Electroexcitation of the Roper resonance for 1.7 en pi

The helicity amplitudes of the electroexcitation of the Roper resonance are extracted for 1.7 < Q 2 < 4.5 GeV 2 from recent high precision JLab-CLAS cross section and longitudinally polarized beam asymmetry data for π + electroproduction on protons at W = 1.15 - 1.69 GeV. The analysis is made using two approaches, dispersion relations and a unitary isobar model, which give consistent Q 2 behavior of the helicity amplitudes for the γ* p → N(1440)P 11 transition. It is found that the transverse helicity amplitude A 1/2 , which is large and negative at Q 2 = 0, becomes large and positive at Q 2 ≃ 2GeV 2 , and then drops slowly with Q 2 . The longitudinal helicity amplitude S 1/2 , which was previously found from CLAS ep → epπ 0 , enπ + data to be large and positive at Q 2 = 0.4, 0.65 GeV 2 , drops with Q 2 . Available model predictions for γ*p → N(1440)P 11 allow us to conclude that these results provide strong evidence in favor of N(1440)P 11 as a first radial excitation of the 3q ground state. The results of the present paper also confirm the conclusion of our previous analysis for Q 2 < 1 GeV 2 that the presentation of N(1440)P 11 as a q 3 G hybrid state is ruled out.