Development of the Tagger Microscope and Analysis of Spin Density Matrix Elements in (Photon, Proton) to (Phi, Proton) for the GlueX Experiment

Publication Year:
2017
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Repository URL:
https://opencommons.uconn.edu/dissertations/1413
Author(s):
Barnes, Alexander E
artifact description
The quark model has been successful in classifying the spectrum of mesons observed since the 1960s, however, it fails to explain some of the measured bound states. Lattice QCD predictions have shown that an excited gluonic field may contribute to the quantum numbers of the bound state and form hybrid mesons, qq-bar, where g is a constituent gluon. It is possible for some hybrids to possess quantum numbers forbidden by the quark model and are known as "smoking gun" hybrids due to their lack of mixing with conventional qq-bar states. The GlueX photoproduction experiment at Jefferson Lab in Newport News, VA is designed to study hybrid mesons and to map their spectrum. A 12 GeV electron beam produces 9 GeV linearly polarized photons via coherent bremsstrahlung in a diamond radiator which are incident on a liquid hydrogen target. In order to determine the photon energy, the use of a tagging spectrometer which measures the energy of the post-bremsstrahlung electron is required. The tagger microscope is a scintillating fiber detector designed to measure the energy of electrons corresponding to the polarized photons. The main focus of this work is the design and construction of the tagger microscope electronics as well as the calibration of the microscope within the experiment. Additionally, the analysis of the reaction (photon, proton) to (phi, proton), where the phi(1020) meson decays into K+K-, is discussed. This analysis provides a high-level calibration for GlueX in regards to understanding the acceptance and sensitivity of the detectors to mesons with strange quark content. By studying the phi with linearly polarized photons, information on the production mechanism can be extracted. The measurement of the phi meson spin-density matrix elements are shown and compared with past data which are found to be in agreement.