Abstract
We compute the light and strange quark masses mℓ=(mu+md)/2 and ms, respectively, in unquenched lattice QCD with Nf=2 flavours of light dynamical quarks. The renormalisation constants, which convert bare quark masses into renormalised quark masses, are computed nonperturbatively, including the effect of quark-line disconnected diagrams. We obtain mℓMS¯(2 GeV)=4.7(2)(3) MeV and msMS¯(2 GeV)=119(5)(8) MeV, using r0=0.467 fm to set the scale.
Highlights
The light and strange quark masses are among the least well known parameters of the Standard Model
For the lattice numbers to be useful for phenomenology, it is necessary to convert the bare quark masses to renormalized masses in some standard renormalization scheme
In full QCD a one-loop perturbative renormalization of the mass operator is totally inadequate even, as it does not account for the disconnected contribution shown in Fig. 1, which turns out to be comparable with the connected contribution at present lattice spacings
Summary
In quenched QCD, in which the effect of sea quarks is neglected (and quark-line disconnected fermion loops are absent), several groups [1] have carried out an entirely nonperturbative calculation of the light and strange quark masses. Previous calculations in full QCD, both with Nf = 2 [2] and Nf = 3 [3] flavors of sea quarks, employ perturbative renormalization to compute the relation between the bare and renormalized quark masses. In this Letter we shall present a first fully nonperturbative calculation of the light and strange quark masses in full QCD, including the effect of flavor singlet renormalization factors.
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