Parity violating measurements of neutron densities - Jefferson Lab

Weak, Charge, and Point Radii
• Charge radius Rch is observable in (unpolarized)
elastic electron scattering. Rch 2 ≈Rp 2 +rp 2
• Weak radius RW is observable in parity violating
electron scattering. Define weak skin = RW - Rch
• Point proton Rp, neutron Rn radii, and neutron
skin = Rn - Rp are important for nuclear
structure (because nuclear forces are often
assumed to act on nucleon center of masses).
• Differences between charge/weak and point radii
from single nucleon E+M and weak form factors
(and from meson exchange currents ...).