Reduced uncertainty of the axial γZ-box diagram correction to the proton's weak charge

摘要

We present the fully up-to-date calculation of the γZ-box correction which needs to be taken into account to determine the weak mixing angle at low energies from parity-violating electron proton scattering. We make use of neutrino and antineutrino inclusive scattering data to predict the parity-violating structure function F_3~(γZ) by isospin symmetry. Our new analysis confirms previous results for the axial contribution to the γZ-box graph and reduces the uncertainty by a factor of 2. In addition, we note that the presence of parity-violating photon-hadron interactions induces an additional contribution via F_3~(γγ) . Using experimental and theoretical constraints on the nucleon anapole moment we are able to estimate the uncertainty associated with this contribution. We point out that future measurements are expected to significantly reduce this latter uncertainty.