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Register a new userThe Experimental Status of $theta_{13}$ from the Point of View of the Electron (Anti-) Neutrino Disappearance Experiments
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Rupert Leitner
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A non zero, surprisingly large value of the third mixing angle $theta_{13}$ has been measured in reactor neutrino experiments. Currently the most precise measurement of $sin^2 2theta_{13}$ has been performed by the Daya Bay experiment $sin^22theta_{13}=0.089pm 0.010({rm stat.})pm0.005({rm syst.})$ (7.7 $sigma$ significance of $sin^22theta_{13} > 0$),the RENO experiment has measured the value $sin^2 2theta_{13} = 0.113 pm 0.013(rm stat.) pm 0.019(rm syst.)$ (4.9 $sigma$ significance) and the Double Chooz experiment $sin^2 2theta_{13} = 0.109 pm 0.030(rm stat.) pm 0.025(rm syst.)$ (2.9 $sigma$ significance). These results are extremely important for future searches of violation of combined CP parity in lepton sector of the Standard model.
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The Double Chooz experiment presents improved measurements of the neutrino mixing angle $theta_{13}$ using the data collected in 467.90 live days from a detector positioned at an average distance of 1050 m from two reactor cores at the Chooz nuclear power plant. Several novel techniques have been developed to achieve significant reductions of the backgrounds and systematic uncertainties with respect to previous publications, whereas the efficiency of the $bar u_{e}$ signal has increased. The value of $theta_{13}$ is measured to be $sin^{2}2theta_{13} = 0.090 ^{+0.032}_{-0.029}$ from a fit to the observed energy spectrum. Deviations from the reactor $bar u_{e}$ prediction observed above a prompt signal energy of 4 MeV and possible explanations are also reported. A consistent value of $theta_{13}$ is obtained from a fit to the observed rate as a function of the reactor power independently of the spectrum shape and background estimation, demonstrating the robustness of the $theta_{13}$ measurement despite the observed distortion.
This presentation describes a measurement of the neutrino mixing parameter, sin^2(2theta_13), from the Daya Bay Reactor Neutrino Experiment. Disappearance of electron antineutrinos at a distance of ~2 km from a set of six reactors, where the reactor flux is constrained by near detectors, has been clearly observed. The result, based on the ratio of observed to expected rate of antineutrinos, using 139 days of data taken between December 24, 2011 and May 11, 2012, is sin^2(2theta_13) = 0.089 +/- 0.010(stat.) +/- 0.005(syst.). Improvements in sensitivity from inclusion of additional data, spectral analysis, and improved calibration are expected in the future.
The KArlsruhe TRItium Neutrino (KATRIN) experiment is designed to measure tritium $beta$-decay spectrum with enough precision to be sensitive to neutrino mass down to 0.2eV at 90$%$ Confidence Level. After an initial first tritium run in the summer of 2018, KATRIN is taking tritium data in 2019 that should lead to a first neutrino mass result. The $beta$ spectral shape of the tritium decay is also sensitive to four countershaded Lorentz Violating (LV), oscillation-free operators within the Standard-Model Extension that may be quite large. The status and outlook of KATRIN to produce physics results, including in the LV sector, are discussed.
This paper reports the first measurement using the NOvA detectors of $ u_mu$ disappearance in a $ u_mu$ beam. The analysis uses a 14 kton-equivalent exposure of $2.74 times 10^{20}$ protons-on-target from the Fermilab NuMI beam. Assuming the normal neutrino mass hierarchy, we measure $Delta m^{2}_{32}=(2.52^{+0.20}_{-0.18})times 10^{-3}$ eV$^{2}$ and $sin^2theta_{23}$ in the range 0.38-0.65, both at the 68% confidence level, with two statistically-degenerate best fit points at $sin^2theta_{23} = $ 0.43 and 0.60. Results for the inverted mass hierarchy are also presented.
We present a measurement of neutrino oscillations via atmospheric muon neutrino disappearance with three years of data of the completed IceCube neutrino detector. DeepCore, a region of denser instrumentation, enables the detection and reconstruction of atmospheric muon neutrinos between 10 GeV and 100 GeV, where a strong disappearance signal is expected. The detector volume surrounding DeepCore is used as a veto region to suppress the atmospheric muon background. Neutrino events are selected where the detected Cherenkov photons of the secondary particles minimally scatter, and the neutrino energy and arrival direction are reconstructed. Both variables are used to obtain the neutrino oscillation parameters from the data, with the best fit given by $Delta m^2_{32}=2.72^{+0.19}_{-0.20}times 10^{-3},mathrm{eV}^2$ and $sin^2theta_{23} = 0.53^{+0.09}_{-0.12}$ (normal mass hierarchy assumed). The results are compatible and comparable in precision to those of dedicated oscillation experiments.
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