A Standard Model explanation for the MiniBooNE anomaly

TL;DR

This paper analyzes MiniBooNE data considering photon backgrounds, showing that including these backgrounds reduces the significance of the low-energy excess previously attributed to new physics.

Contribution

It introduces a detailed model of photon backgrounds in MiniBooNE, explaining part of the excess with standard physics, which was not accounted for in earlier analyses.

Findings

Photon background can explain part of the MiniBooNE excess.

The significance of unexplained events drops from 5.1σ to 3.6σ.

Photon production scales with nuclear surface area and atomic number.

Abstract

We present the results of a new analysis of the data of the MiniBooNE experiment taking into account the additional background of photons. MiniBooNE normalises the rate of photon production to the measured $\pi^0$ production rate. We study neutral current (NC) neutrino-induced $\pi^0$/photon production ($\nu_\mu + A \to \nu_\mu +1\pi^0 / \gamma + X$) on carbon nucleus (A=12). Our conclusion is based on experimental data for photon-nucleus interactions from the A2 collaboration at the Mainz MAMI accelerator. We work in the approximation that decays of the intermediate states (non-resonant N, $\Delta$ resonance, higher resonances) unaffected by its production channel, via photon or Z boson. $1\pi^0+X$ production scales as A$^{2/3}$, the surface area of the nucleus. Meanwhile the photons incoherently created in intermediate states decays will leave the nucleus, and that cross section will be proportional to the atomic number of the nucleus. We also took into account the coherent emission of photons. We show that the new photon background can explain part of the MiniBooNE low-energy excess, thus significantly lowering the number of unexplained MiniBooNE electron-like events from $5.1\sigma$ to $3.6\sigma$.