ИСТИНА

Studies of genuinely nonperturbative nucleon resonance (N*) structure via exclusive electroproduction off nucleons offer critical insights into the origin of the dominant component of hadron mass—one of the most fundamental open problems in subnuclear physics [1]. This talk will present results from N* electroexcitation with the CLAS detector and outline future directions using data from ongoing experiments with the upgraded CLAS12 detector in Hall B at Jefferson Lab. Exclusive π⁰p, π⁺n, and π⁺π⁻p electroproduction measurements with CLAS have yielded the only available results worldwide for helicity transition amplitudes of most nucleon resonances with masses below 1.8 GeV and photon virtualities up to Q² = 5.0 GeV².These findings reveal a complex internal structure of N* states, involving both a dressed-quark core and an external meson-baryon cloud [2]. Independent analyses of pion form factors, nucleon elastic form factors, and the electroexcitation amplitudes of Δ(1232)3/2⁺, N(1440)1/2⁺, and Δ(1600)3/2⁺ resonances have produced consistent results for the dressed-quark mass function. These results demonstrate the capability to map its momentum dependence and gain direct insight into the emergence of hadron mass (EHM) from QCD. CLAS12 [3], the world's most capable facility for such studies, enables access to the high-Q² regime (Q² > 5.0 GeV²) where the transition from the strong to perturbative QCD is expected. This research will address key open questions about hadron mass generation, confinement, and their emergence from QCD, particularly in connection with dynamical chiral symmetry breaking [4]. 1. D.S. Carman, R.W. Gothe, V.I. Mokeev. and C.D. Roberts, Particles 6, 416 (2023). 2. Carman D.S., Joo K., Mokeev V.I. Few Body Syst. (2020) 61, 29. 1. 3. V.D. Burkert, L. Elouadrhiri, K.P. Adhikari et al. Nuclear Inst. and Methods in Physics Research, A 959, 163419 (2020). 4. Brodsky S.J. et al International Journal of Modern Physics E Vol. 29, No. 08, 2030006 (2020).