Searching for new physics with Fermilab’s proton beam

Forbes, Diana Michelle

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https://hdl.handle.net/2142/129814 Copy

Description

Title

Searching for new physics with Fermilab’s proton beam

Author(s)

Forbes, Diana Michelle

Issue Date

2025-05-19

Director of Research (if dissertation) or Advisor (if thesis)

Kahn, Yonatan

Doctoral Committee Chair(s)

Shelton, Jessie

Committee Member(s)

• Gollin, George
• Witek, Helvi

Department of Study

Physics

Discipline

Physics

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• high energy
• phenomenology

Abstract

In this thesis, I summarize my work on two projects that use Fermilab's proton beam to search for new physics. The first project was in response to the anomalous muon magnetic moment announcement in 2021~\cite{Muong-2:2021ojo}. This project proposed that we can use the SpinQuest experiment \cite{apyan2022darkquestdarksectorupgrade}, with no additional installations needed, to look for a muonphillic scalar particle $S$ whose coupling to muons could resolve the anomalous muon magnetic moment. In this setup, a ${\sim}$100 GeV proton beam would travel through a thick target material to produce a muon beam through scattering off of the target nuclei. This muon beam would then traverse the last length of the target, estimated to be $\sim 100$ cm of material, to radiatively produce hypothetical scalar particles that would promptly decay into a muon pair. Hence, the signature would be an event with a pair of muons that has an invariant mass equal to the mass of the scalar particle. We simulated events for a choice of $3\times 10^{14}$ muons on target (MOT) with typical energies of $\sim$ 20 GeV, and, with a $15\%$ invariant mass resolution, this strategy can probe the entire parameter space for which $\sim$ 200 MeV -- GeV scalar particles resolve the muon $g-2$ anomaly. Ultimately, we estimated that we would only need about 6 years of beam time to achieve a $3 \sigma$ discovery sensitivity. For the second project, I collaborated with a group member named Rachel Nguyen to estimate the sensitivity of Fermilab's DUNE Near Detector site to detecting millicharged particles (MCPs) as well as heavy axion-like particles (ALPs). The majority of my work for this project focused on the MCP search. Regarding the MCP search, we utilized the setup of a proposed project named FerMINI \cite{Kelly:2018brz} to look for a MCP would be generated from charged pion scattering- a production channel that has been so far overlooked. We would use the DUNE Near Detector complex at Fermilab, with the additional installation of scintillator arrays and photomultiplier tubes (PMTs), to detect MCPs through soft ionizations. Fermilab's proton beam would pass through a graphite target, producing charged pions that secondarily scatter in the target to produce a $\chi \bar{\chi}$ pair from a virtual photon. The signature for detecting a MCP would be three soft ionizations through the scintillator arrays that are collinear with the beam line and target, detectable through the collection of photoelectrons by PMTs. Using the framework of chiral perturbation theory, we found a small region of parameter space, around $1.5 < m_\chi < 2.8$ GeV, where the charged pion production channel dominates over previously-considered production mechanisms. Regarding the ALP search, we proposed a search strategy that would use the DUNE Near Detector complex and charged pions to detect heavy axion-like particles (ALPs) with low-energy couplings to gluons. Again, using the framework of chiral perturbation theory, we demonstrated regimes of parameter space where the charged pion production channel dominates over previously-considered production mechanisms for ALPs, thereby improving the sensitivity of DUNE to these new particles compared to previous studies.

Graduation Semester

2025-08

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/129814

Copyright and License Information

2024 by Diana Forbes. All rights reserved

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