Abstract
We evaluate the statistical significance of the 3+1 sterile-neutrino hypothesis using νe and overline{nu} e disappearance data from reactor, solar and gallium radioactive source experiments. Concerning the latter, we investigate the implications of the recent BEST results. For reactor data we focus on relative measurements independent of flux predictions. For the problem at hand, the usual χ2-approximation to hypothesis testing based on Wilks’ theorem has been shown in the literature to be inaccurate. We therefore present results based on Monte Carlo simulations, and find that this typically reduces the significance by roughly 1 σ with respect to the naïve expectation. We find no significant indication in favor of sterile-neutrino oscillations from reactor data. On the other hand, gallium data (dominated by the BEST result) show more than 5 σ of evidence supporting the sterile-neutrino hypothesis, favoring oscillation parameters in agreement with constraints from reactor data. This explanation is, however, in significant tension (∼ 3 σ) with solar neutrino experiments. In order to assess the robustness of the signal for gallium experiments we present a discussion of the impact of cross-section uncertainties on the results.
Highlights
That past experiments were observing a deficit of the same magnitude
We evaluate the statistical significance of the 3+1 sterile-neutrino hypothesis using νe and νe disappearance data from reactor, solar and gallium radioactive source experiments
We present a global fit of up-to-date results from the DANSS, NEOS, PROSPECT, STEREO and Neutrino-4 reactor experiments, the past gallium results from SAGE and GALLEX, as well as the recent BEST result and solar-neutrino results in the framework of one additional sterile neutrino
Summary
We provide a brief summary of the reactor experiments whose data we have used; detailed descriptions of our analyses — including the precise forms of the χ2 functions and our techniques for generating pseudo data — are presented in appendix A. At DANSS, the detector is located on a movable platform under an industrial 3.1 GWth reactor [14] It measures the neutrino spectrum at three baselines: bottom, middle and top (I ≡ B, M, T , respectively). NIi stands for the event rates the energy bin i and ∆tI is the corresponding exposure time period for each detector location I. We get a total event rate for the top baseline of i niT = 4132.61 events per day, for energies between 1.5–6 MeV (in prompt energy). We use the first 19 bins for the combined phase-1 and phase-2 data sets Further details on our χ2 implementation and analysis can be found in appendix A.5 as well as in ref. Further details on our χ2 implementation and analysis can be found in appendix A.5 as well as in ref. [24]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
