Event-by-Event Direction Reconstruction of Solar Neutrinos in a High Light-Yield Liquid Scintillator

TL;DR

This paper demonstrates the first event-by-event reconstruction of solar neutrino directions in a large-scale high light-yield liquid scintillator detector by separating Cherenkov and scintillation light using timing information.

Contribution

It introduces a novel method to reconstruct individual neutrino directions by separating Cherenkov light from scintillation light in a large detector.

Findings

Successful separation of Cherenkov and scintillation light using timing.

Clear directional correlation with the solar angle observed.

First demonstration of event-by-event direction reconstruction in such a detector.

Abstract

The direction of individual $^8$B solar neutrinos has been reconstructed using the SNO+ liquid scintillator detector. Prompt, directional Cherenkov light was separated from the slower, isotropic scintillation light using time information, and a maximum likelihood method was used to reconstruct the direction of individual scattered electrons. A clear directional signal was observed, correlated with the solar angle. The observation was aided by a period of low primary fluor concentration that resulted in a slower scintillator decay time. This is the first time that event-by-event direction reconstruction in high light-yield liquid scintillator has been demonstrated in a large-scale detector.