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, have zero mean electric dipole moments. Yet, the water molecules are said to have a nonzero dipole moment strength d = e Lambda with Lambda(H2O) approximate to 0.385 angstrom. The neutron may also be said to have an electric dipole moment strength with Lambda(neutron) approximate to 0.612 fm. The neutron analysis can be made experimentally consistent, if one employs a quark-diquark model of neutron structure.