass splitting, as well as $epsilon_{K^0}$, which parameterizes the EM contribution to the mass of the $K^0$ itself. An extension of the nonperturbative EM renormalization scheme introduced by the BMW group is used in separating EM effects from isospin-violating quark mass effects. We correct for leading finite-volume effects in our realization of lattice electrodynamics in chiral perturbation theory, and remaining finite-volume errors are relatively small. While electroquenched effects are under control for $epsilon$, they are estimated only qualitatively for $epsilon_{K^0}$, and constitute one of the largest sources of uncertainty for that quantity. We find $epsilon = 0.78(1)_{rm stat}({}^{+phantom{1}8}_{-11})_{rm syst}$ and $epsilon_{K^0}=0.035(3)_{rm stat}(20)_{rm syst}$. We then use these results on 2+1+1 flavor pure QCD HISQ ensembles and find $m_u/m_d = 0.4529(48)_{rm stat}( {}_{-phantom{1}67}^{+150})_{rm syst}$.
We report on the MILC Collaboration calculation of electromagnetic effects on light pseudoscalar mesons. The simulations employ asqtad staggered dynamical quarks in QCD plus quenched photons, with lattice spacings varying from 0.12 to 0.06 fm. Finite
We present the first lattice-QCD calculation of the kaon valence-quark distribution functions using the large-momentum effective theory (LaMET) approach. The calculation is performed with multiple pion masses with the lightest one around 220 MeV, 2 l
We calculate pseudoscalar masses on gauge configurations containing the effects of 2+1 flavors of dynamical asqtad quarks and quenched electromagnetism. The lattice spacings vary from 0.12 to 0.06 fm. The masses are fit with staggered chiral perturba
Indirect CP violation in K rightarrow {pi}{pi} decays plays a central role in constraining the flavor structure of the Standard Model (SM) and in the search for new physics. For many years the leading uncertainty in the SM prediction of this phenomen
The rare kaon decays $Ktopiell^+ell^-$ and $Ktopi ubar{ u}$ are flavor changing neutral current (FCNC) processes and hence promising channels with which to probe the limits of the standard model and to look for signs of new physics. In this paper we