Kaicheng Li

Kaicheng Li

Ph.D. 2023
Physics

Current Position: Machine Learning Engineer

Current Institution: Uber Technologies, Inc.

Advisor: Bonnie Flemming 

Degree Year: 2023

Thesis Title: Low Energy Excess and Anomaly Search with MicroBooNE

Thesis Abstract: The Micro Booster Neutrino Experiment (MicroBooNE) is a leading large-scale Liquid Argon Time Projection Chamber (LArTPC) experiment, designed for precision neutrino physics. The main scientific objectives of MicroBooNE include the investigation of the Low Energy Excess (LEE) observed by the MiniBooNE Experiment between 2002-2019 in the Booster Neutrino Beam (BNB) at Fermilab, the measurements of neutrino-argon interactions, and the research and development of LArTPC technology. This thesis focuses on understanding the MiniBooNE LEE through charged-current electron neutrino interactions. MicroBooNE BNB data, collected between February 2016 and July 2018, is analyzed for an electron-like low energy excess (eLEE) using Wire-Cell reconstruction. Enabled by human and machine-learning based selections, as well as novel statistical methods to limit modeling uncertainties, the Wire-Cell eLEE analysis disfavors the nominal eLEE hypothesis at 3.75σ significance with a simple vs. simple likelihood ratio test. Based on a nested likelihood ratio test guided by the Feldmans-Cousins procedure, the lower confidence bounds of MiniBooNE LEE are disfavored at 2.6σ, assuming statistical-only uncertainties, and at 3σ, assuming statistical and systematic uncertainties. A 3+1 active-sterile neutrino oscillation search is formulated, utilizing MicroBooNE data collected from both BNB and Neutrinos at the Main Injector (NuMI). BNB-only results exclude some allowed phase space by existing neutrino anomalies. Given different mixtures of intrinsic νe and intrinsic νμ , the combination of BNB and NuMI is expected to improve sensitivity, by resolving the cancellation effects between νe appearance and disappearance. Ongoing improvements for the NuMI flux prediction at MicroBooNE will also be an important piece to realize the optimal sensitivity in the combined BNB+NuMI search.

Information updated 07/18/2025

Experiments

MicroBooNE

Fleming

Science Goal: MicroBooNE is a short baseline accelerator neutrino oscillation experiment at Fermilab designed to investigate the source of the low energy excess observed by the MiniBooNE experiment, perform a unique set of low energy neutrino cross section measurements, and conduct R&D towards development of massive LArTPC detectors. 

WL involvement: Yale’s roles included fabrication and assembly of the TPC and DAQ systems, development of the analysis techniques and tools necessary to analyze the data, and oversight of the collaboration.

Group of people infront of part of MicroBooNE at Wright Lab.

News

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