[en] We extend the study of lowest moments, < x> and < x²>, of the parton distribution function of the nucleon to include those of the sea quarks; this entails a disconnected insertion calculation in lattice QCD. This is carried out on a 16³ x 24 quenched lattice with Wilson fermion. The quark loops are calculated with Z₂ noise vectors and unbiased subtractions, and multiple nucleon sources are employed to reduce the statistical errors. We obtain 5σ signals for < x> for the u,d, and s$ quarks, but < x²> is consistent with zero within errors. We provide results for both the connected and disconnected insertions. The perturbatively renormalized < x> for the strange quark at μ = 2 GeV is < x>_s+#bar s# = 0.027 ± 0.006 which is consistent with the experimental result. The ratio of < x> for s$ vs. u/d in the disconnected insertion with quark loops is calculated to be 0.88 ± 0.07. This is about twice as large as the phenomenologically fitted displays

[en] We present the N_f=2+1 clover fermion lattice QCD calculation of the nucleon strangeness form factors. We evaluate disconnected insertions using the Z(4) stochastic method, along with unbiased subtractions from the hopping parameter expansion. We find that increasing the number of nucleon sources for each configuration improves the signal significantly. We obtain G_M^s(0)=-0.017(25)(07), where the first error is statistical, and the second is the uncertainties in Q² and chiral extrapolations. This is consistent with experimental values, and has an order of magnitude smaller error.

[en] The calculation of the nucleon strangeness form factors from N_f = 2+1 clover fermion lattice QCD is presented. Disconnected insertions are evaluated using the Z(4) stochastic method, along with unbiased subtractions from the hopping parameter expansion. We find that increasing the number of nucleon sources for each configuration improves the signal significantly. We obtain G_M^s(0) = -0.017(25)(07), which is consistent with experimental values, and has an order of magnitude smaller error. Preliminary results for the strangeness contribution to the second moment of the parton distribution function are also presented.