Experimental study of the P11(1440) and D13(1520) resonances from the CLAS data on ep → e′π+π-p′

The transition helicity amplitudes from the proton ground state to the P-11(1440) and D-13(1520) excited states (gamma(v)pN* electrocouplings) were determined from the analysis of nine independent one-fold differential pi(+)pi(-)p electroproduction cross sections off a proton target, taken with CLAS at photon virtualities of 0.25 < Q(2) < 0.60 GeV2. The phenomenological reaction model was employed for separation of the resonant and nonresonant contributions to the final state. The P-11(1440) and D-13(1520) electrocouplings were obtained from the resonant amplitudes parametrized within the framework of a unitarized Breit-Wigner ansatz. They are consistent with results obtained in the previous CLAS analyses of the pi(+)n and pi(0)p channels. The successful description of a large body of data in dominant meson-electroproduction channels off protons with the same gamma(v)pN* electrocouplings offers clear evidence for the reliable extraction of these fundamental quantities from meson-electroproduction data. This analysis also led to the determination of the long-awaited hadronic branching ratios for the D13(1520) decay into Delta pi (24%-32%) and N rho (8%-17%).