Excited Baryon Structure Using Exclusive Reactions with CLAS12

TL;DR

This paper discusses the study of excited nucleon structures via exclusive reactions with CLAS12, aiming to measure transition form factors for $N^*$ states up to 3 GeV in energy and 12 GeV$^2$ in momentum transfer.

Contribution

It introduces a program to analyze excited $N^*$ decays into various final states using CLAS12, expanding the exploration of nucleon excitations at higher energies and momentum transfers.

Findings

Determined electrocouplings for $N^*$ states below 1.8 GeV.

Highlighted the importance of analyzing multiple channels for consistency.

Proposed measurements of differential cross sections up to $W$=3 GeV and $Q^2$=12 GeV$^2$.

Abstract

Studying excited nucleon structure through exclusive electroproduction reactions is an important avenue for exploring the nature of the non-perturbative strong interaction. Electrocouplings for $N^*$ states in the mass range below 1.8~GeV have been determined from analyses of CLAS $\pi N$, $\eta N$, and $\pi \pi N$ data. This work made it clear that consistency of independent analyses of exclusive channels with different couplings and non-resonant backgrounds but the same $N^*$ electro-excitation amplitudes, is essential to have confidence in the extracted results. In terms of hadronic coupling, many high-lying $N^*$ states preferentially decay through the $\pi \pi N$ channel instead of $\pi N$. Data from the $KY$ channels will therefore be critical to provide an independent analysis to compare the extracted electrocouplings for the high-lying $N^*$ states against those determined from the $\pi N$ and $\pi \pi N$ channels. A program to study excited $N^*$ decays to non-strange and strange exclusive final states using CLAS12 will measure differential cross sections to be used as input to extract the $\gamma_vNN^*$ transition form factors for the most prominent $N^*$ states in the range of invariant energy $W$ up 3~GeV in the virtually unexplored domain of momentum transfers $Q^2$ up to 12~GeV$^2$.