BEST potential in testing the eV-scale sterile neutrino explanation of reactor antineutrino anomalies

Baksan Experiment on Sterile Neutrino (BEST) [Gavrin et al., arXiv:1006.2103; Gavrin et al.Phys. Part. Nucl. 46, 131 (2015); Gavrin et al.Phys. Rev. D 93, 073002 (2016)] is presently at the stage of production of the artificial neutrino source ⁵¹Cr, and the gallium exposure will start in July and proceed for three months. While aiming specifically at investigating the gallium neutrino anomaly (SAGE and GALLEX experiments) [Abdurashitov et al., Phys. Rev. C 59, 2246 (1999); Abdurashitov et al.Phys. Rev. C73, 045805 (2006); Kaether et al., Phys. Lett. B 685, 47 (2010)], BEST can do more, and it is tempting to estimate its ability to test the sterile neutrino explanation of antineutrino (reactor) anomalies. We observe a moderate sensitivity to the region in model parameter space (sterile neutrino mass and mixing with an active electron neutrino) outlined by the old reactor antineutrino anomaly [Mueller et al., Phys. Rev. C 83, 054615 (2011); Huber, Phys. Rev. C 84, 024617 (2011); HuberPhys. Rev. C85, 029901 (2012)] and the best fit of DANSS experiment [Alekseev et al., Phys. Lett. B 787, 56 (2018)], while the Neutrino-4 favorite region [Serebrov et al., Pis'ma Zh. Eksp. Teor. Fiz. 109, 209 (2019)] falls right in the BEST ballpark. In particular, by analyzing SAGE+GALLEX and Neutrino-4 χ² distributions we find that Neutrino-4 results are fully consistent with the gallium anomaly, and the significance of the combined anomaly almost reaches the 4σ level. If the BEST confirms the Neutrino-4 results, the joint analysis will indicate more than the 5σ evidence for the sterile neutrino of eV-scale mass.