Nucleon Sigma Terms with N_f = 2 + 1 O(a)-improved Wilson fermions

We present a lattice-QCD based analysis of the nucleon sigma terms using gauge ensembles with N_f = 2 + 1 flavors of O(a)-improved Wilson fermions, with a complete error budget concerning excited-state contaminations, the chiral interpolation as well as finite-size and lattice spacing effects. We compute the sigma terms determined directly from the matrix elements of the scalar currents. The chiral interpolation is based on SU(3) baryon chiral perturbation theory using the extended on-mass shell renormalization scheme. For the pion nucleon sigma term, we obtain σ_π N = (43.7±3.6) MeV, where the error includes our estimate of the aforementioned systematics. The tension with extractions based on dispersion theory persists at the 2.4-σ level. For the strange sigma term, we obtain a non-zero value, σ_s=(28.6±9.3) MeV.