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T2K Collaboration(Abe, K. et al), Antonova, M., Cervera-Villanueva, A., Fernandez, P., Izmaylov, A., & Novella, P. (2018). Search for CP Violation in Neutrino and Antineutrino Oscillations by the T2K Experiment with 2.2 x 10(21) Protons on Target. Phys. Rev. Lett., 121(17), 171802–9pp.
Abstract: The T2K experiment measures muon neutrino disappearance and electron neutrino appearance in accelerator-produced neutrino and antineutrino beams. With an exposure of 14.7(7.6) x 10(20) protons on target in the neutrino (antineutrino) mode, 89 nu(e) candidates and seven anti-nu(e) candidates are observed, while 67.5 and 9.0 are expected for delta(CP) = 0 and normal mass ordering. The obtained 2 sigma confidence interval for the CP-violating phase, delta(CP), does not include the CP-conserving cases (delta(CP) = 0, pi). The best-fit values of other parameters are sin(2) theta(23) = 0.526(-0.036)(+0.032) and Delta m(32)(2) = 2.463(-0.070)(+0.071) x 10(-3) eV(2)/c(4).
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T2K Collaboration(Abe, K. et al), Cervera-Villanueva, A., Novella, P., Izmaylov, A., Sorel, M., & Stamoulis, P. (2016). Measurement of Coherent pi(+) Production in Low Energy Neutrino-Carbon Scattering. Phys. Rev. Lett., 117(9), 192501–7pp.
Abstract: We report the first measurement of the flux-averaged cross section for charged current coherent pi(+) production on carbon for neutrino energies less than 1.5 GeV, and with a restriction on the final state phase space volume in the T2K near detector, ND280. Comparisons are made with predictions from the Rein-Sehgal coherent production model and the model by Alvarez-Ruso et al., the latter representing the first implementation of an instance of the new class of microscopic coherent models in a neutrino interaction Monte Carlo event generator. We observe a clear event excess above background, disagreeing with the null results reported by K2K and SciBooNE in a similar neutrino energy region. The measured flux-averaged cross sections are below those predicted by both the Rein-Sehgal and Alvarez-Ruso et al. models.
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Novella, P. (2015). The antineutrino energy structure in reactor experiments. Adv. High. Energy Phys., 2015, 364392–12pp.
Abstract: The recent observation of an energy structure in the reactor antineutrino spectrum is reviewed. The reactor experiments Daya Bay, Double Chooz, and RENO have reported a consistent excess of antineutrinos deviating from the flux predictions, with a local significance of about 4 sigma between 4 and 6 MeV of the positron energy spectrum. The possible causes of the structure are analyzed in this work, along with the different experimental approaches developed to identify its origin. Considering the available data and results from the three experiments, the most likely explanation concerns the reactor flux predictions and the associated uncertainties. Therefore, the different current models are described and compared. The possible sources of incompleteness or inaccuracy of such models are discussed, as well as the experimental data required to improve their precision.
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