Coincidence-based reconstruction for reactor antineutrino detection in gadolinium-doped Cherenkov detectors

TL;DR

This paper presents a coincidence-based reconstruction algorithm for reactor antineutrino detection in gadolinium-doped Cherenkov detectors, significantly improving vertex resolution and background rejection capabilities.

Contribution

It introduces a novel combined light reconstruction method for IBD pairs in Gd-doped Cherenkov detectors, enhancing accuracy and background suppression.

Findings

Vertex resolution improved up to 4.5 times at low energies

Neutron vertex resolution improved by over 30%

Background rejection up to 94% with high signal retention

Abstract

A reconstruction algorithm has been developed to capitalize on advances in Cherenkov technology for reactor antineutrino detection. Large gadolinium-doped water (Gd-H$_2$O) Cherenkov detectors are a developing technology which use Gd loading to increase the visibility of the neutrons produced in inverse beta decay (IBD) interactions, which produce positron-neutron pairs coincident in time and space. In this paper, we describe the reconstruction which uses the combined light from both events in an IBD pair to accurately reconstruct the interaction vertex. The algorithm has been applied to the reconstruction of reactor antineutrinos in Gd-H$_2$O and in Gd-doped water-based liquid scintillator (Gd-WbLS), an advanced detector medium which is also currently in development. Compared to a single-event reconstruction, the combined reconstruction improves vertex resolution for reactor IBD positrons by up to a factor of 4.5 at the lowest energies. IBD-neutron vertex resolution was found to improve by more than 30% in most instances. Powerful background rejection with the coincidence reconstruction can be achieved by requiring a minimum quality of fit. This was found to reject up to 94% of accidental coincidences of uncorrelated background events, while retaining at least 97.5% of the IBD signal pairs.