Commissioning of 3D-Segmented Neutrino Detector SuperFGD in the T2K Neutrino Beam

The Super Fine-Grained neutrino Detector (SuperFGD) is a novel fully active neutrino detector and a key element of the upgraded near off-axis detector ND280 of the T2K experiment. SuperFGD is made of approximately 2000000 optically-isolated plastic scintillator 1 cm $${}^{3}$$ cubes each one read out by three orthogonal wavelength shifting (WLS) fibers coupled to about 56000 silicon photomultipliers. The detector provides 4 $$\pi$$ particle tracking with a proton detection threshold of about 300 MeV/c. A nanosecond single-channel time resolution allows to detect neutrons produced by neutrino interactions by time-of-flight. This paper presents the results of the calibration of SuperFGD readout channels using LED system and cosmic muons, as well as the detection of muon neutrinos through charged current interactions in the T2K neutrino beam. Special attention is paid to the reconstruction of muons and stopped protons in SuperFGD.