New results from the studies of theN(1440)1/2+, N(1520)3/2−, andΔ(1620)1/2−resonances in exclusiveep→e′p′π+π−electroproduction with the CLAS detectorстатья
Статья опубликована в высокорейтинговом журнале
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Аннотация:The transition helicity amplitudes from the proton ground state to the N(1440)1/2+, N(1520)3/2−, and Δ(1620)1/2− resonances (γvpN∗ electrocouplings) were determined from the analysis of nine independent onefold differential π+π−p electroproduction cross sections off a proton target, taken with CLAS at photon virtualities 0.5GeV2<Q2<1.5 GeV2. The phenomenological reaction model employed for separation of the resonant and nonresonant contributions to this exclusive channel was further developed. The N(1440)1/2+, N(1520)3/2−, and Δ(1620)1/2− electrocouplings were obtained from the resonant amplitudes of charged double-pion electroproduction off the proton in the aforementioned area of photon virtualities for the first time. Consistent results on γvpN∗ electrocouplings available from independent analyses of several W intervals with different nonresonant contributions offer clear evidence for the reliable extraction of these fundamental quantities. These studies also improved the knowledge on hadronic branching ratios for the N(1440)1/2+, N(1520)3/2−, and Δ(1620)1/2− decays to the πΔ and ρN final states. These new results provide a substantial impact on the QCD-based approaches that describe the N∗ structure and demonstrate the capability to explore fundamental ingredients of the nonperturbative strong interaction that are behind the excited nucleon state formation.