Development and performance evaluation of a water-based liquid scintillator tracking detector with wavelength-shifting fiber readout

TL;DR

This paper presents the development and testing of a novel water-based liquid scintillator tracking detector with wavelength-shifting fiber readout, demonstrating promising performance and highlighting improvements for neutrino interaction detection.

Contribution

The paper introduces a new water-based liquid scintillator tracking detector design, including optimized WbLS formulation and optical segmentation, with performance evaluation and improvements based on beam test results.

Findings

Good tracking performance demonstrated with a positron beam

Initial light yield was lower than expected, prompting material improvements

Significant enhancement in light yield after optimizing WbLS and separators

Abstract

We have developed a novel tracking detector utilizing a water-based liquid scintillator (WbLS) for the accurate characterization of neutrino interactions on a water target. In this detector, the WbLS is optically segmented into small cells by reflective separators, and the scintillation light is read out in three directions using wavelength-shifting fibers coupled to silicon photomultipliers. We developed and optimized WbLS samples for this application and measured their light yield using cosmic-ray muons. Subsequently, we constructed a prototype of the WbLS tracking detector and evaluated its performance with a positron beam. The beam test demonstrated good tracking performance, although the light yield was lower than required. The result prompted a review of the surfactant used in the WbLS and the material of the optical separators, leading to a significant improvement in light yield. In this paper, we report on a design of the WbLS tracking detector, the development of the WbLS, the results of the beam test, and subsequent improvements to the WbLS and optical separators.