posted on 2012-03-01, 00:00authored byGregg Franklin, M. Friend, Diana Marwick Seymour Parno, Brian QuinnBrian Quinn, PREX Collaboration
We report the first measurement of the parity-violating asymmetry APV in the elastic scattering of polarized electrons from Pb208. APV is sensitive to the radius of the neutron distribution (Rn). The result APV=0.656±0.060(stat)±0.014(syst) ppm corresponds to a difference between the radii of the neutron and proton distributions Rn−Rp=0.33+0.16−0.18 fm and provides the first electroweak observation of the neutron skin which is expected in a heavy, neutron-rich nucleus.