Explaining the MiniBooNE anomalous excess via a leptophilic ALP-sterile neutrino coupling
Chia-Hung V. Chang, Chuan-Ren Chen, Shu-Yu Ho, Shih-Yen Tseng
Abstract
Recently, the MiniBooNE experiment at Fermilab has updated the results with increased data and reported an excess of $560.6\ifmmode\pm\else\textpm\fi{}119.6$ electronlike events ($4.7\ensuremath{\sigma}$) 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 ($\ensuremath{\ell}\mathrm{ALP}$) and a muon neutrino. The electron-positron pairs produced from the $\ensuremath{\ell}\mathrm{ALP}$ decays can be interpreted as electronlike events provided that their opening angle is sufficiently small. In our framework, we consider the $\ensuremath{\ell}\mathrm{ALP}$ with a mass ${m}_{a}=20\text{ }\text{ }\mathrm{MeV}$ and an inverse decay constant ${c}_{e}/{f}_{a}={10}^{\ensuremath{-}2}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}1}$, allowed by the astrophysical and experimental constraints. Then, after integrating the predicted angular or visible energy spectra of the $\ensuremath{\ell}\mathrm{ALP}$ to obtain the total excess event number, we find that our scenario with sterile neutrino masses within $150\text{ }\text{ }\mathrm{MeV}\ensuremath{\lesssim}{m}_{N}\ensuremath{\lesssim}380\text{ }\text{ }\mathrm{MeV}$ ($150\text{ }\text{ }\mathrm{MeV}\ensuremath{\lesssim}{m}_{N}\ensuremath{\lesssim}180\text{ }\text{ }\mathrm{MeV}$) and neutrino mixing parameters between ${10}^{\ensuremath{-}10}\ensuremath{\lesssim}|{U}_{\ensuremath{\mu}4}{|}^{2}\ensuremath{\lesssim}{10}^{\ensuremath{-}8}$ ($3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}\ensuremath{\lesssim}|{U}_{\ensuremath{\mu}4}{|}^{2}\ensuremath{\lesssim}8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$) can explain the MiniBooNE data.