[Clas_hadron] Slides and abstract for ATHOS at William & Mary

[Izzy Illari]

Dear HSWG members,

I am planning to present beam spin asymmetry results using RGK at the 
upcoming ATHOS conference from May 28 - June 1, 2024. Justin approached 
RGK group and Annalisa for talks. The slides and abstract for this 
presentation are attached for your review.

These results were previously shown internally at the March CLAS 
Collaboration meeting. As per Bryan's advice, I am circulating the 
slides and abstract to the HSWG to receive comments and suggestions 
before proceeding with the presentation.

Please note that all plots containing CLAS12/RGK data have been marked 
as "preliminary."

I would appreciate any feedback or suggestions you may have regarding 
the content of the presentation.

All the best,

Izzy

Exclusive $\eta$ Electro-Production Beam Spin Asymmetry Measurements 
using CLAS12 at Jefferson Lab

The exploration of nucleon structure and electromagnetic transitions 
from ground state to excited state is a cornerstone of nuclear physics 
research. Meson electro-production experiments have opened new avenues 
for investigating these phenomena, particularly in the 12 GeV era at 
Jefferson Lab with the CLAS12 spectrometer. The $\eta N$ final states, 
accessible only through isospin $I = 1/2$ resonances, provide a unique 
tool for studying nucleon excitations. By simplifying the analysis and 
enabling a cleaner extraction of resonance properties compared to the 
extensively studied $\pi N$ final states, $\eta$ electro-production 
offers a complementary approach to unraveling the structure of excited 
nucleons. This work presents the first-ever measurement of the beam spin 
asymmetry (BSA) in exclusive $\eta$ electro-production, covering a 
previously unexplored kinematic region with $1.6 \leq W \leq 2.2$ GeV. 
The BSA is extracted from the CLAS12 data using a comprehensive analysis 
framework that carefully considers the statistical limitations of the 
data set. The results are compared to predictions from theoretical 
models, such as the J"{u}lich-Bonn-Washington (JBW) and MAID, as well as 
compared to previously published cross-section and spin observable 
results from CLAS, and SLAC. Notably, the extracted BSA exhibits 
discrepancies with the model predictions, highlighting the potential for 
refining theoretical descriptions of nucleon resonances and their 
electromagnetic couplings through the incorporation of these new data. 
The high-precision data obtained in this previously unmeasured kinematic 
region now serve as valuable input for theorists to refine their models.
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