Lambda(1520) measurements at the GlueX experiment

Pauli, Peter (2020) Lambda(1520) measurements at the GlueX experiment. PhD thesis, University of Glasgow.

Abstract

This thesis presents the first measurements of the photon beam asymmetry Sigma, spin-density matrix elements and differential cross-sections in Lambda(1520) photoproduction at photon beam energies between 8.2 GeV and 8.8 GeV. These measurements will help to constrain physics models, describing the production process of hadrons at high photon energies, as they are needed in the search for exotic mesons.
The data used in this analysis were recorded using the GlueX beamline and detector in Hall D of the Thomas Jefferson National Accelerator Facility (JLab) in Virginia, USA. JLab provides a 12 GeV electron beam which is converted to a linearly polarised photon beam on a thin diamond, via the coherent bremsstrahlung technique. The photon beam is incident on a liquid hydrogen target where it can produce various meson and baryon resonances such as the Lambda(1520). The GlueX detector setup surrounding the target is able to detect both charged and neutral final state particles resulting from the reaction. Careful analysis of their momentum and angular distributions allows the determination of the observables presented in this work.
For the extraction of physics observables the sPlot method was used together with unbinned extended maximum likelihood fitting and Markov Chain Monte Carlo methods. The effect of longitudinal phase space analyses was studied and resulted in a publication.
So far, previous measurements for this reaction have only been made at much lower or higher energies. This is the first measurement of this reaction in the energy range of GlueX. This work also provides the first measurement of polarised spin-density matrix elements for this reaction channel. These are critical steps towards GlueX’s main goal, which is to establish and map out the spectrum of exotic hybrid mesons, an important milestone in our understanding of quantum chromo dynamics and the strong force.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Appendix E contains published work
• Keywords: photoproduction, beam asymmetry, spin-density matrix elements, differential cross-section, Markov Chain Monte Carlo
• Subjects: Q Science > QC Physics
• Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
• Supervisor's Name: Ireland, Professor David
• Date of Award: 2020
• Depositing User: Peter Pauli
• Unique ID: glathesis:2020-81591
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 20 Aug 2020 07:29
• Last Modified: 14 Sep 2022 14:21
• Thesis DOI: 10.5525/gla.thesis.81591
• URI: https://theses.gla.ac.uk/id/eprint/81591