Search for Higgs Portal Scalars and Heavy Neutral Leptons Decaying in the MicroBooNE Detector
- Manchester U.
This thesis presents a search for Higgs Portal Scalars (HPS) and Heavy Neutral Leptons (HNL) decaying in the MicroBooNE liquid argon time projection chamber (LArTPC). The measurement was performed using data collected in-time with the Neutrino at the Main Injector (NuMI) beam with a total exposure corresponding to $$7.01 \times 10^{20}$$ protons on target. Mono-energetic HPS and HNL would be produced from kaons decaying at rest in the NuMI hadron absorber, before travelling $${\sim}100$$~m to the MicroBooNE detector where they decay. A single selection and search strategy is used to target decays of HPS to $$\mu\mu$$ pairs and HNL to $$\mu\pi$$ pairs. The results are expressed as limits, at the $$90\%$$ confidence level, on the mixing angles that control the rates of production and decay for each new particle. For the HNL model, upper limits are set on the mixing parameter $$\mumix$$ in the range [$$12.9 \times 10^{-8}$$, $$0.54 \times 10^{-8}$$] for HNL with masses in the region $246$--$385$~MeV. % This represents an order of magnitude increase in sensitivity to the previous MicroBooNE HNL result. For the HPS model, limits on the scalar-Higgs mixing angle $$\theta^2$$ are set, excluding a region with a lower boundary between [$$31.3 \times10^{-9}$$, $$1.09 \times 10^{-9}$$] and an upper boundary between [$$2.50 \times 10^{-5}$$, $$5.05 \times 10^{-9}$$] for scalars with a mass of $212$--$275$ MeV. These results set the first constraints in this region of parameter space from a dedicated experimental search for HPS.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 1867643
- Report Number(s):
- FERMILAB-THESIS-2022-05; oai:inspirehep.net:2081533
- Country of Publication:
- United States
- Language:
- English
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