Testing Explanations of Short Baseline Neutrino Anomalies

This thesis, encompassing both theory to experiment, guides the reader in a pedagogical way through the author’s attempts to resolve the mystery of the so-called MiniBooNE anomaly, where unexpected neutrino oscillations were reported, potentially explainable by the existence of light sterile neutrinos, but in contradiction with several null results. Within this context, this thesis reports one of the first analyses searching for an excess of electrons in the MicroBooNE experiment finding no excess of events and narrowing down the possible explanations for the anomaly. Additionally, this thesis explores non-minimal heavy neutral leptons as potential explanations for the MiniBooNE excess. To search for evidence for this particle, the author performs an analysis using data from the T2K experiment, which searched for pairs of electrons using a gas argon time projection. This thesis provides a comprehensive explanation of the MiniBooNE anomaly and test of its possibile explanation with liquid and gas time projection chambers.

Chapter 1: Prologue.- Part 1: Active and Sterile Neutrinos.- Chapter 2: Neutrinos within the Standard Model.- Chapter 3: Short baseline anomalies.- Chapter 4: Neutrinos beyond the Standard Model.- Part 2: Heavy Sterile Neutrino Explanations.- Chapter 5: Minimal and non-minimal models.- Chapter 6: Dark Neutrinos.- Part 3: Light Sterile Neutrino Explanations.- Chapter 7: The Micro Booster Neutrino Beam Experiment.- Chapter 8: Identifying neutrinos: tracks and showers.- Chapter 9: The quest for electron neutrinos.- Chapter 10: Interpreting the results.- Chapter 11: Epilogue.

Nicolò Foppiani is working for the NGO Officine Italia, that he co-founded in 2020 at the beginning of the COVID-19 pandemic, to increase youth participation in public policy and agenda setting. He graduated with a physics PhD at Harvard in 2022. His thesis work focused on neutrino physics and the search for sterile neutrinos. While a PhD student he was awarded the prestigious Goldhaber Prize by the Harvard physics department, recognizing outstanding graduate students in the middle of thr PhD programs.

He cultivated his interest for public speaking as a Harvard Horizons Scholar, delivering a presentation about his thesis work in front of a multidisciplinary audience, and winning the graduate student SLAM in 2020, a competition among graduate student to give the best three-minutes presentation at the APS April Meeting. He also cultivated a strong interest for building community, serving as graduate student liason in the Harvard Mountaineering club between 2019 and 2021 and as vice-president for the Harvard Italian Student Society in 2019.

He graduated with his Bachelor's and Master's in physics from Unviersity of Pisa. At the same time, he was a student at Scuola Normale Superiore, where he complemented and deepened his physics education. His interest for particle physics started in 2015, when we worked on simulations for the Future Circular Collider for his Bachelor’s thesis. He was selected as a Summer Student at CERN in 2016, and came back for his Master’s thesis on the “Measurement of the mass of the W boson with the CMS experiment”, which was later awarded the Tito Maiani prize in 2018 for the best thesis in particle physics.

He is now transitioning to more applied research, brancing out in the field of nuclear fusion, planning to contribute to the first realization of a nuclear fusion power plant, producing abdundant, clean, and safe energy shaping the post-fossil-fuels world.