New Oscillation Results from the T2K experiment

Abstract

The T2K (Tokai to Kamioka) experiment is a second generation long baseline neutrino oscillation experiment located in Japan. The main goal is to probe the $\theta_{13}$ neutrino mixing parameter by looking for $\nu_{\mu}\to\nu_e$ transitions in an almost pure beam of muon neutrinos. The T2K utilizes the neutirno beam produced at J-PARC (Tokai, Ibaraki) and Super-Kamiokande (Kamioka, Gifu) is used as a far detector. The experiment has been in operation since January 2010. After analyzing 1.43$\times10^{20}$ p.o.t. data collected six events are observed in far detector while the expected number with sin$^2 2\theta_{13}$=0 is 1.5$\pm$0.3. Null oscillation hypotheis leads to 7$\times10^{-3}$ probability to observe six or more candidate events, which so gives 2.5 $\sigma$ significance to the result. Thus the current T2K result is an indication of $\nu_e$ appearance due to $\nu_{\mu}\to\nu_e$ transitions. As for the first T2K $\nu_{\mu}$ disappearance data, the null oscillation hypothesis is exluded at 4.5 $\sigma$ level and the estimated atmospheric mixing parameters are consistent with the results from Super-Kamiokande and MINOS experiments.