Time variation of the atmospheric neutrino flux at dark matter detectors

TL;DR

This paper estimates how the atmospheric neutrino flux varies over the solar cycle at underground dark matter detectors, highlighting potential for timing-based discrimination of neutrino and dark matter signals.

Contribution

It provides the first detailed estimates of solar cycle-induced atmospheric neutrino flux variation at multiple dark matter detector sites.

Findings

Flux normalization varies by ~30% at high-latitude sites between solar minimum and maximum.

Variation is smaller, less than 10%, at low-latitude sites like LNGS.

Timing information can help distinguish neutrino-induced recoils from dark matter signals.

Abstract

The cosmic ray flux at the lowest energies, $\lesssim 10$ GeV, is modulated by the solar cycle, inducing a time variation that is expected to carry over into the atmospheric neutrino flux at these energies. Here we estimate this time variation of the atmospheric neutrino flux at five prospective underground locations for multi-tonne scale dark matter detectors (CJPL, Kamioka, LNGS, SNOlab and SURF). We find that between solar minimum and solar maximum, the normalization of the flux changes by $\sim 30\%$ at a high-latitude location such as SURF, while it changes by a smaller amount, $\lesssim 10\%$, at LNGS. A dark matter detector that runs for a period extending through solar cycles will be most effective at identifying this time variation. This opens the possibility to distinguish such neutrino-induced nuclear recoils from dark matter-induced nuclear recoils, thus allowing for the possibility of using timing information to break through the "neutrino floor."