Baryon Transition Form Factors from Dynamical Coupled-Channel Analyses

Abstract

In this talk, the electromagnetic transition form factors from the nucleon ground state to twelve $N^*$ and $Δ$ states are exhibited and discussed. Those results are extracted through a comprehensive coupled-channel approach -- the Juelich-Bonn-Washington model, with the center-of-mass energy ranging from $1.13$ GeV to $1.8$ GeV, and the photon virtuality up to $8$ GeV$^2$. The extraction is based on $10^5$ electroproduction data points of $πN$, $ηN$, and $KΛ$ channels, with additionally about $5\times 10^4$ data points in the hadronic sector as well as photoproductions as boundary conditions. The form factors are defined from the residues at the corresponding resonance poles in the multipole amplitudes. Uncertainties are also estimated by the exploration of the parameter space. The qualitative behavior of the transition form factors of $N(1440)$ and $Δ(1232)$ here are in agreement with the previous studies, while for the other states, there has not been literature results that are also defined at the resonance poles.

Figures (2)

• Figure 1: The TFFs of the $N^*$ (left and middle panels) and $\Delta$ (right panel) states. The horizontal axis labels $Q^2/{\rm GeV}^2$. In each panel, the three figures from the left to the right shows $A_{1/2}$, $A_{3/2}$, and $S_{1/2}$, respectively. The bands represent the uncertainties stemming from the analyses in Ref. Mai:2023cbp. Literature results from MAID Tiator:2016btt and ANL-Osaka Kamano:2018sfb are depicted by empty symbols.
• Figure 2: The amplified plot of the TFFs of $N(1440)$ in the small-$Q^2$ region (left), and the transverse transition charge distributions of $N(1440)$ (right). For the figure on the right: the inset shows corresponding coordinate decompositions with light/dark shades representing negative/positive values; the orange band (thick red line) depicts the result of $\rho_0^{pN^*}$ shown in this talk (from the MAID 2007 solution Drechsel:2007if).