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

[Daniel Carman]

Izzy,

I looked over your slides and things look quite good. A couple of comments from my side:

1) You should say that the electron beam was longitudinally polarized.

2) The systematic uncertainties are shown but you have not given any indication of what
sources contribute to this uncertainty. Could you include a table with the major contributions?

3) In your description of CLAS12, you have not said anything about the Moller polarimeter
system in Hall B. Perhaps that should be explicitly stated.

4) You might note that the Dec. 2018 RG-K run was just a short “opportunistic” run that
amounted to only ~10% of the approved RG-K beam time. This is important to note given the
current statistical limitations (which lead to larger bin sizes) of your data analysis.

5) You could mention on your final summary slide what the next steps in your analysis are
and plans for publication.

Regards,
Daniel

On May 15, 2024, at 1:28 PM, Izzy Illari via Clas_hadron <clas_hadron at jlab.org<mailto:clas_hadron at jlab.org>> wrote:

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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* Dr. Daniel S. Carman                  e-mail : carman at jlab.org<mailto:carman at jlab.org>
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* Jefferson Laboratory                web: http://userweb.jlab.org/~carman
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