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Abstract:
The existence of three distinct neutrino flavors, with oscillations between them, has been established by several experiments over the past decades. However, anomalies observed in experiments such as LSND, MiniBooNE, and gallium source experiments have motivated the hypothesis of an additional neutrino state—a sterile neutrino—that does not interact directly with matter yet oscillates with the three known flavors (the 3+1 model). MicroBooNE was constructed, in part, to provide a definitive test of these anomalies. Located at Fermilab, MicroBooNE employs an 85-tonne active-mass liquid argon time projection chamber neutrino detector. It can distinguish between photon and electron electromagnetic showers and select charged-current electron neutrino and muon neutrino events with exceptional performance. In this talk, I will present our latest results from MicroBooNE search for an eV-scale sterile neutrino in the 3+1 model. This analysis uniquely combines data from two accelerator neutrino beams, the on-axis BNB beam and the off-axis NuMI beam, observed in MicroBooNE's single detector. This dual-beam approach helps break degeneracies between electron-neutrino appearance and disappearance, thereby extending our 95% confidence-level exclusion coverage to most of the parameter space suggested by the LSND, MiniBooNE, and gallium experiments. We find no evidence for sterile neutrino oscillations and, consequently, establish world-leading constraints on the 3+1 model from a single experiment.
About the speaker:
Xiangpan Ji is an Associate Professor and Ph.D. supervisor at the School of Physics, Nankai University. He earned his Ph.D. from Nankai University and subsequently conducted postdoctoral research at Tsinghua University and Brookhaven National Laboratory. He has worked on experimental neutrino physics for over ten years, contributing to the Daya Bay, PROSPECT, and MicroBooNE neutrino experiments. After returning to China in 2023, he joined Nankai University, where he participated in JUNO and JNE.
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