Evidence of Antineutrinos from Distant Reactors using Pure Water at SNO+

TL;DR

This paper presents the first evidence of distant reactor antineutrinos detected in a large water Cherenkov detector, using novel analysis methods to identify signals from reactors 240 km away with a significance of 3.5 sigma.

Contribution

It demonstrates the capability of pure water Cherenkov detectors like SNO+ to detect reactor antineutrinos from distant sources, expanding neutrino detection techniques.

Findings

First evidence of reactor antineutrinos in a Cherenkov detector

Detection from reactors 240 km away with 3.5 sigma significance

Use of two analytical methods for background discrimination

Abstract

The SNO+ Collaboration reports the first evidence of reactor antineutrinos in a Cherenkov detector. The nearest nuclear reactors are located 240~km away in Ontario, Canada. This analysis uses events with energies lower than in any previous analysis with a large water Cherenkov detector. Two analytical methods are used to distinguish reactor antineutrinos from background events in 190 days of data and yield consistent evidence for antineutrinos with a combined significance of 3.5$\sigma$.