Explaining the MiniBooNE Anomalous Excess via Leptophilic ALP-Sterile Neutrino Coupling

TL;DR

This paper proposes a novel explanation for the MiniBooNE excess using a sterile neutrino decay into a leptophilic axionlike particle, which produces electronlike events consistent with observed data within specific parameter ranges.

Contribution

It introduces a new sterile neutrino decay mechanism involving a leptophilic ALP to account for MiniBooNE excess, fitting experimental constraints and providing detailed parameter space analysis.

Findings

Sterile neutrino decay can produce electronlike events via ALP emission.

The proposed model fits MiniBooNE excess with specific sterile neutrino mass and mixing parameters.

The scenario is consistent with astrophysical and experimental constraints.

Abstract

Recently, the MiniBooNE experiment at Fermilab has updated the results with increased data and reported an excess of $560.6 \pm 119.6$ electronlike events ($4.7\sigma$) in the neutrino operation mode. In this paper, we propose a scenario to account for the excess where a Dirac-type sterile neutrino, produced by a charged kaon decay through the neutrino mixing, decays into a leptophilic axionlike particle ($\ell$ALP) and a muon neutrino. The electron-positron pairs produced from the $\ell$ALP decays can be interpreted as electronlike events provided that their opening angle is sufficiently small. In our framework, we consider the $\ell$ALP with a mass $m^{}_a = 20\,\text{MeV}$ and an inverse decay constant $c^{}_e/f^{}_a = 10^{-2}\,\text{GeV}^{-1}$, allowed by the astrophysical and experimental constraints. Then, after integrating the predicted angular or visible energy spectra of the $\ell$ALP to obtain the total excess event number, we find that our scenario with sterile neutrino masses within $150\,\text{MeV}\lesssim m^{}_N \lesssim 380 \,\text{MeV}$ ($150\,\text{MeV}\lesssim m^{}_N \lesssim 180 \,\text{MeV}$) and neutrino mixing parameters between $10^{-10} \lesssim |U_{\mu 4}|^2 \lesssim 10^{-8}$ ($3\times 10^{-7} \lesssim |U_{\mu 4}|^2 \lesssim 8 \times10^{-7}$) can explain the MiniBooNE data.