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

We present the first measurement of nuclear recoils from solar B 8 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 × yr resulted in 37 observed events above 0.5 keV, with ( 26.4 − 1.3 + 1.4 ) events expected from backgrounds. The background-only hypothesis is rejected with a statistical significance of 2.73 σ . The measured B 8 solar neutrino flux of ( 4.7 − 2.3 + 3.6 ) × 10 6 cm − 2 s − 1 is consistent with results from the Sudbury Neutrino Observatory. The measured neutrino flux-weighted CE ν NS cross section on Xe of ( 1.1 − 0.5 + 0.8 ) × 10 − 39 cm 2 is consistent with the Standard Model prediction. This is the first direct measurement of nuclear recoils from solar neutrinos with a dark matter detector.