MicroBooNE

MicroBooNE. The MicroBooNE experiment was a pioneering particle detector located at Fermilab in the United States. As a key component of the Short-Baseline Neutrino Program, its primary mission was to investigate anomalous results from previous experiments like LSND and MiniBooNE. Utilizing advanced liquid argon time projection chamber technology, it aimed to precisely measure neutrino interactions and search for phenomena beyond the Standard Model.

Overview

MicroBooNE operated on the Booster Neutrino Beamline at Fermilab, receiving a focused beam of muon neutrinos. The experiment was designed to function as a high-resolution "electronic bubble chamber," capturing detailed images of neutrino events. Its data-taking period spanned from 2015 to 2021, contributing significantly to the global understanding of neutrino cross sections and detector technologies. The collaboration involved scientists from numerous international institutions and was a critical pathfinder for future large-scale projects like the Deep Underground Neutrino Experiment.

Physics goals

A central physics goal was to conclusively investigate the low-energy excess of electromagnetic events observed by the earlier MiniBooNE experiment. This involved determining whether the excess was due to misidentified photons from neutral current interactions or potential evidence for a sterile neutrino. The experiment also sought to make precision measurements of argon-based neutrino interaction cross sections, which are vital for the next generation of neutrino oscillation experiments. Furthermore, it provided a testbed for studying rare processes and conducting searches for physics beyond the Standard Model, including interactions mediated by hypothesized particles like the dark photon.

Detector design

The core of the detector was a 170-ton active volume liquid argon time projection chamber. This technology allows three-dimensional reconstruction of particle tracks by drifting ionization electrons through pure liquid argon onto a wire plane readout system. The chamber was housed inside a cryostat maintained at approximately 87 Kelvin. A light collection system, consisting of photomultiplier tubes behind a transparent acrylic plate, detected scintillation light to provide precise timing information. This dual-signal approach enabled superb imaging of neutrino interaction vertices and effective particle identification, distinguishing between electrons, photons, and charged pions.

Experimental results

MicroBooNE published a series of landmark results, finding no significant excess of electron-like events that would support the sterile neutrino interpretation of the MiniBooNE anomaly. Its analyses indicated that the observed excess was likely due to misidentified photons from neutral-current interactions. The collaboration produced the world's largest collection of recorded neutrino-argon scattering events, leading to numerous precision measurements of interaction cross sections. These results have heavily constrained models of sterile neutrinos and provided invaluable calibration data for the upcoming Short-Baseline Neutrino Program detectors and the Deep Underground Neutrino Experiment.

Collaboration and timeline

The MicroBooNE collaboration included over 200 physicists and engineers from more than 45 institutions across the United States, the United Kingdom, Switzerland, and other countries. Major participating institutions included Yale University, University of Cambridge, Columbia University, and Argonne National Laboratory. The project was approved in 2012, with detector construction completed in 2014. Data collection began in 2015 and concluded in 2021. The final physics analyses were completed in the subsequent years, cementing its legacy as a foundational experiment in the development of liquid argon technology and short-baseline neutrino physics.

Category:Particle physics experiments Category:Fermilab Category:Neutrino experiments