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Register a new userMeasurement of neutrino and antineutrino oscillations by the T2K experiment including a new additional sample of $ u_e$ interactions at the far detector
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The T2K experiment reports an updated analysis of neutrino and antineutrino oscillations in appearance and disappearance channels. A sample of electron neutrino candidates at Super-Kamiokande in which a pion decay has been tagged is added to the four single-ring samples used in previous T2K oscillation analyses. Through combined analyses of these five samples, simultaneous measurements of four oscillation parameters, $|Delta m^2_{32}|$, $sin^2(theta_{23})$, $sin^2(theta_{13})$, and $delta_{CP}$ and of the mass ordering are made. A set of studies of simulated data indicates that the sensitivity to the oscillation parameters is not limited by neutrino interaction model uncertainty. Multiple oscillation analyses are performed, and frequentist and Bayesian intervals are presented for combinations of the oscillation parameters with and without the inclusion of reactor constraints on $sin^2(theta_{13})$. When combined with reactor measurements, the hypothesis of CP conservation ($delta_{CP}$$=0$ or $pi$) is excluded at 90% confidence level. The 90% confidence region for $delta_{CP}$ is [-2.95,-0.44] ([-1.47, -1.27]) for normal (inverted) ordering. The central values and 68% confidence intervals for the other oscillation parameters for normal (inverted) ordering are $Delta m^{2}_{32}=2.54pm0.08$ ($2.51pm0.08$) $times 10^{-3}$ eV$^2 / c^4$ and $sin^2(theta_{23}) = 0.55^{+0.05}_{-0.09}$ ($0.55^{+0.05}_{-0.08}$), compatible with maximal mixing. In the Bayesian analysis, the data weakly prefer normal ordering (Bayes factor 3.7) and the upper octant for $sin^2(theta_{23})$ (Bayes factor 2.4).
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T2K reports its first results in the search for CP violation in neutrino oscillations using appearance and disappearance channels for neutrino- and antineutrino-mode beam. The data include all runs from Jan 2010 to May 2016 and comprise $7.482times10^{20}$,protons on target in neutrino mode, which yielded in the far detector 32 e-like and 135 $mu$-like events, and $7.471times10^{20}$,protons on target in antineutrino mode which yielded 4 e-like and 66 $mu$-like events. Reactor measurements of $sin^{2}2theta_{13}$ have been used as an additional constraint. The one-dimensional confidence interval at 90% for $delta_{CP}$ spans the range ($-3.13$, $-0.39$) for normal mass ordering. The CP conservation hypothesis ($delta_{CP}=0,pi$) is excluded at 90% C.L.
The T2K experiment measures muon neutrino disappearance and electron neutrino appearance in accelerator-produced neutrino and antineutrino beams. With an exposure of $14.7(7.6)times 10^{20}$ protons on target in neutrino (antineutrino) mode, 89 $ u_e$ candidates and 7 anti-$ u_e$ candidates were observed while 67.5 and 9.0 are expected for $delta_{CP}=0$ and normal mass ordering. The obtained $2sigma$ 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 $sin^2theta_{23} = 0.526^{+0.032}_{-0.036}$ and $Delta m^2_{32}=2.463^{+0.071}_{-0.070}times10^{-3} mathrm{eV}^2/c^4$.
The magnetised Iron Calorimeter detector at the India-based Neutrino Observatory (INO) has a unique feature to identify the neutrinos and antineutrinos on an event by event basis. This feature can be harnessed to detect the differences between the oscillation parameters of neutrinos and antineutrinos independently. In this paper, we analysed Charged Current $ u_{mu}$ and $overline{ u}_{mu}$ events under the influence of earth matter effect using three neutrino flavor oscillation framework. If the atmospheric mass-squared differences and mixing parameters for neutrinos are different from antineutrinos, we present the prospects for the experimental observation of these differences in atmospheric $ u$ and $overline u_{mu}$ oscillations at INO. We estimate the detector sensitivity to confirm a non-zero difference in the mass-squared splittings ($|Delta m^{2}_{32}|-|Deltaoverline{m^{2}}_{32}|$) for neutrinos and antineutrinos.
We report a new measurement of electron antineutrino disappearance using the fully-constructed Daya Bay Reactor Neutrino Experiment. The final two of eight antineutrino detectors were installed in the summer of 2012. Including the 404 days of data collected from October 2012 to November 2013 resulted in a total exposure of 6.9$times$10$^5$ GW$_{rm th}$-ton-days, a 3.6 times increase over our previous results. Improvements in energy calibration limited variations between detectors to 0.2%. Removal of six $^{241}$Am-$^{13}$C radioactive calibration sources reduced the background by a factor of two for the detectors in the experimental hall furthest from the reactors. Direct prediction of the antineutrino signal in the far detectors based on the measurements in the near detectors explicitly minimized the dependence of the measurement on models of reactor antineutrino emission. The uncertainties in our estimates of $sin^{2}2theta_{13}$ and $|Delta m^2_{ee}|$ were halved as a result of these improvements. Analysis of the relative antineutrino rates and energy spectra between detectors gave $sin^{2}2theta_{13} = 0.084pm0.005$ and $|Delta m^{2}_{ee}|= (2.42pm0.11) times 10^{-3}$ eV$^2$ in the three-neutrino framework.
The disappearance of reactor antineutrinos in the Double Chooz experiment is used to investigate the possibility of neutrino-antineutrino oscillations arising due to the breakdown of Lorentz invariance. We find no evidence for this phenomenon and set the first limits on 15 coefficients describing neutrino-antineutrino mixing within the framework of the Standard-Model Extension.
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