Strange quark contributions to nucleon mass and spin from lattice QCD
Contributions of strange quarks to the mass and spin of the nucleon, charac- terized by the observables fTs ands, respectively, are investigated within lattice QCD. The calculation employs a 2+1-flavor mixed-action lattice scheme, thus treating the strange quark degrees of freedom in dynamical fashion. Numerical results are obtained at three pion masses, mπ = 495MeV, 356MeV, and 293MeV, renormalized, and chirally extrapolated to the physical pion mass. The value ex- tracted fors at the physical pion mass in the MS scheme at a scale of 2GeV iss = −0.031(17), whereas the strange quark contribution to the nucleon mass amounts to fTs = 0.046(11). In the employed mixed-action scheme, the nucleon valence quarks as well as the strange quarks entering the nucleon matrix elements which determine fTs ands are realized as domain wall fermions, propagators of which are evaluated in MILC 2+1-flavor dynamical asqtad quark ensembles. The use of domain wall fermions leads to mild renormalization behavior which proves especially advantageous in the extraction of fTs.