Date of Award

Winter 2020

Project Type

Dissertation

Program or Major

Physics

Degree Name

Doctor of Philosophy

First Advisor

Maurik Holtrop

Second Advisor

Mark L McConnell

Third Advisor

Karsten Pohl

Abstract

The Heavy Photon Search (HPS) experiment is based out of the Thomas Jefferson National Accelerator Laboratory in Newport News and is designed to test the potential existence of a new particle, the "heavy photon" or "A'," which has the potential to mediate interactions between dark forces and the Standard Model. HPS is designed to detect the decay of an A' particle into e⁺e⁻ pairs utilizing an electromagnetic calorimeter and a silicon-strip tracking detector. If the theory is correct, the A' could be generated using the Jefferson Lab high-luminosity electron beam incident upon a tungsten target.

In 2016, HPS collected 10.6 pb⁻¹ of data and searched for signs of the A' using a resonance search analysis to search for excesses in the invariant mass spectrum of e⁺e⁻ pairs across a mass range of 39 MeV to 180 MeV. HPS finds no statistically signiffcant excess in the invariant mass spectrum and establishes an upper limit to the coupling constant ε² within the search mass range.

The history and motivations for the A' are discussed. The HPS apparatus is motivated and described, and the software used to emulate it and to verify its behavior is discussed. Lastly, the resonance search is discussed, including the selection of e⁺e⁻ pairs, the parameterization of the mass resolution and radiative fraction, the methodology behind the resonance search, and the final search results.

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