Atomic parity nonconservation and neutron radii in cesium isotopes

The interpretation of future precise experiments on atomic parity violation in terms of parameters of the standard model could be hampered by uncertainties in the atomic and nuclear structure. While the former can be overcome by measurement in a series of isotopes, the nuclear structure requires knowledge of the neutron density. We use the nuclear Hartree-Fock method, which includes deformation effects, to calculate the proton and neutron densities in Cs¹²⁵--Cs¹³⁹. We argue that the good agreement with the experimental charge radii binding energies, and ground-state spins signifies that the phenomenological nuclear force and the method of calculation that we use is adequate. Based on this agreement, and on calculations involving different effective interactions, we estimate the uncertainties in the differences of the neutron radii {δ}〈r²{〉}_{N,N{'}}$ and conclude that they cause uncertainties in the ratio of weak charges, the quantities determined in the atomic parity nonconservation experiments, of less than ${10}^{{{-}}3}$. Such an uncertainty, although to some extent model dependent, is safely smaller than the anticipated experimental error.