Charged-particle veto detector for the $K_L \to \pi^0 \nu \bar\nu$ study in the J-PARC K$^O$TO experiment

TL;DR

This paper reports on the development and testing of a charged-particle veto detector designed for the rare $K_L o \pi^0 u ar{ u}$ decay study in the J-PARC KOTO experiment, achieving high light yield and good timing resolution.

Contribution

The paper introduces a novel plastic scintillator-based veto detector with wavelength shifting fibers and MPPCs, optimized for rare decay detection in the KOTO experiment.

Findings

Light yield exceeds 10 photoelectrons per 100 keV

Timing resolution is better than 3 nanoseconds in most regions

Detector performance meets the requirements for standard model sensitivity

Abstract

A charged-particle veto detector was constructed to study the rare decay $K_{L} \rightarrow \pi^{0} \nu \bar{\nu}$ in the J-PARC K$^{\mathrm{O}}$TO experiment. This detector consists of 3mm-thick plastic scintillator strips and wavelength shifting fibers coupled with MPPCs at the both ends, which makes it possible to obtain large light output over the wide region. After the construction and installation to the K$^{\mathrm{O}}$TO experimental area, its performance was studied using charged particles from $K_{\mathrm{L}}$ decays. As a preliminary result, we found that the detector had the light yield larger than 10p.e./100keV and the timing resolution better than 3ns for most regions, which satisfied the requirements to achieve the standard model sensitivety($\sim10^{-11}$) for the $K_{L} \rightarrow \pi^{0} \nu \bar{\nu}$ detection.