Electro- and photoproduction of baryons and possible hybrid states at large momentum transfer

• Applicants: Professor Dr. Amand Fäßler; Professor Thomas Gutsche, Ph.D.
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: from 2014 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 265940448

• Final Report Year: 2023

Final Report Abstract

The project aimed for a comprehensive study of the nucleon and nucleon resonances in the light-front quark model motived by QCD. Baryon structure in this approach is based on the idea of mixing of the three-quark core component and the meson-baryon molecular component. This hypothesis was approved by data on the electrocoupling of nucleon resonances measured by the CLAS Collaboration at JLab (Newport News, USA). For the first time we sufficiently improved the description of the helicity amlitudes responsible for the exicitation of the Roper resonance. The predictions for the electrocouplings of other nucleon resonances have been made. Two main objectives obtained within present Research Proposal are formulated as: 1. We made a comprehensive study of electroproduction of low-lying nucleon resonances (Roper N1/2+ (1440), N1/2− (1535), etc.). 2. We studied the role of a hadronic molecular component in structure of nucleon resonances. In future one could extend our theoretical formalism to study baryon hybrids — exotic states with quantum numbers of baryons, which are composed of quarks and gluons. This topic is important in connection with the experimental program of the CLAS12 Collaboration at JLab (USA), where the spectroscopy and electrocoupling of baryon hybrids is under extensive study.

Publications

• Transition form factors and helicity amplitudes for electroexcitation of negative and positive parity nucleon resonances in a light-front quark model. Physical Review D, 100(9).
  Obukhovsky, Igor T.; Faessler, Amand; Fedorov, Dimitry K.; Gutsche, Thomas & Lyubovitskij, Valery E.