The transition helicity amplitudes from the proton ground state to the P11(1440) and D13(1520) excited states (γvpN* electrocouplings) were determined from the analysis of nine independent one-fold differential π+π -p electroproduction cross sections off a proton target, taken with CLAS at photon virtualities of 0.25<Q2<0.60GeV2. The phenomenological reaction model was employed for separation of the resonant and nonresonant contributions to the final state. The P11(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 π+n and π0p channels. The successful description of a large body of data in dominant meson-electroproduction channels off protons with the same γvpN* 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 Δπ (24%-32%) and Nρ (8%-17%).
ASJC Scopus subject areas
- Nuclear and High Energy Physics