A concept for the experimental determination of the nucleon electric to magnetic form factor ratio at very low $Q^2$

Abstract

Stationary target measurements of the nucleon form factors have been performed with high precision down to $Q^2$ of $\sim$ 0.01 GeV$^2$ for protons ($G_E^p$) and down to $\sim$ 0.1 GeV$^2$ for neutrons ($G_M^n$). Conventional extraction using cross section and polarization measurement cannot be extended to very low values of $Q^2$ due to inherent experimental limitations. We present a proposal for a new approach to a measurement, using colliding beams, which will extend the range of possible measurement at low $Q^2$ by several orders of magnitude over stationary target limits.