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

Abstract

We present the first measurement of nuclear recoils from solar ${}^8$B 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$\times$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 $\ddot{I}ƒ$. The measured ${}^8$B solar neutrino flux of $(4.7_{-2.3}^{+3.6})\times 10^6{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$ is consistent with results from the Sudbury Neutrino Observatory. The measured neutrino flux-weighted CE$\hat{I}½$NS cross section on Xe of $(1.1_{-0.5}^{+0.8})\times 10^{-39}{\mathrm{cm}}^2$ is consistent with the Standard Model prediction. This is the first direct measurement of nuclear recoils from solar neutrinos with a dark matter detector.