Where are we with light sterile neutrinos?

Current and future neutrino oscillation constraints on leptonic unitarity

“…In this case, oscillation measurements provide a direct test of unitarity (see appendix A for discussions on the model-dependence of charged lepton decay searches). For sterile neutrinos with masses between 0.1-10 eV, dedicated searches for spectral distortions in oscillation experiments are very sensitive [55][56][57]. For heavier steriles that are still kinematically accessible, see refs.…”

eV-Scale Sterile Neutrino Search Using Eight Years of Atmospheric Muon Neutrino Data from the IceCube Neutrino Observatory

“…The standard paradigm has also been challenged, by several experiments exhibiting anomalous ν e (ν e ) appearance in ν μ (ν μ ) beams [5,6]. These anomalies can be interpreted as evidence for subleading oscillations of ν μ → ν e orν μ →ν e caused by additional neutrinos with large mass-squared differences in the range of Δm 2 ∼ 0.1-10 eV 2 [7][8][9][10][11]. On the other hand, measurements of the Z-boson decay width to invisible final states demonstrate that only three light neutrinos participate in weak interactions [12], so any additional neutrino flavor states must be nonweakly interacting, or "sterile."…”

“…Testing the 3 þ 1 model as an explanation of shortbaseline anomalies and constraining its free parameters requires measurements in multiple oscillation channels, FIG including ν μ → ν μ [24][25][26][27][28][29][30][31][32], ν e → ν e [33][34][35][36][37][38][39][40][41], and ν μ → ν e [5,6,[42][43][44]. Fits to global data [9,11,45] find a strong preference for models with sterile neutrinos over the standard three-neutrino paradigm. However, even at the most preferred values of Δm 2 ∼ 1 eV 2 , the mixing angles required to viably explain anomalies in the ν μ → ν e and ν μ →ν e channels are in strong tension with measurements of ν μ andν μ disappearance [11,45].…”

“…Fits to global data [9,11,45] find a strong preference for models with sterile neutrinos over the standard three-neutrino paradigm. However, even at the most preferred values of Δm 2 ∼ 1 eV 2 , the mixing angles required to viably explain anomalies in the ν μ → ν e and ν μ →ν e channels are in strong tension with measurements of ν μ andν μ disappearance [11,45]. These are also in tension with cosmological observations [46][47][48][49][50][51][52], though a number of possible solutions have been proposed [53][54][55][56][57][58][59][60][61][62][63].…”

“…are shown in black [25][26][27][28][29][30]123,124]; where results were not available at 99% C.L., methods of Ref. [11] were applied using public data releases. Finally, the star marks the analysis best-fit point location.…”