We report a precision measurement of the parity-violating asymmetry APV in the elastic scattering of longitudinally polarized electrons from Pb208. We measure APV=550±16(stat)±8(syst) parts per billion, leading to an extraction of the neutral weak form factor FW(Q2=0.00616 GeV2)=0.368±0.013. Combined with our previous measurement, the extracted neutron skin thickness is Rn-Rp=0.283±0.071 fm. The result also yields the first significant direct measurement of the interior weak density of Pb208: ρW0=-0.0796±0.0036(exp)±0.0013(theo) fm-3 leading to the interior baryon density ρb0=0.1480±0.0036(exp)±0.0013(theo) fm-3. The measurement accurately constrains the density dependence of the symmetry energy of nuclear matter near saturation density, with implications for the size and composition of neutron stars.
ASJC Scopus subject areas
- Physics and Astronomy(all)