Status of the PrimEx‑eta radiative decay width experiment in Hall D at Jefferson Lab*

The first run of a new experiment, PrimEx-eta (E12-10-011), was carried out in Hall D at Jefferson Lab using the GlueX experimental setup. Its goal is to precisely extract the η→γγ radiative decay width from the photoproduction of η‑mesons at extreme forward angles using the so-called Primakoff effect. The two-photon decay of the η‑meson proceeds predominantly due to Chiral anomaly in QCD. The projected 3.2% accuracy of the η decay width measurement will significantly impact the η-sector of the Particle Data Group’s (PDG) compilation, sizably improving the average value on Γ(η→γγ) and significantly improving the rest of the η partial decay widths which, in turn, will positively impact the extraction of the light quark mass ratio and the η—η′ mixing angle. The first run of this experiment was completed in the spring of 2019 to test the capability of the experimental setup and also yielded a rich and good statistics initial experimental data set. The second run of the experiment will take place from August to October 2021. We are currently analyzing the data to check the experimental method and to prepare for the second run. Preliminary physics distributions will be presented and discussed in this talk as well as discussing the status of the second run that will have just concluded.