The lead radius experiment PREX

The proposed PREX experiment at Jefferson Lab will measure the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons at an energy of 850 MeV and a scattering angle of 6°. Since the Z 0 boson couples mainly to neutrons, this asymmetry provides a clean measurement of R n with a projected experimental precision of ±1 %. In addition to being a fundamental test of nuclear theory, a precise measurement of R n 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.