Parikshit Junnarkar, Andre Walker-Loud
The scalar strange-quark matrix element of the nucleon is computed with lattice QCD. A mixed-action scheme is used with domain-wall valence fermions computed on the staggered MILC sea-quark configurations. The matrix element is determined by making use of the Feynman-Hellmann Theorem which relates this strange matrix element to the change in the nucleon mass with respect to the strange quark mass. The final result of this calculation is m_s < N | s-bar s| N > = 49 +-10 +- 15 MeV which can be translated into f_s = m_s < N | s-bar s |N > / m_N = 0.053 +- 0.011 +- 0.016. Given the lack of a quantitative comparison of this phenomenologically important quantity determined from various lattice QCD calculations, we take the opportunity to present such an average. The resulting conservative determination is (all uncertainties added in quadrature) f_s = 0.043 +- 0.011 (99 % confidence interval).
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http://arxiv.org/abs/1301.1114
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