Impact of reactor antineutrinos on the neutrino floor in low-mass WIMP-like dark matter searches

TL;DR

Reactor antineutrinos significantly impact the neutrino floor in low-mass WIMP dark matter searches, especially within 10 km of reactors, thus affecting experimental sensitivity and site selection.

Contribution

This is the first systematic study quantifying how reactor antineutrino fluxes influence the neutrino floor for low-mass WIMP detection.

Findings

Proximity to reactors within 10 km can raise the neutrino floor by up to two orders of magnitude.

Beyond 100 km, reactor contributions to the neutrino floor are negligible.

Reactor proximity is a critical factor in selecting sites for future low-threshold dark matter experiments.

Abstract

The sensitivity of conventional direct dark matter searches for weakly interacting massive particles (WIMPs) is ultimately limited by coherent elastic neutrino-nucleus scattering (CEvNS), which produces nuclear recoils indistinguishable from WIMP signals and defines the so-called neutrino floor. While the effects of solar neutrinos, geoneutrinos, diffuse supernova neutrinos, and atmospheric neutrinos have been extensively studied in this context, the contribution from reactor antineutrinos has received comparatively little attention. We present the first systematic evaluation of how reactor antineutrino fluxes, modeled as a function of reactor-detector distance, modify the neutrino floor for low-mass WIMP searches using SuperCDMS-like high-voltage germanium detectors. Both discovery-limit and opacity-based formulations of the neutrino floor are examined under consistent assumptions. We find that proximity to gigawatt-scale reactors within 10 km can raise the neutrino floor by up to a few orders of magnitude, significantly reducing the sensitivity to sub-10 GeV/c^2 dark matter. Beyond 100 km, the reactor contribution becomes negligible. These conclusions hold for both definitions of the neutrino floor and remain stable under reasonable variations in detector quenching, site-dependent geoneutrino flux, and reactor antineutrino flux uncertainties, emphasizing reactor proximity as a critical factor in site selection for future low-threshold dark matter experiments.