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Strange Quark Contribution to the Nucleon Spin from Electroweak Elastic Scattering Data

The total contribution of strange quarks to the intrinsic spin of the nucleon can be determined from a measurement of the strange-quark contribution to the nucleon's elastic axial form factor. We have studied the strangeness contribution to the elastic vector and axial form factors of the nucleon, using all available elastic electroweak scattering data. Specifically, we combine elastic $νp$ and $\barν p$ scattering cross section data from the Brookhaven E734 experiment with elastic $ep$ and quasi-elastic $ed$ and $e$-$^4$He scattering parity-violating asymmetry data from the SAMPLE, HAPPEx, G0 and PVA4 experiments. We have not only determined these form factors at individual values of momentum-transfer ($Q^2$), as has been done recently, but also have fit the $Q^2$-dependence of these form factors using simple functional forms. We present the results of these fits using existing data, along with some expectations of how our knowledge of these form factors can be improved with data from the MicroBooNE experiment planned at Fermilab.