New results from the T2K experiment

Abstract

Since its discovery, neutrino oscillation has been the subject of intense research. The ${\theta }_{13}$ parameter of the neutrino mixing matrix is of particular importance. A non-zero ${\theta }_{13}$ opens the possibility to study CP violation in the neutrino sector which could help explain the matter anti-matter asymmetry in the Universe. The Tokai-To-Kamioka (T2K) experiment was designed to measure electron neutrino appearance and muon neutrino disappearance using a muon neutrino beam produced at the J-PARC facility in Tokai, Japan. The Super-Kamiokande detector, located 295 km from the neutrino source, acts as the far detector. An improved analysis and all the data taken through June 9, 2012 provide 11 electron neutrino candidates in the far detector corresponding to 3.1 standard deviations from the ${\theta }_{13}=0$ hypothesis. This excess is currently the strongest indication of electron neutrino appearance and it yields for normal hierarchy and ${\delta }_{CP}=0$, $0.053<{\sin }^{2}2{\theta }_{13}<0.141$ at 68% confidence level.