Search for an Excess of Electron Neutrino Interactions in MicroBooNE Using Multiple Final State Topologies

Abstract: We present a measurement of electron neutrino interactions from the Fermilab Booster Neutrino Beam using the MicroBooNE liquid argon time projection chamber to address the nature of the excess of low energy interactions observed by the MiniBooNE collaboration. Three independent electron neutrino searches are performed across multiple single electron final states, including an exclusive search for two-body scattering events with a single proton, a semi-inclusive search for pion-less events, and a fully inclusive search for events containing all hadronic final states. With differing signal topologies, statistics, backgrounds, reconstruction algorithms, and analysis approaches, the results are found to be consistent with the nominal electron neutrino rate expectations from the Booster Neutrino Beam and no excess of electron neutrino events is observed.

Analysis of Electron Neutrino Interactions in the MicroBooNE Experiment

The paper titled "Search for an Excess of Electron Neutrino Interactions in MicroBooNE Using Multiple Final State Topologies" evaluates the occurrence of electron neutrino ((\nu_e)) interactions in the MicroBooNE experiment, which utilizes a Liquid Argon Time Projection Chamber (LArTPC) at Fermilab. This study aims to explore the excess low-energy electromagnetic activity previously observed by the MiniBooNE collaboration.

Methodology

The paper presents three distinct search strategies for (\nu_e) interactions, exploring multiple final state topologies:

1. Exclusive Two-Body Scattering ((1e1p) CCQE): This selection is focused on charged current quasi-elastic interactions, leveraging deep learning techniques to analyze the kinematics of two-body events. It covers (\nu_e) events with a single electron and proton in the final state, seeking to isolate events aligned with CCQE kinematic constraints.

2. Pionless Scattering ((1eNp0\pi), (1e0p0\pi)): Utilizing the Pandora pattern recognition framework, this analysis scrutinizes final states containing electrons and protons but devoid of pions. The selection aims to replicate the electron-like signal characteristics observed in MiniBooNE.

3. Inclusive Scattering ((1eX)): An inclusive approach is employed using the Wire-Cell reconstruction methodology. This method probes all potential hadronic outcomes, providing insights and comparative data for broader analysis, including higher energy neutrino events which are expected in forthcoming DUNE experiments.

The search methodologies implement independent reconstruction algorithms and are augmented by constraints derived from high-purity (\nu_\mu) and (\pi^0) samples.

Results and Interpretation

The findings across these analyses consistently yield no substantial excess of (\nu_e) interactions within the MicroBooNE data. Statistical tests comparing the observed data with predictions derived from simulated intrinsic (\nu_e) events show that observations are either consistent with or fall modestly below expected values, particularly in regions of lower energy.

The study tackles the hypothesis of a MiniBooNE-like (\nu_e) excess through statistical tests incorporating an energy-dependent event rate model based on the MiniBooNE observations. The primary statistical test is structured around a (\Delta\chi^2) comparison, generating confidence intervals for potential excess strengths in each topology search. Most notably, the results fit well within the scenarios excluding a MiniBooNE-like excess, presenting significant deviations from the anticipated signal strength of (x=1) typically expected from MiniBooNE data.

Implications and Future Perspective

This paper's outcomes suggest that the MiniBooNE anomaly may not originate from enhanced (\nu_e) interaction rates, thereby disfavoring simplistic interpretations linking (\nu_e) interactions as the sole contributor to the excess. The findings emphasize MicroBooNE's capabilities in closely examining the nature of (\nu_e) events, creating the groundwork for further investigations and providing an essential benchmark for future SBND analyses and DUNE installations.

Future studies should focus on exploring alternative explanations or mechanisms that could elucidate the MiniBooNE results, such as potential contributions from new physics scenarios or sterile neutrino models. Moreover, ongoing efforts to improve the sensitivity and systematic constraint mechanisms within MicroBooNE will enhance the accuracy of neutrino interaction measurements, paving the way for more refined and comprehensive understanding of electromagnetic excess in large-scale neutrino detectors.