First measurement using elliptically polarized photons of the double-polarization observable $E$ for $\gamma p\to p{\pi }^0$ and $\gamma p\to n{\pi }^{+}$

A2 Collaboration, F. Afzal, K. Spieker +74

We report the measurement of the helicity asymmetry $E$ for the $p{\pi }^0$ and $n{\pi }^{+}$ final states using, for the first time, an elliptically polarized photon beam in combination with…