New Formulation of yZ Box Corrections to the Weak Charge of the Proton

摘要

We present a new formulation of one of the major radiative corrections to the weak charge of the proton—that arising from the axial-vector hadron part of the γZ box diagram, (Ke⇔_γ~A)_Z This formulation, based on dispersion relations, relates the γZ contributions to moments of the (F_3~γ)~Z interference structure function. It has a clear connection to the pioneering work of Marciano and Sirlin, and enables a systematic approach to improved numerical precision. Using currently available data, the total correction from all intermediate states is (Ke⇔_γ~A)_Z = 0.0044(4) at zero energy, which shifts the theoretical estimate of the proton weak charge from 0.071 3(8) to 0.070 5(8). The energy dependence of this result, which is vital for interpreting the Q_(weak) experiment, is also determined.