Electroproduction of theΔ(1232)Resonance at High Momentum Transfer

We studied the electroproduction of the $\Delta \left(1232\right)$ resonance via the reaction $p\left({e,e}^{\prime }p\right){\pi }^0$ at four-momentum transfers $Q^2=2.8\mathrm{}\mathrm{and}4.0{\mathrm{GeV}}^2$. This is the highest $Q^2$ for which exclusive resonance electroproduction has ever been observed. Decay angular distributions for $\Delta \to p{\pi }^0$ were measured over a wide range of barycentric energies covering the resonance. The $N–\Delta$ transition form factor $G_M^{*}$ and ratios of resonant multipoles $E_{1+}/M_{1+}$ and $S_{1+}/M_{1+}$ were extracted from the decay angular distributions. These ratios remain small, indicating that perturbative QCD is not applicable for this reaction at these momentum transfers.