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GlueX Experiment Document 4172-v1

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Development of the Barrel Calorimeter Reconstruction and Measurement of the Beam Asymmetry ($\Sigma$) for Photoproduced $\pi^0$ and $\eta$ Mesons with the GlueX Experiment

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Will McGinley
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Will McGinley
Document Created:
19 Sep 2019, 15:19
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19 Sep 2019, 15:19
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19 Sep 2019, 15:19
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The GlueX experiment is located in Hall D at Jefferson Lab with the primary goal of mapping out the spectrum of hybrid mesons. GlueX features a nearly-4$\pi$ hermetic detector capable of measuring neutral and charged particles produced by a 9 GeV linearly polarized photon beam incident on a liquid hydrogen target. A description of the detector is presented to give an overview of the experiment. A lot of effort has been put forth into analyzing the data recorded by the detector. Here I discuss improving the performance of the Barrel Calorimeter subdetector by calibrating the gains and improving the reconstruction software. The immediate physics goal of GlueX is to measure observables of known particles, especially those that are expected to be decay particles of hybrid mesons, such as $\pi^0$ and $\eta$. To understand the photoproduction mechanism of these two particles the beam asymmetry ($\Sigma$) observable is measured. The measurements of $\Sigma$ are obtained as a function of the four-momentum transfer squared, -t, in the photon energy range of 8.2 GeV to 8.8 GeV in the three dominant decay modes of the $\eta$ meson and in the dominant decay mode of the $\pi^0$ meson. These are the first results for the $\eta$ meson at this beam energy in multiple decay modes. The results agree with previously published GlueX results for $\eta$ and $\pi^0$ and are made with significantly higher statistical precision. There is also agreement between theory predictions and the results which indicates that the resonance production mechanisms of the $\pi^0$ and $\eta$ mesons are dominated by natural parity exchange.
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