Electric Dipole Moments and Polarizability in the Quark-Diquark Model of the Neutron

For a bound state internal wave function respecting parity symmetry, it can be rigorously argued that the mean electric dipole moment must be strictly zero. Thus, both the neutron, viewed as a bound state of three quarks, and the water molecule, viewed as a bound state of ten electrons two protons and an oxygen nucleus, both have zero mean electric dipole moments. Yet, the water molecule is said to have a nonzero dipole moment strength $d=eLambda $ with $Lambda_{H_2O} approx 0.385 dot{A}$. The neutron may also be said to have an electric dipole moment strength with $Lambda_{neutron} approx 0.612 fm$. The neutron analysis can be made experimentally consistent, if one employs a quark-diquark model of neutron structure.