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; Phys. Part. Nucl. 46, 131 (2015); Phys. Rev. D 93, 073002 (2016)] is presently at the stage of production of the artificial neutrino source 51 Cr, 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); 73, 045805 (2006); Kaether et al., Phys. Lett. B 685, 47 (2010)1, 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); 85, 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 chi(2) distributions we find that Neutrino-4 results are fully consistent with the gallium anomaly, and the significance of the combined anomaly almost reaches the 4 sigma level. If the BEST confirms the Neutrino-4 results, the joint analysis will indicate more than the 5 sigma evidence for the sterile neutrino of eV-scale mass.