Electroproduction of Δ(1232) resonance at high momentum transfer

Jefferson Lab experiment E94-014 measured the the excitation of the Δ(1232) resonance at Q2 near 2.8 and 4 Gev2/c2 via the reaction p(e,e'p)π0. This is the highest Q2 for which exclusive resonance electroproduction has ever been observed. Decay distributions of the Δ(1232) resonance into the pπ0 final state were measured over a wide range of barycentric decay angles and energies. The goal of this experiment is to asses the transition in Q2 from the constituent quark model (CQM) to the regime where hard processes become important. At Q2∼few GeV2/c2 the ratio E1+/M1+ depends dramatically on the theoretical description, varying from a few 10-2 in the CQM limit, to about 1 in the pQCD limit. Preliminary analysis of the data shows that the ratio E1+/M1+ remains small at Q2 up to 4 Gev2/c2. After first pass analysis we obtain E1+/M1+=-4.1±1.2% at Q2=2.8 Gev2/c2 and E1+/M1+=-7.9±0.8% at Q2=4 Gev2/c2 (statistical errors only)