Expérimental et théorique
For the very first time, we now have the possibility of measuring the possible violation of CP symmetry in the lepton sector through the oscillation of neutrinos, and through this, of proposing the very first brick explaining the asymmetry between matter and antimatter that we observe in our current universe. In this perspective, the current T2K experiment, and the future Hyper-Kamiokande, are the experiments best placed to realize this fundamental discovery. However, the parameterization (known as PMNS) currently used in neutrino experiments limits the universality of this discovery, as well as possible physics tests beyond the standard model. This subject proposes to rewrite the neutrino oscillation algorithm used in T2K and Hyper-Kamiokande considering a non-unitarity of the PMNS matrix, then to apply the result to the data collected by T2K since 2011 for the first time. This result will constitute a first physics search beyond the standard model by this method in T2K, as well as obtaining universal results on the violation of CP symmetry.