Quasi-sterile neutrinos from dark sectors. Part I. BSM matter effects in neutrino oscillations and the short-baseline anomalies

Quasi-sterile neutrinos are a natural consequence of dark sectors interacting with the Standard Model (SM) sector via neutrino- and vector-portals. Essentially, quasi-sterile neutrinos are light dark sector fermions with two generic properties: (i) they mix with the active neutrinos of the SM, and (ii) they are charged under a vector mediator that couples feebly to SM matter. Various interesting phenomenological consequences result from this class of particles. In this article, we investigate one such consequence: new, beyond the SM matter effects that can alter in-medium neutrino oscillations. In particular, for special windows of energy and matter densities, active neutrinos can resonantly oscillate into sterile neutrinos. We take advantage of this feature to build a quasi-sterile neutrino model that can explain the MiniBooNE and LSND anomalies, while remaining compatible with observations from long-baseline reactor- and accelerator-based neutrino experiments. This model is also likely compatible with the recent results reported by the MicroBooNE collaboration (albeit we cannot precisely quantify this claim due to a lack of information in MicroBooNE's public data releases to date). Implications for solar neutrinos and nu(e) disappearance searches are also briefly discussed.

Automated summary

The article investigates the impact of quasi-sterile neutrino models on neutrino oscillations, particularly the phenomenon of active neutrinos resonantly oscillating into quasi-sterile neutrinos under specific energy and matter density conditions. The study finds that the model can explain the anomalies observed in the MiniBooNE and LSND experiments and is compatible with observations from long-baseline reactor and accelerator-based neutrino experiments.