The Nucleon Resonance Structure from the π+π−p Electroproduction Reaction off Protons

Abstract

The data on photo- and electroexcitation amplitudes of most nucleon resonances in the mass range up to 2.0 GeV determined from the CLAS experiments on exclusive π⁺π⁻p photo-electroproduction off protons in collaboration between the Jefferson Lab and Moscow State University are presented. The first (and, currently, the only available) data on electroexcitation amplitudes from CLAS in a wide range of photon virtualities Q² <5.0 GeV² reveal the nucleon resonance structure as a complex interplay between the inner core of three dressed quarks and an external meson-baryon cloud. These results shed light on the strong QCD dynamics, which underlies the generation of excited nucleon states with different structural features from confined quarks and gluons. The future prospects of these studies in the new era of experiments with the CLAS 12 detector, which began in the spring of 2018, are outlined.