Date of Award

Fall 11-16-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

First Advisor

Markus Wobisch

Abstract

This dissertation presents a comprehensive study of multi-jet cross-section ratios using proton-proton collision data collected by the ATLAS detector during Run 2 of the Large Hadron Collider (LHC) at a center-of-mass energy of √ s = 13TeV. By examining these ratios across different energy scales, the analysis provides valuable insights into the running of the strong coupling constant, αs, a fundamental parameter in Quantum Chromodynamics (QCD) that dictates the strength of the strong interaction. The running of αs—its variation with energy—is crucial for understanding QCD, yet it remains one of the least precisely known aspects of the theory. In this study, multi-jet cross-section ratios serve as sensitive proxies for extracting αs, offering a robust method for probing its energy dependence. One notable advantage of this technique is the reduction or cancellation of systematic uncertainties, achieved by using cross-section ratios, which enhances the precision of the results. This results of this work provides the basis for future extractions of αs. The results are compared to predictions of different theoretical models, demonstrating a high degree of consistency between the measured data and the theoretical models, affirming the reliability of both the experimental approach and the underlying QCD theory.

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