Electroproduction of the Delta (1232) resonance at high momentum transfer

Jefferson Lab experiment E94-014 measured the excitation of the Delta (1232) resonance via the reaction p(e,e{prime}p){pi}{sup 0} at Q{sup 2} near 2.8 and 4 Gev{sup 2}. This is the highest Q{sup 2} for which exclusive resonance electroproduction has ever been observed. Decay distributions of the Delta (1232) resonance into the ppi{sup 0} final state were measured over a wide range of barycentric decay angles and energies. The goal of this experiment is to assess the transition in Q{sup 2} from the constituent quark model (CQM) to the regime where hard processes become important. At Q{sup 2} {approx} few GeV{sup 2}/c{sup 2} the ratio E{sub 1+}/M{sub 1+} depends dramatically on the theoretical description, varying from a few 10{sup -2} in the CQM limit, to about 1 in the pQCD limit. Preliminary analysis of the data shows that the ratio E{sub 1+}/M{sub 1+} remains small at Q{sup 2} up to 4 Gev{sup 2}/c{sup 2}. After first pass analysis we obtain E{sub 1+}/M{sub 1+} = -4.1 {+-} 1.2 at Q{sup 2} = 2.8 Gev{sup 2}/c{sup 2} and E{sub 1+}/M{sub 1+} = -7.9 {+-} 0.8 at Q{sup 2} = 4 Gev{sup 2}/c{sup 2} (statistical errors only).