Nucleon strange quark content from Nf=2+1 lattice QCD with exact chiral symmetry

Abstract

We calculate the strange quark content of the nucleon in 2+1 -flavor lattice QCD. Chirally symmetric overlap fermion formulation is used to avoid the contamination from up and down quark contents due to an operator mixing between strange and light scalar operators, s̄s and ūu+d̄d. At a lattice spacing a=0.112(1) fm, we perform calculations at four values of degenerate up and down quark masses mud, which cover a range of the pion mass Mπ 300-540 MeV. We employ two different methods to calculate;. One is a direct method where we calculate by directly inserting the s̄s operator. The other is an indirect method where is extracted from a derivative of the nucleon mass in terms of the strange quark mass. With these two methods we obtain consistent results for with each other. Our best estimate fTs=ms /MN=0.009(15) stat(16)sys is in good agreement with our previous studies in two-flavor QCD. © 2013 American Physical Society.