Scintillator counters with WLS fiber/MPPC readout for the side muon range detector (SMRD)of the T2K experiment

TL;DR

This paper describes the design, construction, and performance of the SMRD detector in the T2K experiment, which uses scintillator slabs with WLS fibers and MPPCs to achieve high efficiency and precise measurements of muons.

Contribution

The paper introduces a novel scintillator counter design with WLS fiber/MPPC readout for the T2K SMRD, demonstrating high efficiency and resolution.

Findings

>99% MIP detection efficiency

Light yield of 25-50 p.e./MIP

Time resolution of about 1 ns

Abstract

The T2K neutrino experiment at J-PARC uses a set of near detectors to measure the properties of an unoscillated neutrino beam and neutrino interaction cross-sections. One of the sub-detectors of the near-detector complex, the side muon range detector (SMRD), is described in the paper. The detector is designed to help measure the neutrino energy spectrum, to identify background and to calibrate the other detectors. The active elements of the SMRD consist of 0.7 cm thick extruded scintillator slabs inserted into air gaps of the UA1 magnet yokes. The readout of each scintillator slab is provided through a single WLS fiber embedded into a serpentine shaped groove. Two Hamamatsu multi-pixel avalanche photodiodes (MPPC's) are coupled to both ends of the WLS fiber. This design allows us to achieve a high MIP detection efficiency of greater than 99%. A light yield of 25-50 p.e./MIP, a time resolution of about 1 ns and a spatial resolution along the slab better than 10 cm were obtained for the SMRD counters.