Date of Award

Spring 2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

Program/Concentration

Physics

Committee Director

Stephen Bueltmann

Committee Member

Sebastian Kuhn

Committee Member

Raul Briceno

Committee Member

Yuan Zhang

Committee Member

Sylvain Marsillac

Abstract

Understanding the internal structure of nucleons is one of the primary goals of nuclear physicists. As protons and neutrons are only the bound state solution of the QCD lagrangian (at least inside atomic nuclei), studying protons and neutrons helps uncover nuclear structure. Due to its easy availability, many studies on protons have been done on a wide range of kinematics. However, free neutron targets are not readily achievable. So, any information on neutrons has to be extracted from neutron-rich nuclei, and some nuclear models have to be used to subtract the contributions from other nucleons to extract the information on neutrons. So, the Barely Off-shell Nucleon Structure (BONuS12) experiment at Jefferson Lab was conducted to overcome these challenges by using spectator tagging. The experiment effectively created a quasi-free neutron target by scattering electrons off a deuterium target and detecting low-momentum, backward-moving protons using a custom-built Radial Time Projection Chamber (RTPC). Selecting the low momentum and backward-moving spectators would enable us to minimize the model-dependent effects due to final state interactions and target fragmentation. The RTPC was a 40 cm-long cylindrical detector that worked on the principle of gaseous ionization. It had three layers of Gas Electron Multipliers (GEMs) for charge amplification and a surrounding readout pad. The scattered electrons were measured using the CLAS12 detector, and data were collected using a 10.4 GeV electron beam during Spring and Summer 2020. Using spectator tagging, we extracted the structure function ratio Fn2 of the quasi-free neutron in the deep inelastic scattering at high x, up to x ≈ 0.8. The result was extracted in the region with the invariant mass W > 1.8 GeV/c2 , and Q2 in the range 1.3 to 11 GeV2 . This dissertation presents the methodology, event selection criteria and refinements, estimation and subtraction of backgrounds, and complete analysis of the extraction of Fn2 /Fp2 in a model-independent way. Systematic uncertainties in our final analysis will also be discussed in detail.

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DOI

10.25777/fmm8-sj68

ISBN

9798280747067

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