Jun 2 – 7, 2019
Carnegie Mellon University
America/New_York timezone

## Excited Nucleon Spectrum and Structure Studies with CLAS and CLAS12

Jun 3, 2019, 1:30 PM
30m
Rangos 2

### Rangos 2

Invited Nucleon Structure

### Speaker

Daniel Carman (JLab)

### Description

The study of the spectrum and structure of excited nucleon states employing the electroproduction of exclusive reactions is an important avenue for exploring the nature of the non-perturbative strong interaction. The CLAS detector in Hall~B has provided the dominant part of the available world data on all relevant meson electroproduction channels off the nucleon in the resonance region for $Q^2$ up to 5~GeV$^2$. Analyses of CLAS data for the exclusive channels $\pi N$, $\eta N$, and $\pi \pi N$ on a proton target have provided the only results available on the $Q^2$ evolution of the helicity amplitudes for the transitions from the initial photon-proton to the final $N^*$ states in the mass range up to $W$=1.8~GeV. These electrocoupling amplitudes allow for exploration of the internal structure of the produced $N^*$ states. This work has made it clear that consistent results from independent analyses of several exclusive channels with different resonance hadronic decay parameters and non-resonant backgrounds but the same $N^*$ electro-excitation amplitudes, is essential to have confidence in the extracted results. Starting in early 2018, a program to study the spectrum and structure of $N^*$ states in various exclusive electroproduction channels using the new CLAS12 spectrometer commenced. These studies will probe the structure of these states in the mass range up to $W$=3~GeV and for $Q^2$ as low as 0.1~GeV$^2$ and as high as 10-12~GeV$^2$, thus providing a means to access $N^*$ structure information spanning a broad regime encompassing both low and high energy degrees of freedom. Quasi-real photoproduction studies are also planned to search for additional $N^*$ states, the so-called hybrid baryons, for which the glue serves as an active structural component. In this talk the $N^*$ programs from both CLAS and CLAS12 will be reviewed.

Early Consideration No No