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 $e p \to e' p \pi^{+} \pi^{-} $. The data were collected with the CLAS detector at Jefferson Laboratory. Measurements were carried out in the so-far 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 1-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 non-resonant 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 kinematical dependencies of the 1-fold differential cross-sections. 
G.V.Fedotov, V.I.Mokeev, V.D.Burkert, L.Elouadrhiri, E.N.Golovatch,   B.S.Ishkhanov, E.L.Isupov, N.V.Shvedunov (for the CLAS...