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Observation of Electron Neutrino Appearance in a Muon Neutrino Beam

K. Abe et al. (T2K Collaboration)
Phys. Rev. Lett. 112, 061802 – Published 10 February 2014
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Abstract

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 Δm322 and a CP violating phase δCP. In this neutrino oscillation scenario, assuming |Δm322|=2.4×103eV2, sin2θ23=0.5, and Δm322>0 (Δm322<0), a best-fit value of sin22θ13=0.1400.032+0.038 (0.1700.037+0.045) is obtained at δCP=0. When combining the result with the current best knowledge of oscillation parameters including the world average value of θ13 from reactor experiments, some values of δCP are disfavored at the 90% C.L.

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  • Received 19 November 2013

DOI:https://doi.org/10.1103/PhysRevLett.112.061802

© 2014 American Physical Society

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Neutrino Experiments Come Closer to Seeing CP Violation

Published 10 February 2014

The T2K experiment has measured the largest number of events associated with muon neutrinos oscillating into electron neutrinos, an important step toward seeing CP violation in neutrino interactions.

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Vol. 112, Iss. 6 — 14 February 2014

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