Super Fine-Grained Detector for improved neutrino interaction measurements in T2K

Parallel talk presented at the XXI International Workshop on Neutrino Telescopes - Padova 29 September - 3 October 2025 (https://agenda.infn.it/event/44606/) On behalf of the T2K SuperFGD group Abstract: The Tokai-to-Kamioka (T2K) experiment is a long-baseline neutrino experiment. T2K obtained results that exclude the CP conservation with a 90% confidence level so far. Toward more precise measurements of the oscillation parameters, T2K experiment recently started operation of upgraded near detectors to further reduce major systematic errors on the neutrino-nucleus interaction. An upstream part of the near detector complex, ND280, was replaced with three detectors: the Super Fine-Grained Detector (SuperFGD), two High-Angle TPCs (HATs), and Time of Flight detectors (ToFs). SuperFGD is a novel target tracker which consists of about two million plastic scintillator cubes packed in about 2 m x 2 m x 0.6 m dimension. Scintillation light from the cube is read out by about 56 thousand channels from three directions through wavelength-shifting fibers and photo sensors. It provides 3D track reconstruction, 4 phi angular acceptance, calorimetry, and detection capability of neutrons and low energy protons. We report detector design, construction, operation status and its performances from the physics run with a full detector starting since June 2024.