Time Variation of the Atmospheric Neutrino Flux at Dark Matter Detectors

The cosmic ray flux at the lowest energies, <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 multitonne minimum and solar maximum, the normalization of the flux changes by similar to 30% at a high-latitude location such as SURF, while it changes by a smaller amount, <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."