A measurement of the Compton scattering cross section during the PrimEx-II experiment at JLab*

The electron Compton scattering is the best known fundamental QED process, however, a precision measurement of its cross section for the beam energy above 1 GeV has been lacking up to now. An updated high precision measurement of the neutral pion lifetime via the Primakoff effect (PrimEx-II) experiment was performed in Hall B of Jefferson Lab in 2010. The experiment used small angle coherent photoproduction of $\pi^0$'s in the Coulomb field of a nucleus, $i.e.$ the Primakoff effet, to determin the lifetime with a precision of better than $1.5\%$ . It therefore requires thorough understanding of the underlying systematic uncertainties. To facilitate that data for well known electromagnetic processes were taken concurrently with the photoproduction data. We will present an analysis that pertains to measuring the Compton scattering cross section, which occurs at similar kinematics as the primary process. The combination of the well established theory of this process with large collected statistics allowed to extract this cross section with high precision in an energy region of 4-5 GeV for $^{12}C$ and $^{28}Si$ targets. The results of this analysis will be presented.