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The analysis of the nine 1-fold differential cross sections for the $gamma_{r,v} p to pi^+pi^-p$ photo- and electroproduction reactions obtained with the CLAS detector at Jefferson Laboratory was carried out with the goal to establish the contributing resonances in the mass range from 1.6~GeV to 1.8~GeV. In order to describe the photo- and electroproduction data with $Q^2$-independent resonance masses and hadronic decay widths in the $Q^2$ range below 1.5~GeV$^2$, it was found that an $N(1720)3/2^+$ state is required in addition to the already well-established nucleon resonances. This work demonstrates that the combined studies of $pi^+pi^-p$ photo- and electroproduction data are vital for the observation of this resonance. The contributions from the $N(1720)3/2^+$ state and the already established $N(1720)3/2^+$ state with a mass of 1.745~GeV are well separated by their different hadronic decays to the $pi Delta$ and $rho p$ final states and the different $Q^2$-evolution of their photo-/electroexcitation amplitudes. The $N(1720)3/2^+$ state is the first recently established baryon resonance for which the results on the $Q^2$-evolution of the photo-/electrocouplings have become available. These results are important for the exploration of the nature of the ``missing baryon resonances.
The results on the photo- and electroexcitation amplitudes of most nucleon resonances in the mass range up to 2.0 GeV determined from the CLAS experimental data on exclusive $pi^+pi^-p$ photo-/electroproduction off protons in collaboration between th
The transition helicity amplitudes from the proton ground state to the $N(1440)1/2^+$, $N(1520)3/2^-$, and $Delta(1620)1/2^-$ resonances ($gamma_vpN^*$ electrocouplings) were determined from the analysis of nine independent one-fold differential $pi^
The transition gamma_{v}pN^* amplitudes (electrocouplings) for prominent excited nucleon states obtained in a wide area of photon virtualities offer valuable information for the exploration of the N^* structure at different distances and allow us to
Studies of the nucleon resonance electroexcitation amplitudes in a wide range of photon virtualities offer unique information on many facets of strong QCD behind the generation of all prominent excited nucleon states. Advances in the evaluation of re
Exclusive neutral-pion electroproduction ($epto e^prime p^prime pi^0$) was measured at Jefferson Lab with a 5.75-GeV electron beam and the CLAS detector. Differential cross sections $d^4sigma/dtdQ^2dx_Bdphi_pi$ and structure functions $sigma_T+epsilo