The T2K Collaboration has published recently in Nature very exciting results showing the strongest constraint yet on the parameter that governs the breaking of the symmetry between matter and antimatter in neutrino oscillations. T2K has studied how beams of muon neutrinos and antineutrinos transition into electron neutrinos and electron antineutrinos, respectively. The parameter governing the matter/antimatter symmetry breaking in neutrino oscillation, called δcp phase, can take a value from -180º to 180º. For the first time, T2K has disfavored almost half of the possible values at the 99.7% (3σ) confidence level. This outstanding result is starting to reveal a basic property of neutrinos that have not been measured until now. This is an important step on the way to knowing whether or not neutrinos and antineutrinos behave differently. I will present in detail these new results paying attention to the description of all elements involved in the analysis. To control and reduce the experimental uncertainties in oscillation analysis, T2K also performs a set of critical measurements. I will discuss these results paying attention to the possible contribution to the oscillation results.
M. Pepe-Altarelli, G. Unal