Date of Award

Summer 8-2023

Document Type


Degree Name

Doctor of Philosophy (PhD)




Nuclear & Particle Physics

Committee Director

Charles E. Hyde

Committee Member

Moskov Amaryan

Committee Member

Balša Terzić

Committee Member

Alexander Godunov

Committee Member

John Cooper


This experiment investigates the deep virtual production of both σ− and ρ− mesons, with a particular focus on the microscopic structure of the σ mesons. While the ρ meson is an ordinary qq¯ pair, the σ meson is composed of not only the typical qq¯ pair, making it a topic of controversy for nearly six decades. Although the existence of the σ− meson is now well established, its microscopic structure remains poorly understood. The primary objective of this thesis is to contribute to the understanding of the σ meson by analyzing its deep virtual production. The main focus of this study was on the ep → e ′p ′π +π − reaction, which is a crucial process for investigating both the σ− and ρ− mesons. Specifically, this reaction is sensitive to the pure glue component of the σ− meson’s wave function near the threshold in the ππ− system. In order to separate the σ− and ρ− meson channels, we analyzed the angular distribution in the ππ rest frame. By focusing on this reaction and employing this technique, we aimed to gain a better understanding of the structure of both the σ− and ρ− mesons. The model has developed according to Lehmann-Dronke to understand the σ− and ρ− mesons separately. To conduct our experiment, we chose to use the data from the Hall B CLAS12 “Run Group A” with an electron beam energy of 10.6 GeV incident on the LH2 target. The CLAS12 detector in Hall B has a large acceptance, making it an ideal choice for our study. By using this data, we were able to obtain accurate and reliable measurements of the ep → e ′p ′π +π − reaction and further our understanding of the σ− and ρ− mesons.


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