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

Abstract

Baksan Experiment on Sterile Neutrino (BEST) [Gavrin, arXiv:1006.2103; Gavrin Phys. Part. Nucl. 46, 131 (2015); PPNUER1063-779610.1134/S1063779615020100Gavrin Phys. Rev. D 93, 073002 (2016)PRVDAQ2470-001010.1103/PhysRevD.93.073002] is presently at the stage of production of the artificial neutrino source Cr51, 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, Phys. Rev. C 59, 2246 (1999); PRVCAN0556-281310.1103/PhysRevC.59.2246Abdurashitov Phys. Rev. C73, 045805 (2006)PRVCAN0556-281310.1103/PhysRevC.73.045805; Kaether, Phys. Lett. B 685, 47 (2010)PYLBAJ0370-269310.1016/j.physletb.2010.01.030], 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, Phys. Rev. C 83, 054615 (2011); PRVCAN0556-281310.1103/PhysRevC.83.054615Huber, Phys. Rev. C 84, 024617 (2011); PRVCAN0556-281310.1103/PhysRevC.84.024617HuberPhys. Rev. C85, 029901 (2012)PRVCAN0556-281310.1103/PhysRevC.85.029901] and the best fit of DANSS experiment [Alekseev, Phys. Lett. B 787, 56 (2018)PYLBAJ0370-269310.1016/j.physletb.2018.10.038], while the Neutrino-4 favorite region [Serebrov, Pis'ma Zh. Eksp. Teor. Fiz. 109, 209 (2019)PZETAB0370-274X10.1134/S0370274X19040015] 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.