A lattice study of the strangeness content of the nucleon

We determine the quark contributions to the nucleon spin Δs, Δu and Δd as well as their contributions to the nucleon mass, the σ-terms. This is done by computing both, the quark line connected and disconnected contributions to the respective matrix elements, using the non-perturbatively improved Sheikholeslami-Wohlert Wilson Fermionic action. We simulate nF=2 mass degenerate sea quarks with a pion mass of about 285 MeV and a lattice spacing a≈0.073 fm. The renormalization of the matrix elements involves mixing between contributions from different quark flavours. The pion-nucleon σ-term is extrapolated to physical quark masses exploiting the sea quark mass dependence of the nucleon mass. We obtain the renormalized value σπN=(38±12) MeV at the physical point and the strangeness fraction fTs=σs/mN=0.012(14)−3+10 at our larger than physical sea quark mass. For the strangeness contribution to the nucleon spin we obtain ΔsMS¯(7.4GeV)=−0.020(10)(1).