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Strange quark content of the nucleon and dark matter searches

The strange quark scalar content plays an important role in both the description of nucleon structure and in the determination of dark matter direct detection cross sections. As a measure of the strange-quark contribution to the nucleon mass, the strange-quark sigma term (σ_s) provides important insight into the nature of mass generation in QCD. The phenomenological determination of σ_s exhibits a wide range of variation, with values suggesting that the strange quark contributes anywhere between 0 and more than 30% of the nucleon mass. In the context of dark matter searches, coupled with relatively large Higgs coupling to strangeness, this variation dominates the uncertainty in predicted cross sections for a large class of dark matter models. Here we report on the recent results in lattice QCD, which are now giving a far more precise determination of σ_s than can be inferred from phenomenology. As a consequence, the lattice determinations of σ_s can now dramatically reduce the uncertainty in dark matter cross sections associated with the hadronic matrix elements.