Strangeness and charmness content of nucleon from overlap fermions on 2+1-flavor domain-wall fermion configurations

We present a calculation of the strangeness and charmness contents <N|bar{s}s|N> and <N|bar{c}c|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 24^3*64 lattice with sea quark mass am_l=0.005, am_s=0.04, and inverse lattice spacing a^{-1}=1.73GeV. Both actions have chiral symmetry which is essential in avoiding contamination due to the operator mixing with other flavors. 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_{T_{s}} = m_s <N|bar{s}s|N> / M_N = 0.0334(62), and the charmness content f_{T_{c}} = m_c <N|bar{c}c|N> / M_N = 0.094(31) which is resolved from zero by 3sigma precision for the first time.