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Accepted · first revision · record

Title: What is the source of the MiniBooNE low-energy excess?
Plain: MiniBooNE saw extra events at low energy that look like electrons, but its detector could not tell electrons from photons.
Precise: Identify whether the MiniBooNE low-energy excess (reconstructed $E_{\nu}$ between 200 and 475 MeV) is from electrons, single photons, e+e- pairs or mismodeled backgrounds such as $\Delta \to \mathrm{N}\gamma$ and $\pi0$ misidentification. An answer assigns the excess to a specific final state with $\ge 3\sigma$ confidence.
Settled by: Liquid-argon TPC measurements in the same beam that separate electrons from photons by dE/dx (MicroBooNE, SBND, ICARUS).
Kind: well-posed
Answer type: identification
References: (empty)
Literature status: open
Status note: MicroBooNE results (2021 to 2025) disfavor $\nu_e$ and $\Delta$ radiative explanations of the full excess, leaving its source unidentified.
Posed since: (empty)