Excited Baryon Structure Using Exclusive Reactions with CLAS12

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 $πN$, $ηN$, and $ππN$ 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 $ππN$ channel instead of $πN$. 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 $πN$ and $ππN$ 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 $γ_vNN^*$ 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$^2$.