Implications of MicroBooNE's low sensitivity to electron antineutrino interactions in the search for the MiniBooNE excess

The MicroBooNE experiment searched for an excess of electron-neutrinos in the Booster Neutrino Beam (BNB), providing direct constraints on ${\nu }_e$-interpretations of the MiniBooNE low-energy excess (LEE). In this article, we show that if the MiniBooNE LEE is caused instead by an excess of ${\bar{\nu }}_e$, then liquid argon detectors, such as MicroBooNE, SBND and ICARUS, would have poor sensitivity to it. This is due to a strong suppression of ${\bar{\nu }}_e-{}^{40}$Ar cross sections in the low-energy region of the excess. The MicroBooNE results are consistent at the $2\sigma$~C.L with a scenario in which the MiniBooNE excess is sourced entirely by ${\bar{\nu }}_e$ interactions. The opportune location of ANNIE, a Gd-loaded water Cherenkov detector, allows for a direct search for a ${\bar{\nu }}_e$ flux excess in the BNB using inverse-beta-decay events.