Measurement of the Neutron Radius of 208Pb Through Parity Violating in Electron Scattering

In contrast to the nuclear charge densities, which have been accurately measured with electron scattering, the knowledge of neutron densities still lack precision. Previous model-dependent hadron experiments suggest the difference between the neutron radius, R n , of a heavy nucleus and the proton radius, R p , to be in the order of several percent. To accurately obtain the difference, R n -R p , which is essentially a neutron skin, the Jefferson Lab Lead ( 208 Pb) Radius Experiment (PREX) measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from 208 Pb at an energy of 1.06 GeV and a scattering angle of 5 ◦ . Since Z 0 boson couples mainly to neutrons, this asymmetry provides a clean measurement of R n with respect to R p .

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