Abstract
We present the results of an updated fit of short-baseline neutrino oscillation data in the framework of 3+1 active-sterile neutrino mixing. We first consider νe and {overline{nu}}_e disappearance in the light of the Gallium and reactor anomalies. We discuss the implications of the recent measurement of the reactor {overline{nu}}_e spectrum in the NEOS experiment, which shifts the allowed regions of the parameter space towards smaller values of |Ue4|2. The β-decay constraints of the Mainz and Troitsk experiments allow us to limit the oscillation length between about 2 cm and 7 m at 3σ for neutrinos with an energy of 1 MeV. The corresponding oscillations can be discovered in a model-independent way in ongoing reactor and source experiments by measuring νe and {overline{nu}}_e disappearance as a function of distance. We then consider the global fit of the data on short-baseline {}_{nu_{mu}}^{left(-right)}{to}_{nu_e}^{left(-right)} transitions in the light of the LSND anomaly, taking into account the constraints from {}_{nu_e}^{left(-right)} and {}_{nu_{mu}}^{left(-right)} disappearance experiments, including the recent data of the MINOS and IceCube experiments. The combination of the NEOS constraints on |Ue4|2 and the MINOS and IceCube constraints on |Uμ4|2 lead to an unacceptable appearance-disappearance tension which becomes tolerable only in a pragmatic fit which neglects the MiniBooNE low-energy anomaly. The minimization of the global χ2 in the space of the four mixing parameters Δm412, |Ue4|2, |Uμ4|2, and |Uτ4|2 leads to three allowed regions with narrow Δm412 widths at Δm412 ≈ 1.7 (best-fit), 1.3 (at 2σ), 2.4 (at 3σ) eV2. The effective amplitude of short-baseline {}_{nu_{mu}}^{left(-right)}{to}_{nu_e}^{left(-right)} oscillations is limited by 0.00048 ≲ sin2 2ϑeμ ≲ 0.0020 at 3σ. The restrictions of the allowed regions of the mixing parameters with respect to our previous global fits are mainly due to the NEOS constraints. We present a comparison of the allowed regions of the mixing parameters with the sensitivities of ongoing experiments, which show that it is likely that these experiments will determine in a definitive way if the reactor, Gallium and LSND anomalies are due to active-sterile neutrino oscillations or not.
Highlights
We consider the global fit of the data on short-baseline νμ → νe transitions in the light of the LSND anomaly, taking into account the constraints from νe and νμ disappearance experiments, including the recent data of the MINOS and IceCube experiments
We present a comparison of the allowed regions of the mixing parameters with the sensitivities of ongoing experiments, which show that it is likely that these experiments will determine in a definitive way if the reactor, Gallium and LSND anomalies are due to active-sterile neutrino oscillations or not
The MINOS and IceCube constraints on νμ and νμ disappearance are expected [38] to disfavor the low-∆m241–high-sin2 2θμμ and the low-∆m241–high-sin2 2θeμ parts of the allowed region that we found in our previous analyses [7, 12, 32, 33], as was found in the 3+1 global fit presented in ref. [39], which updated ref. [40] with the addition of the IceCube data
Summary
The reactor neutrino experiments which measured the absolute antineutrino flux that are considered in our analysis are listed in table 1. For each experiment labeled with the index a, we listed the corresponding four fission fractions fka, the ratio of measured and predicted rates Raexp, the corresponding relative experimental uncertainty σaexp, the relative uncertainty σacor which is correlated in each group of experiments indicated by the braces, and the relative theoretical uncertainty σathe which is correlated among all the experiments. The ratios of measured and predicted rates of the short-baseline experiments Bugey4 [55], Rovno91 [56], Bugey-3 [53], Gosgen [57], ILL [58, 59], Krasnoyarsk87 [60], Krasnoyarsk94 [61, 62], Rovno88 [63], and SRP [64] have been calculated by the Saclay group in
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