The oscillations of neutrinos were observed only 20 years ago, when the Super-Kamiokande collaboration observed the disappearance of atmospheric neutrinos. In less than two decades, the physics of neutrino oscillations has been the fertile field for tremendous progress. In 2012 and 2013 respectively, Daya Bay, Reno and T2K (Tokai-To-Kamioka) completed the first puzzle of neutrino oscillations by measuring the last unknown mixing angle of the PMNS matrix, θ13. Far from closing an era, these experiments opened a more promising one. Their measurements of a non-zero θ13 opened the possibility to measure the CP symmetry in the lepton sector through neutrino oscillations and, with it, the possibility to explain the asymmetry between matter and antimatter that is currently observed in our Universe.
Since 2013, SK and T2K have been the pioneer experiments that tackled this fundamental question. In particular, T2K measured a significant excess in νe, publishing the very first exclusion of CP conservation with a 90% confidence level, but has a limited sensitivity to the second remaining puzzle in neutrino oscillation: the neutrino mass-ordering. On the other hand, the atmospheric neutrino detected in Super-K offers a world-leading measurement of the neutrino mass-ordering, but with a relatively high dependency to θ23, which is extremely well-constrained by T2K.
In this seminar, we will present and discuss the results of the very first joint fit between the T2K accelerator and Super-Kamiokande atmospheric neutrinos. Using the very same Super-Kamiokande detector that can detect neutrinos from both sources, this analysis aims to provide the world's most robust probe of CP violation, mass ordering and PMNS unitarity.
