T2K upgrades: near detector and beam

The T2K experiment is a second-generation long-baseline neutrino oscillation study aimed at exploring physics beyond the Standard Model. It uses an off-axis neutrino beam with a peak energy of around 0.6 GeV, produced at the J-PARC accelerator to investigate neutrino and antineutrino oscillations. The ND280 near detector, located at J-PARC, helps minimize systematic uncertainties related to neutrino flux and interactions. Recently, both the ND280 and the neutrino beamline underwent upgrades, enabling stable operation at 800 kW with a 10\% increase in neutrino flux. The ND280 upgrade includes a high-granularity target with 2 million optically isolated scintillating cubes, two horizontal time projection chambers (TPCs) with resistive Micromegas, and six panels of scintillating bars for precise time-of-flight measurements. These enhancements, installed in 2023-2024, are vital for improving the measurement of CP violation in the leptonic sector, aiming for greater than 3$\sigma$ significance in the second phase of T2K.