Sensitivity to oscillation with a sterile fourth generation neutrino from ultralow threshold neutrino-nucleus coherent scattering

We discuss prospects for probing short-range sterile neutrino oscillation using neutrino-nucleus coherent scattering with ultralow energy (~10--100 eV) recoil threshold cryogenic Ge detectors. The analysis is performed in the context of a specific and contemporary reactor-based experimental proposal, developed in cooperation with the Nuclear Science Center at Texas A University, and references developing technology based upon economical and scalable detector arrays. The baseline of the experiment is substantially shorter than existing measurements, as near as about 2 m from the reactor core, and is moreover variable, extending continuously up to a range of about 10 m. This proximity and variety combine to provide extraordinary sensitivity to a wide spectrum of oscillation scales, while facilitating the tidy cancellation of leading systematic uncertainties in the reactor source and environment. With 100 eV sensitivity, for exposures on the order of 200 kg·y, we project an estimated sensitivity to first and fourth neutrino oscillation with a mass gap Δm²~1 eV² at an amplitude sin²2θ~10^-1, or Δm²~0.2 eV² at unit amplitude. Larger exposures, around 5000 kg·y, together with 10 eV sensitivity are capable of probing more than an additional order of magnitude in amplitude.