# Measurement of the $^8$B Solar Neutrino Flux in SNO+ with Very Low Backgrounds

## TL;DR

This paper reports a precise measurement of the $^8$B solar neutrino flux using the SNO+ detector, achieving low background levels and confirming neutrino oscillation effects consistent with other experiments.

## Contribution

First measurement of $^8$B solar neutrino flux with the SNO+ detector during water commissioning, demonstrating extremely low backgrounds and consistency with neutrino oscillation models.

## Key findings

- Measured solar neutrino flux of approximately 2.53×10^6 cm^-2 s^-1
- Background rate significantly lower than the neutrino event rate
- Results consistent with matter-enhanced neutrino oscillations

## Abstract

A measurement of the $^8$B solar neutrino flux has been made using a 69.2 kt-day dataset acquired with the SNO+ detector during its water commissioning phase. At energies above 6 MeV the dataset is an extremely pure sample of solar neutrino elastic scattering events, owing primarily to the detector's deep location, allowing an accurate measurement with relatively little exposure. In that energy region the best fit background rate is $0.25^{+0.09}_{-0.07}$ events/kt-day, significantly lower than the measured solar neutrino event rate in that energy range, which is $1.03^{+0.13}_{-0.12}$ events/kt-day. Also using data below this threshold, down to 5 MeV, fits of the solar neutrino event direction yielded an observed flux of $2.53^{+0.31}_{-0.28}$(stat.)$^{+0.13}_{-0.10}$(syst.)$\times10^6$ cm$^{-2}$s$^{-1}$, assuming no neutrino oscillations. This rate is consistent with matter enhanced neutrino oscillations and measurements from other experiments.