Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session Y07: Light Mesons and Baryons
1:30 PM–3:18 PM,
Tuesday, April 12, 2022
Room: Salon 4
Sponsoring Unit: GHP
Chair: Rosi Reed, Lehigh University
Abstract: Y07.00003 : The $\eta$-meson photoproduction off a helium nucleus and off quasi-free nucleons at GlueX.
1:54 PM–2:06 PM
for the GlueX Collaboration
off a helium nucleus. The produced $\eta$-meson can be reconstructed by detecting either $\eta \to 2\gamma$ or $\eta \to 3\pi$ decays. The particularly long distance between the target and the Forward Calorimeter gives rise to an irreducible background produced along the beam-line for the decay $\eta \to 2\gamma$
which is strongly suppressed or not present for the decays $\eta \to 3\pi$. Therefore, reconstructing $\eta$-meson from these two decay channels will help controlling the experimental systematics of
the differential cross-section measurement for the coherent $\eta$-meson photoproduction off the He target at very forward polar angles where the Primakoff peak is expected. In addition, a large
$\eta$-meson data sample from photoproduction off a helium nucleus and off quasi-free nucleons will allow a precision measurement of the $\eta \to 3\pi$ Dalitz distribution, which will improve
light-quark mass ratio determination and search for new CP violation beyond the standard model. The first run was performed with the GlueX experimental setup in Hall D in 2019 and the second run in
fall 2021 with the same setup but with the GlueX solenoid turn on. We will discuss the status of experiment and data analysis.
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