Abstract
ND280 is a near detector of the T2K experiment which is
located in the J-PARC accelerator complex in Japan. After a decade
of fruitful data-taking, ND280 is scheduled for upgrade. The
time-of-flight (ToF) detector, which is described in this article,
is one of three new detectors that will be installed in the basket
of ND280. The ToF detector has a modular structure. Each module
represents an array of 20 plastic scintillator bars which are
stacked in a plane of 2.4 × 2.2 m2 area. Six modules of
similar construction will be assembled in a cube, thus providing an
almost 4π enclosure for an active neutrino target and two TPCs.
The light emitted by scintillator is absorbed by arrays of
large-area silicon photo-multipliers (SiPMs) which are attached to
both ends of every bar. The readout of SiPMs, shaping and analog
sum of individual SiPM signals within the array are performed by a
discrete circuit amplifier. An average time resolution of about
0.14 ns is achieved for a single bar when measured with cosmic
muons. The detector will be installed in the basket of ND280, where
it will be used to veto particle originating outside the neutrino
target, improve the particle identification and provide a cosmic
trigger for calibration of detectors which are enclosed inside it.
Background and muon counting rates in underground muon measurements with a plastic scintillator counter based on a wavelength shifting fibre and a multi-pixel avalanche photodiode readout
