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

We report a 3.3⁢𝜎 measurement of coherent elastic neutrino-nucleus scattering from solar $^8$B neutrinos using a 6.77  t×yr exposure from the XENONnT experiment, inferring a solar $^8$B neutrino flux of (5+3−2)×10$^6$  cm$^{−2}$ 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 the nucleon scattering cross section for a 5  GeV/𝑐$^2$ spin-independent weakly interacting massive particle by 10%. The dataset was also used to measure the weak mixing angle at ∼0.02  GeV/𝑐
momentum transfer and constrain physics beyond the Standard Model.