Explaining the MiniBooNE anomalous excess via a leptophilic ALP-sterile neutrino coupling

Recently, the MiniBooNE experiment at Fermilab has updated the results with increased data and reported an excess of 560.6 ± 119.6 electronlike events (4.7σ) 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 (ℓ ALP) and a muon neutrino. The electron-positron pairs produced from the ℓ ALP decays can be interpreted as electronlike events provided that their opening angle is sufficiently small. In our framework, we consider the ℓ ALP with a mass ma = 20 MeV and an inverse decay constant ce/fa = 10−2 GeV−1, allowed by the astrophysical and experimental constraints. Then, after integrating the predicted angular or visible energy spectra of the ℓ ALP to obtain the total excess event number, we find that our scenario with sterile neutrino masses within 150 MeV ≲ mN ≲ 380 MeV (150 MeV ≲ mN ≲ 180 MeV) and neutrino mixing parameters between 10 −10 ≲ |Uμ4|2 ≲ 10−8 (3 × 10−7 ≲ |Uμ4|2 ≲ 8 × 10−7) can explain the MiniBooNE data.