The T2K neutrino oscillation experiment established the $\nu_{\mu} \rightarrow \nu_e$ appearance with only 10\% of the original beam request of $7.8\times10^{21}$ 30 GeV protons on target (p.o.t.). In view of the J-PARC program of upgrades of the beam intensity, the T2K-II proposal requires to run up to $20\times10^{21}$ p.o.t., i.e. an increase of the exposure by more than a factor 10, aimed at establishing CP violation at $3\sigma$ level if the phase $\delta_{cp}$ is near to $-\pi/2$ and the neutrino mass ordering is normal.
The Hyper-K proposal consists of a further increase of the far detector mass by a factor 10. Facing the potential increase of statistics by two orders of magnitude, it is of great importance to undertake a vigorous program of near detector upgrades, with the aim of reducing the overall statistical and systematic uncertainties at the appropriate level of better than 4\%.
Time Projection Chambers equipped with Micro-Pattern-Gas detectors (MPGD) have been used with success for the T2K ND280 near detector and are now proposed for its upgrade, together with a novel fine-grained scintillator-based target and Time-of-Flight (ToF) detectors.
A project (CERN-SPSC-2017-002 and SPSC-EOI-015) combining the upgrade of the T2K near detector and the R\&D for a High Pressure TPC has been recently launched.
A High Pressure TPC would be a very sensitive detector for the detailed study of neutrino-nucleus interactions, a limiting factor for extracting the ultimate precision in long baseline experiments.