Strangeness and charmness content of the nucleon from overlap fermions on2+1-flavor domain-wall fermion configurations

We present a calculation of the strangeness and charmness contents ⟨N|s̄s|N⟩ and ⟨N|c̄c|N⟩ of the nucleon from dynamical lattice QCD with $2+1$ flavors. The calculation is performed with overlap valence quarks on $2+1$-flavor domain-wall fermion gauge configurations. The configurations are generated by the RBC collaboration on a 24³×64 lattice with sea-quark mass amₗ=0.005, amₛ=0.04, and inverse lattice spacing a^-1=1.73 GeV. Both actions have chiral symmetry which is essential in avoiding contamination due to the operator mixing with other flavors. The nucleon propagator and the quark loops are both computed with stochastic grid sources, while low-mode substitution and low-mode averaging methods are used respectively which substantially improve the signal-to-noise ratio. We obtain the strangeness matrix element f_Tₛ=mₛ⟨N|s̄s|N⟩/MN=0.0334(62), and the charmness content f_Tc=mc⟨N|c̄c|N⟩/MN=0.094(31) which is resolved from zero by 3σ precision for the first time.