Thursday, January 10, 2013

1301.1765 (R. D. Young)

Strange quark content of the nucleon and dark matter searches    [PDF]

R. D. Young
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 (\sigma_s) provides important insight into the nature of mass generation in QCD. The phenomenological determination of \sigma_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 \sigma_s than can be inferred from phenomenology. As a consequence, the lattice determinations of \sigma_s can now dramatically reduce the uncertainty in dark matter cross sections associated with the hadronic matrix elements.
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