The GlueX Start Counter & Beam Asymmetry $\Sigma$ in Single $\pi^{0}$ Photoproduction

Authors

Eric J. Pooser, Florida International UniversityFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Physics

First Advisor's Name

Werner Boeglin

First Advisor's Committee Title

Committee member

Second Advisor's Name

Lei Guo

Second Advisor's Committee Title

Committee member

Third Advisor's Name

Misak Sargsian

Third Advisor's Committee Title

Committee member

Fourth Advisor's Name

Cem Karayalcin

Fourth Advisor's Committee Title

Committee member

Keywords

GlueX, Start Counter, Scintillator, SiPM, Beam Asymmetry, Photoproduction, Jefferson Lab, Hadron Spectroscopy, Instrumentation

Date of Defense

3-25-2016

Abstract

The GlueX experiment aims to study meson photoproduction while utilizing the coherent bremsstrahlung technique to produce a 9 GeV linearly polarized photon beam incident on a liquid $\mathrm{H_{2}}$ target. A Start Counter detector was fabricated to properly identify the accelerator electron beam buckets and to provide accurate timing information. The Start Counter detector was designed to operate at photon intensities of up to $\mathrm{10^{8}\gamma/s}$ in the coherent peak and provides a timing resolution $\mathrm{\sim 300\ ps}$ so as to provide successful identification of the electron beam buckets to within 99\% accuracy. Furthermore, the Start Counter detector provides excellent solid angle coverage, $\sim 90 \%\ \mathrm{of}\ 4 \pi\ \mathrm{hermeticity}$, and a high degree of segmentation for background rejection. It consists of a cylindrical array of 30 scintillators with pointed ends that bend towards the beam at the downstream end. Magnetic field insensitive silicon photomultiplier detectors were selected as the readout system.

An initial measurement of the beam asymmetry $\Sigma$ in the exclusive reaction $\vec{\gamma}p \rightarrow \pi^{0}p$, where $\pi^{0} \rightarrow \gamma \gamma$ has been carried out utilizing the GlueX spectrometer during the Spring 2015 commissioning run. The tagged photon energies ranged from $2.5 \leq E_{\gamma} \leq 3.0\ \mathrm{GeV}$ in the coherent peak. These measurements were then compared to the world data set and show remarkable agreement with only two hours of physics production running.

Identifier

FIDC000274

Recommended Citation

Pooser, Eric J., "The GlueX Start Counter & Beam Asymmetry $\Sigma$ in Single $\pi^{0}$ Photoproduction" (2016). FIU Electronic Theses and Dissertations. 2450.
https://digitalcommons.fiu.edu/etd/2450