A lattice study of the strangeness content of the nucleon

作者：Bali G S^*; Collins S; Goeckeler M; Horsley R; Nakamura Y; Nobile A; Pleiter D; Rakow P E L; Sternbeck A; Schaefer A; Schierholz G; Zanotti J M

来源：Progress in Particle and Nuclear Physics, 2012, 67(2): 467-472.

DOI：10.1016/j.ppnp.2012.01.012

• Lattice QCD
• Nucleon structure
• Nucleon spin
• sigma-term
• Strangeness

We determine the quark contributions to the nucleon spin Delta s, Delta u and Ad as well as their contributions to the nucleon mass, the a-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 approximate to 0.073 fm. The renormalization of the matrix elements involves mixing between contributions from different quark flavours. The pion-nucleon a-term is extrapolated to physical quark masses exploiting the sea quark mass dependence of the nucleon mass. We obtain the renormalized value sigma(pi N) = (38 +/- 12) MeV at the physical point and the strangeness fraction f(Ts) = sigma s/m(N) = 0.012(14)(-3)(+10) at our larger than physical sea quark mass. For the strangeness contribution to the nucleon spin we obtain Delta s ((MS)) over bar(root 7.4 GeV) = -0.020(10)(1).

• 出版日期2012-4