G0 Backward Angle Measurement: Strange Quark Contributions to Parity-Violating Asymmetries in Electron Scattering from LH2 and LD2 at $Q^2 \sim 0.63$ and $0.23$ GeV$^2$

The G0 backward angle experiment at Jefferson Lab completed running in March 2007. The experiment measured parity-violating asymmetries from backward scattered electrons in elastic electron-proton and quasi-elastic electron-deuteron interactions at momentum transfers of $Q^2=0.63$ and $0.23$ GeV$^2$. These asymmetries, arising from the interference of the electromagnetic and neutral weak interactions, are expected to be only a few tens of parts-per-million. The final asymmetries together with previous results, e.g. the G0 forward angle measurement [1], will allow for the determination of the strange quark contribution to the proton electric ($G_E^s$) and magnetic ($G_M^s$) form factors as well as the axial form factor ($G_A^e$) at the measured momentum transfers. The status of the experiment and the ongoing analysis of the data from both hydrogen and deuterium targets at beam energies of $687$ and $362$ MeV will be discussed. \newline \newline [1] D.S. Armstrong et al. (G0), {\it Phys. Rev. Lett.} {\bf 95}, 092001 (2005).