First Measurement of Solar ⁸B Neutrinos via Coherent Elastic Neutrino-Nucleus Scattering with XENONnT

We present the first measurement of nuclear recoils from solar ⁸B neutrinos via coherent elastic neutrino-nucleus scattering with the XENONnT dark matter experiment. The central detector of XENONnT is a low-background, two-phase time projection chamber with a 5.9 t sensitive liquid xenon target. A blind analysis with an exposure of 3.51 t×y resulted in 37 observed events above 0.5 keV, with (26.4+1.4−1.3) events expected from backgrounds. The background-only hypothesis is rejected with a statistical significance of 2.73 σ. The measured ⁸B solar neutrino flux of (4.7+3.6−2.3)×106cm−2s−1 is consistent with results from dedicated solar neutrino experiments. The measured neutrino flux-weighted CEνNS cross-section on Xe of (1.1+0.8−0.5)×10−39cm2 is consistent with the Standard Model prediction. This is the first direct measurement of nuclear recoils from solar neutrinos with a dark matter detector.