New Oscillation Results from the T2K experiment

TL;DR

The T2K experiment provides evidence for electron neutrino appearance from muon neutrino oscillations, indicating a non-zero b13 mixing angle, with results consistent with other leading neutrino experiments.

Contribution

This paper reports the first significant indication of b13-driven b1e appearance in T2K data, advancing understanding of neutrino oscillation parameters.

Findings

Six b1e candidate events observed, exceeding the null hypothesis expectation.

Null oscillation hypothesis rejected at 2.5 sigma significance.

Atmospheric mixing parameters consistent with previous experiments.

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.