The Tokai-to-Kamioka (T2K) experiment is a leading experiment in the field of neutrino oscillations. T2K has been taking data since 2010 and will continue its operation until 2027 when Hyper-Kamiokande is expected to start its operation.
Using data from the first decade, a new study has been made to measure neutrino neutral current interactions producing a single positive pion in the final state (NC1π+). This process has been only measured once in history, in Gargamelle's bubble chamber in 1978. Due to this and the fact that these interactions are difficult to separate from signal in Super-Kamiokande, the NC1π+ background is a relevant source of systematic uncertainty in T2K's oscillation analysis. The new study in this thesis, is the most detailed existing measurement of this process and the first in any modern neutrino experiment.
To enhance future measurements and enable studies so far inaccessible, T2K's hardware is being upgraded. In particular, its near detector, ND280 will be significantly enhanced by the installation of three novel technologies: two new high angle time-projection chambers (HA-TPCs), a novel neutrino target named the Super-Fine-Grained-Detector (SuperFGD) and six time-of-flight panels (ToF). In the thesis, contributions have been made to the development and validation of all these technologies, ranging from the analysis of beam test data using prototypes to the proposal and testing of novel reconstruction solutions based on deep learning.