Sterile Neutrino Oscillations Found at Baksan

Baksan Experiment on Sterile Transitions (BEST) https://arxiv.org/abs/2109.14654 found results pointing to a sterile neutrino, produced from oscillating electron neutrinos, squared mass difference 7.3 ev^2. The Axial force force predicts right handed neutrinos, (wouldn't be called sterile if they have another force), but not oscillation, but does predict conversion via scatterin so as would oscillation in matter would be predicted. I could not tell from the paper, weather they was a vacuum or material between the neutrino source.