During the modern era of high precision neutrino physics measurements it has become increasingly important to deepen our understanding
of detector performance. It is common for neutrino detector systems to
be fully or partially composed of polystyrene-based scintillator bars, and
most experiments now gather data for over a decade. Therefore it is crucial to investigate how the performance of such sensitive materials change
T2K (Tokai to Kamioka) is a long-baseline accelerator neutrino experiment located on the East coast of Japan. It has been collecting data since
2010 and will continue until the start of the next generation experiment
Hyper-Kamiokande in 2027. Most of the subsystems of the T2K near detectors, ND280 and INGRID, will continue their operation as a part of
the Hyper-Kamiokande experiment.
The two near detectors are primarily composed of plastic scintillators
of different shapes and origin. The data they have collected provides
an opportunity to perform comprehensive studies of scintillator ageing.
This poster reports an annual light yield decrease of 0.9–2.2% recorded
by muon interactions in the near detectors. The anticipated detector response during the Hyper-Kamiokande era, and a study to disentangle the
degradation of the plastic scintillator and wavelength shifting fibres, are