First Measurement of the Double Spin Asymmetry in $\overrightarrow{\mathit{e}}\overrightarrow{\mathit{p}}\to {\mathit{e}}^{\prime }{\pi }^{+}\mathit{n}$ in the Resonance Region

The double spin asymmetry in the $\overrightarrow{e}\overrightarrow{p}\to e^{\prime }{\pi }^{+}n$ reaction has been measured for the first time in the resonance region for four-momentum transfer $Q^2=0.35\mathrm{}–1.5{\mathrm{GeV}}^2$. Data were taken at Jefferson Lab with the CLAS detector using a 2.6 GeV polarized electron beam incident on a polarized solid ${\mathrm{NH}}_3$ target. Comparison with predictions of phenomenological models shows strong sensitivity to resonance contributions. Helicity- $1/2$ transitions are found to be dominant in the second and third resonance regions. The measured asymmetry is consistent with a faster rise with $Q^2$ of the helicity asymmetry $A_1$ for the $F_{15}\left(1680\right)$ resonance than expected from the analysis of the unpolarized data.