The T2K experiment has observed electron neutrino appearance in a muon neutrino beam produced 295 km from the Super-Kamiokande detector with a peak energy of 0.6 GeV. A total of 28 electron neutrino events were detected with an energy distribution consistent with an appearance signal, corresponding to a significance of 7.3σ when compared to 4.92 ± 0.55 expected background events. In the Pontecorvo-Maki-Nakagawa-Sakata mixing model, the electron neutrino appearance signal depends on several parameters including three mixing angles θ12, θ23, θ13, a mass difference Δm232and a CP violating phase δCP. In this neutrino oscillation scenario, assuming |Δm232| = 2.4 × 10-3eV2, sin2θ23= 0.5, and Δm232> 0 (Δm232< 0), a best-fit value of sin22θ13= 0.140+0.038-0.032(0.170+0.045-0.037) is obtained at δCP= 0. When combining the result with the current best knowledge of oscillation parameters including the world average value of θ13from reactor experiments, some values of δCPare disfavored at the 90% C.L.
Publication Source (Journal or Book title)
Physical Review Letters
Abe, K., Adam, J., Aihara, H., Akiri, T., Andreopoulos, C., Aoki, S., Ariga, A., Ariga, T., Assylbekov, S., Autiero, D., Barbi, M., Barker, G., Barr, G., Bass, M., Batkiewicz, M., Bay, F., Bentham, S., Berardi, V., Berger, B., Berkman, S., Bertram, I., Bhadra, S., Blaszczyk, F., Blondel, A., Bojechko, C., Bordoni, S., Boyd, S., & Brailsford, D. (2014). Observation of electron neutrino appearance in a muon neutrino beam. Physical Review Letters, 112 (6) https://doi.org/10.1103/PhysRevLett.112.061802