γZ box corrections to weak charges of heavy nuclei in atomic parity violation.

We present a new dispersive formulation of the γZ box radiative corrections to weak charges of bound protons and neutrons in atomic parity violation measurements on heavy nuclei such as 133Cs and 213Ra. We evaluate for the first time a small but important additional correction arising from Pauli blocking of nucleons in a heavy nucleus. Overall, we find a significant shift in the γZ correction to the weak charge of 133Cs, approximately 4 times larger than the current uncertainty on the value of sin2 θ(W), but with a reduced error compared to earlier estimates.