Electroproduction of p pi+ pi- off protons at 0.2 < Q**2 < 0.6-GeV**2 and 1.3 < W < 1.57-GeV with CLAS

This paper reports on the most comprehensive data set obtained on differential and fully integrated cross sections for the process ep. e -> p pi(+)pi(-). The data were collected with the CLAS detector at Jefferson Laboratory. Measurements were carried out in the as yet unexplored kinematic region of photon virtuality 0.2 < Q(2) < 0.6 GeV(2) and invariant mass of the final hadron system W from 1.3 to 1.57 GeV. For the first time, nine independent one-fold differential cross sections were determined in each bin of W and Q(2) covered by the measurements. A phenomenological analysis of the data allowed us to establish the most significant mechanisms contributing to the reaction. The nonresonant mechanisms account for a major part of cross sections. However, we find sensitivity to s-channel excitations of low-mass nucleon resonances, especially to the N(1440)P(11) and N(1520)D(13) states in kinematic dependencies of the one-fold differential cross sections.