New Measurements of the Low $Q^2$ Behavior of the $\gamma^*p\rightarrow\Delta$ Reaction

Data were taken using a polarized electron beam at the Mainz Microtron for the $ p(\vec{e}, e^{'} p)\pi^{0}$ reaction in the $\Delta$ region at $Q^{2} = 0.06~{\rm GeV}^{2}$ utilizing out of plane magnetic spectrometers. Results for the EMR = E2/M1 and CMR = C2/M1 ratios and the magnitude of the M1 amplitude will be shown and compared with reaction models. Non-zero quadrupole amplitudes demonstrate non-spherical components in nucleon and $\Delta$ structure. The data test the dynamical model descriptions of the $Q^2$ evolution in the long range, low $Q^2$ region where the pion cloud is predicted to be primarily responsible for non-spherical structure components. The EMR and CMR are extracted using resonant multipole fits of the separated cross sections $\sigma_{0} \equiv \sigma_{T} + \epsilon \sigma_{L}, \sigma_{TL}, \sigma_{TT}$. Background multipoles are tested through measurement of the fifth structure function $\sigma_{TL^{'}}$. The experiment was performed by an Athens, Mainz A1, and MIT collaboration.