Recent Results in Parity-Violating Electron Scattering at Jefferson Lab: PREX and HAPPEX-III

The parity-violating asymmetry $A_{PV}$ in electron scattering from the $^{208}$Pb nucleus is cleanly sensitive to the neutron radius $R_n$. A precision measurement of $R_n$ would have important implications for the understanding of nuclear structure, and be a powerful constraint on the symmetry energy $S_{\nu}(n)$ of neutron-rich nuclear matter, including neutron stars. The PREX collaboration has completed a first run, measuring $R_{n}$ to a precision of $\sim2.5$\% and providing the first electroweak evidence for the neutron skin of a heavy nucleus. Results from this measurement, and prospects for more precise future measurements, will be discussed.