The search for strangeonium resonances: partial wave analysis of polarised photoproduction reaction γp → ηφp at the GlueX experiment

Darulis, Darius (2026) The search for strangeonium resonances: partial wave analysis of polarised photoproduction reaction γp → ηφp at the GlueX experiment. PhD thesis, University of Glasgow.

Abstract

The strong force gives rise to a large hadron spectrum, many areas of which are still not well understood. Progress in mapping out these regions is vital for building better models of the strong force and verifying the predictions of its quantum field theory, Quantum Chromodynamics. This thesis focuses on the study of the so-called strangeonium states, which are mesons with s¯s quark content, and in particular on members of the φ meson series φ(1680) and φ3(1850). The former is a radially excited vector that has been seen by both e⁺e⁻ collider and photoproduction experiments, but whose reported mass does not match between the two, with observations from photoproduction being systematically higher; the latter is a tensor that has not been measured since the 1980s and never in experiments with high statistical power.

The data analysed in this thesis was collected at the GlueX experiment, which has produced the world’s largest photoproduction dataset to date since starting to run in 2016. A 9 GeV linearly polarised photon beam incident on a liquid hydrogen target was used to produce a variety of mesonic and baryonic resonances. The GlueX spectrometer allows both neutral and charged final states to be exclusively reconstructed with good resolution and angular acceptance. Results from the partial wave analysis of decay channel γp→ηφ p→K⁺K⁻γγ p are presented.

After signal was isolated from background using a combination of event selection criteria and statistical subtraction via the sPlot method, an extended maximum likelihood fit to angular decay distributions allowed the extraction of partial wave amplitudes. A partial wave consistent with the φ(1680) was observed, but no clear evidence of a φ3(1850) was found. The obtained amplitudes indicated a preference for natural parity exchange. A fit to the intensity of the wave identified as the φ(1680) resulted in a Breit-Wigner mass more compatible with the e⁺e⁻ measurements. A cross-section was also calculated, allowing an order-of-magnitude estimate that matched the existing predictions.

The results provide evidence against the additional vector meson states that have been previously hypothesised to explain the higher observed mass of the φ(1680) in photoproduction. They should also aid the development of models of the strangeonium spectrum.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QC Physics
• Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
• Supervisor's Name: Ireland, Professor David and Hurck, Dr. Peter
• Date of Award: 2026
• Depositing User: Theses Team
• Unique ID: glathesis:2026-85692
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 16 Jan 2026 11:00
• Last Modified: 16 Jan 2026 11:03
• Thesis DOI: 10.5525/gla.thesis.85692
• URI: https://theses.gla.ac.uk/id/eprint/85692