Dispersion Corrections to Electron Scattering With and Without Parity Violation
Mikhail Gorshteyn
University of Indiana at Bloomington
I give a brief overview of the current status of the theory of two-boson exchange
corrections to elastic electron scattering. As a practical application, I consider
the dispersion correction due to gamma Z exchange in the forward regime. In the
exact forward limit, this correction is fixed by a sum rule that involves the
gamma Z-interference "cross section", and can be calculated directly from
experimental data. In absence of such data, I discuss how inclusive electromagnetic
data may be used to predict the value of the dispersion correction to the weak
charge of the proton, and show how the model dependence of this procedure can be
estimated.