Electromagnetic contributions to pseudoscalar masses

Abstract

We report on the calculation by the MILC Collaboration of the electromagnetic effects on kaon and pion masses. These masses are computed in QCD with dynamical (asqtad staggered) quarks plus quenched photons at three lattice spacings varying from 0.12 to 0.06 fm. The masses are fit to staggered chiral perturbation theory with NLO electromagnetic terms, as well as analytic terms at higher order. We extrapolate the results to physical light-quark masses and to the continuum limit. At the current stage of the analysis, most, but not all, of the systematic errors have been estimated. The main goal is the comparison of kaon electromagnetic splittings to those of the pion, i.e., an evaluation of the corrections to "Dashen's theorem." This in turn will allow us to significantly reduce the systematic errors in our determination of m u /m d .

Up, down, strange and charm quark masses withNf=2+1+1twisted mass lattice QCD

“…Adopting the recent FLAG estimate MK + − MK 0 = −6.1(4) MeV [26], based on the results for the electromagnetic selfenergies in neutral and charged PS mesons obtained in Refs. [27,28,29,30,31,32], we find…”

Charmed and light pseudoscalar meson decay constants from four-flavor lattice QCD with physical light quarks

“…In Refs. [34,35], we found = 0.65(7)(14) (10), but this result did not yet adjust for finite volume effects on the photon field. A recent preliminary result [36] including finite volume effects is = 0.84 (21), and we use that here.…”

“…, where the subscript "QCD" indicates that the leading EM effects in the masses are removed from the experimental masses [30]. To remove these effects we use results from our ongoing lattice QED+QCD simulations with asqtad sea quarks [34,35] for the parameter that characterizes violations of Dashen's theorem:…”

“…In Ref. [35], the EM contribution to the squared K 0 mass was estimated to be about 900 MeV 2 . However, this estimate did not take into account the effects of EM quark mass renormalization, which should be subtracted from the result.…”

Isospin Splittings in the Light-Baryon Octet from Lattice QCD and QED

“…We find these corrections to be generically large. For instance, in boxes with L = 1.6-2.6 fm, which is the largest range of sizes considered in all but the preliminary work of [18] on pseudoscalar masses, the correction to ∆ QED M Ξ , the QED contribution to ∆M Ξ ≡ M Ξ 0 − M Ξ − , ranges from 123% to 76%. This is illustrated in Fig.…”