Characterisation of Spatial Resolution in Drift Direction for T2K's High-Angle TPCs

Poster 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 HA-TPC group Abstract: The near detectors of the T2K experiment in Japan have been upgraded with the installation of a set of three new detectors. The HA-TPCs have a novel lightweight composite field cage that allows thinner walls while maximizing the tracking volume and reducing the detector's material budget. Its readout system, Encapsulated Resistive Anode Micromegas (ERAMs), uses innovative resistive Micromegas technology, which enhances the detector's stability and robustness without compromising the spatial resolution. These technologies have been studied during several test beams and cosmic ray campaigns.These detectors were installed in the 2023 autumn and 2024 spring at the J-PARC complex. Following a commissioning phase using cosmic rays and a neutrino beam. In June 2024, HA-TPCs began taking data with the fully upgraded ND280.Residual-based analyses were performed on cosmic-ray data to evaluate spatial resolution along the drift direction and to study electric field behavior. Comparisons with Monte Carlo simulations using different noise models, along with data taken under varied electric field strengths, are presented. Funds: The research leading to these results has received funding from the Spanish Ministry of Science and Innovation PID2022-136297NB-I00/AEI/10.13039/501100011033/ FEDER, UE and through the Spanish State Research Agency, under Severo Ochoa Centres of Excellence Programme 2025-2029 (CEX2024001442-S). IFAE is partially funded by the CERCA program of the Generalitat de Catalunya. This work was supported by the European Union’s Horizon 2020 Research and Innovation programme under the H2020 Grant No. RISE-GA644294-JENNIFER 2020. With the support from the Secretariat for Universities and Research of the Ministry of Business and Knowledge of the Government of Catalonia and the European Social Fund (2022FI_B 00336).