First evidence of neutrino absorption on argon using $^{8}$B solar neutrinos in DEAP-3600

TL;DR

This paper presents the first experimental evidence of electron neutrino absorption on argon from $^{8}$B solar neutrinos, using the DEAP-3600 detector with a significance of 4.0 sigma.

Contribution

It provides the first measurement of the CC $ u_e$ cross section on argon from solar neutrinos, showing a higher value than previous theoretical predictions.

Findings

Observed 6 neutrino-like events consistent with $^{8}$B spectrum.

Measured cross section is approximately 2.4 times higher than prior predictions.

Achieved 4.0 sigma significance over background.

Abstract

We report experimental evidence for electron neutrino charged-current interactions (neutrino absorption, CC $\nu_e$) from $^{8}$B solar neutrinos on $^{40}$Ar using an exposure of ($7.29 \pm 0.05$) tonne$\cdot$years in the DEAP-3600 detector. A region of interest (ROI) of 10.5-13.0 MeV reconstructed energy calibrated on single-peak events, corresponding to incident neutrino energy in 12.0-14.5 MeV, is used for this measurement. We observe 5 single-peak and 1 double-peak neutrino-like events consistent with the $^{8}$B solar neutrino energy spectrum in the ROI after correcting for nonlinearities in the detector response at high energies. With an expected background of $0.48~^{+0.16}_{-0.15}$ events, the data correspond to a significance of $4.0\,\sigma$ with respect to the background-only hypothesis. We report an energy-averaged cross section of $(4.0~^{+2.0}_{-1.6}~\mathrm{(stat)}~^{+0.8}_{-0.7}~\mathrm{(sys)})\times 10^{-41}\,\mathrm{cm}^2$ in the ROI for the CC $\nu_{e}$ signal, a factor $(2.4~^{+1.3}_{-1.0})$ higher than predicted by Bhattacharya, Goodman and Garc\'ia (2009).