PREX Recent Results and Future Prospects

— The PREX experiment at Jefferson Lab has measured the parityviolating electroweak asymmetry in the elastic scattering of polarized electrons from Pb at an energy of 1.06 GeV and a scattering angle of 5◦. Since the Z0 boson couples mainly to neutrons, this asymmetry provides a clean measurement of the neutron RMS radius Rn of the lead nucleus. In addition to being a fundamental test of nuclear models, a precise measurement of Rn pins down the density dependence of the symmetry energy of neutron rich nuclear matter, which has impacts on neutron star structure, heavy ion collisions, and atomic parity violation experiments. The asymmetry from the first measurements performed in 2010 is Apv = 657±60(stat)± 13(syst) ppb at Q = 0.00906 GeV/c. Prospects for follow-up experiments with Pb and Ca are discussed.