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

TL;DR

This paper reports the first direct detection of solar $^8$B neutrinos through coherent elastic neutrino-nucleus scattering using the XENONnT dark matter detector, confirming Standard Model predictions with a 2.73 sigma significance.

Contribution

It provides the first measurement of solar neutrino-induced nuclear recoils with a dark matter experiment, demonstrating the detector's capability for neutrino physics.

Findings

Observed 37 events above 0.5 keV with background expectation of 26.4

Measured neutrino flux consistent with previous experiments

Cross section measurement aligns with Standard Model predictions

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 ($26.4^{+1.4}_{-1.3}$) events expected from backgrounds. The background-only hypothesis is rejected with a statistical significance of 2.73 $\sigma$. 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$\nu$NS cross section on Xe of $(1.1^{+0.8}_{-0.5})\times10^{-39} \mathrm{cm}^2$ is consistent with the Standard Model prediction. This is the first direct measurement of nuclear recoils from solar neutrinos with a dark matter detector.