Proposal for an Electron Antineutrino Disappearance Search Using High-Rate ${}^8\mathrm{Li}$ Production and Decay

This paper introduces an experimental probe of the sterile neutrino with a novel, high-intensity source of electron antineutrinos from the production and subsequent decay of ${}^8\mathrm{Li}$. When paired with an existing $\sim 1$ kton scintillator-based detector, this $⟨E_{\nu }⟩=6.4$ MeV source opens a wide range of possible searches for beyond standard model physics via studies of the inverse beta decay interaction ${\overline{\nu }}_e+p\to e^{+}+n$. In particular, the experimental design described here has unprecedented sensitivity to ${\overline{\nu }}_e$ disappearance at $\Delta m^2\sim 1{\mathrm{eV}}^2$ and features the ability to distinguish between the existence of zero, one, and two sterile neutrinos.

Figure 1

A schematic of the IsoDAR target and surrounding volumes. The dots represent ${}^8\mathrm{Li}$ (${\overline{\nu }}_e$) creation points, obtained with ${10}^5$ 60 MeV protons on target simulated. The neutron reflector, shielding, and detector are not shown.

Figure 2

The expected antineutrino flux and detected event rate in the experimental configuration considered. The antineutrino flux mean energy from ${}^8\mathrm{Li}$ is 6.4 MeV. There are $8.2\times {10}^5$ reconstructed events expected from the $1.29\times {10}^{23}$ ${\overline{\nu }}_e$ created in the target and sleeve in five years.

Figure 3

The $L/E$ dependence of two example oscillation signatures after five years of IsoDAR running. The solid curve is the oscillation probability with no smearing in the reconstructed position and energy. The $3+2$ example (right) represents oscillations with the global best fit $3+2$ parameters from Ref. 32.

Figure 4

The sensitivity of the IsoDAR experiment to electron antineutrino disappearance in a five-year physics run. The sensitivities for both $\mathrm{\text{rate}}+\mathrm{\text{shape}}$ (solid line) and shape only (dashed line) are shown. The $\mu \mathrm{DAR}$ [33] exclusion curve and $\mathrm{\text{reactor}}+\mathrm{\text{gallium}}$ [3] allowed region are also shown, along with the expected sensitivities from the PBq source [34] and KATRIN [35] experiments.