Strange Nucleon Form Factors from $ep$ and $\nu p$ Elastic Scattering

Abstract

The recent parity-violating $ep$ forward-scattering elastic asymmetry data from Jefferson Lab (HAPPEx and G0), when combined with the $\nu p$ elastic cross section data from Brookhaven (E734), permit an extraction of the strangeness contribution to the vector and axial nucleon form factors for momentum transfers in the range $0.45 < Q^2 < 1.0$ GeV$^2$. These results, combined with the recent determination of the strange vector form factors at $Q^2 = 0.1$ GeV$^2$ (SAMPLE, HAPPEx, PVA4, G0) have been interpreted in terms of $uuds\bar{s}$ configurations very different from the kaon-loop configurations usually associated with strangeness in the nucleon. New experiments are being proposed to improve the state of our knowledge of the $\nu p$ elastic cross section -- these new experiments will push the range of $Q^2$ to much lower values, and greatly increase the precision of the $\nu p$ elastic data. One outcome of this can be a measurement of the strangeness contribution to the nucleon spin, $\Delta s$. Nuclear targets (e.g. C or Ar) are to be used in these neutrino experiments, and so a deep understanding of the nuclear physics, particularly in regard to final state effects, is needed before the potential of these precision experiments can be fully realized.