Probing the Solar ${}^8$B Neutrino Fog with XENONnT

We report a 3.3 $\sigma$ measurement of coherent elastic neutrino-nucleus scattering from solar ${}^8$B neutrinos using a 6.77 t$\times$yr exposure from the XENONnT experiment, inferring a solar ${}^8$B neutrino flux of $(5_{-2}^{+3})\times {10}^6{\mathrm{c}\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$, consistent with previous measurements. In the presence of the ${}^8$B “neutrino fog”, we find no evidence for light dark matter, and observe diminishing returns in sensitivity with increasing exposure. A 93% increase in exposure from the previous search improves the median sensitivity to 5 GeV/$c^2$ weakly interacting massive particles-nucleon cross section by 10%. The dataset was also used to measure the weak mixing angle at $\sim$ 0.02 GeV/$c$ momentum transfer and constrain physics beyond the Standard Model.