A lattice study of the strangeness content of the nucleon

Abstract

We determine the quark contributions to the nucleon spin Delta s, Delta u and Delta d as well as their contributions to the nucleon mass, the sigma-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 n_F=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 sigma-term is extrapolated to physical quark masses exploiting the sea quark mass dependence of the nucleon mass. We obtain the renormalized value sigma_{piN}=38(12) MeV at the physical point and the strangeness fraction f_{Ts}=sigma_s/m_N=0.012(14)(+10-3) at our larger than physical sea quark mass. For the strangeness contribution to the nucleon spin we obtain in the MSbar scheme at the renormalization scale of 2.71 GeV Delta s = -0.020(10)(2).

7 pages, 3 figures, Invited Talk at the 33rd Erice School on Nuclear Physics, Erice, 16-24 September 2011, Italy

References in corpus (3)

• Extraction of Spin-Dependent Parton Densities and Their Uncertainties
• Two-loop renormalization of vector, axial-vector and tensor fermion bilinears on the lattice
• Nucleon strange quark content from two-flavor lattice QCD with exact chiral symmetry

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• Sea Quark and Gluon contributions to Strange Baryons and their Properties
• Expansion coefficient of the pseudo-scalar density using the gradient flow in lattice QCD