[Paper Review] Observation of a Significant Excess of Electron-Like Events in the MiniBooNE Short-Baseline Neutrino Experiment

A. A. Aguilar-Arevalo, Bruce Brown+39 more|arXiv (Cornell University)|Nov 30, 2018

Particle physics theoretical and experimental studiesPhysics and Astronomy28 citations

TL;DR

The MiniBooNE experiment observes a 4.5σ excess of electron-like events (381.2 ± 85.2 events) in the 200–2500 MeV energy range, indicating a significant deviation from the Standard Model prediction. This result strengthens the case for sterile neutrino oscillations or new physics beyond the Standard Model, based on data from 12.84 × 10^20 protons on target in neutrino mode.

ABSTRACT

The MiniBooNE experiment at Fermilab reports results from an analysis of $ u_e$ appearance data from $12.84 imes 10^{20}$ protons on target in neutrino mode, an increase of approximately a factor of two over previously reported results. A $ u_e$ charged-current quasi-elastic event excess of $381.2 \pm 85.2$ events ($4.5 \sigma$) is observed in the energy range $200E_ u^{QE}

Motivation & Objective

• To search for electron neutrino appearance in a short-baseline neutrino oscillation experiment.
• To test the hypothesis of sterile neutrino oscillations that could explain anomalies in previous short-baseline experiments.
• To reduce systematic uncertainties in electron-like event detection through improved analysis techniques.
• To determine whether the observed excess of electron-like events is consistent with new physics or instrumental effects.
• To provide a high-statistics measurement of neutrino oscillations in the low-energy regime.

Proposed method

• Analysis of 12.84 × 10^20 protons on target in neutrino mode using the MiniBooNE detector.
• Identification of charged-current quasi-elastic (CCQE) electron-like events via energy deposition and particle identification.
• Application of detailed Monte Carlo simulations to model background contributions and detector response.
• Use of a blinded analysis technique to minimize bias in event selection and signal extraction.
• Comparison of observed electron-like event rates with predicted Standard Model expectations in the 200–2500 MeV energy window.
• Statistical evaluation using a significance test to quantify the deviation from the Standard Model prediction.

Experimental results

Research questions

• RQ1 Is there a significant excess of electron-like events in the MiniBooNE experiment beyond Standard Model expectations?
• RQ2 Can the observed excess be explained by sterile neutrino oscillations?
• RQ3 What is the statistical significance of the electron-like event excess in the 200–2500 MeV energy range?
• RQ4 How do improved statistics and analysis techniques affect the interpretation of the anomaly?
• RQ5 Is the observed excess consistent with background contributions or detector effects?

Key findings

• A significant excess of 381.2 ± 85.2 electron-like events is observed in the 200–2500 MeV energy range, corresponding to a 4.5σ significance.
• The observed excess is inconsistent with the Standard Model prediction, indicating a potential signal of new physics.
• The result is based on a factor-of-two increase in statistics compared to previous MiniBooNE reports.
• The excess is consistent with the CCQE channel and not explained by misidentified muons or other backgrounds.
• The significance remains robust after detailed systematic uncertainty evaluations and blinded analysis.
• The findings strengthen the case for sterile neutrino oscillations or other extensions to the Standard Model.