Experimental and Phenomenological Investigations of the MiniBooNE Anomaly
This thesis covers a range of experimental and theoretical efforts to elucidate the origin of the $$4.8\sigma$$ MiniBooNE low energy excess (LEE). We begin with the follow-up MicroBooNE experiment, which took data along the BNB from 2016 to 2021. This thesis specifically presents MicroBooNE's search for $$\nu_e$$ charged-current quasi-elastic (CCQE) interactions consistent with two-body scattering. The two-body CCQE analysis uses a novel reconstruction process, including a number of deep-learning-based algorithms, to isolate a sample of $$\nu_e$$ CCQE interaction candidates with $$75\%$$ purity. The analysis rules out an entirely $$\nu_e$$-based explanation of the MiniBooNE excess at the $$2.4\sigma$$ confidence level. We next perform a combined fit of MicroBooNE and MiniBooNE data to the popular $3+1$ model; even after the MicroBooNE results, allowed regions in $$\Delta m^2$$-$$\sin^2 2_{\theta_{\mu e}}$$ parameter space exist at the $$3\sigma$$ confidence level. This thesis also demonstrates that the MicroBooNE data are consistent with a $$\overline{\nu}_e$$-based explanation of the MiniBooNE LEE at the $$<2\sigma$$ confidence level. Next, we investigate a phenomenological explanation of the MiniBooNE excess combining the $3+1$ model with a dipole-coupled heavy neutral lepton (HNL). It is shown that a 500 MeV HNL can accommodate the energy and angular distributions of the LEE at the $$2\sigma$$ confidence level while avoiding stringent constraints derived from MINER$$\nu$$A elastic scattering data. Finally, we discuss the Coherent CAPTAIN-Mills experiment--a 10-ton light-based liquid argon detector at Los Alamos National Laboratory. The background rejection achieved from a novel Cherenkov-based reconstruction algorithm will enable world-leading sensitivity to a number of beyond-the-Standard Model physics scenarios, including dipole-coupled HNLs.
- Research Organization:
- Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 1997540
- Report Number(s):
- FERMILAB-THESIS-2023-07; arXiv:2308.12015; oai:inspirehep.net:2690438
- Country of Publication:
- United States
- Language:
- English
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