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Register a new userFirst direct observation of muon antineutrino disappearance
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This letter reports the first direct observation of muon antineutrino disappearance. The MINOS experiment has taken data with an accelerator beam optimized for muon antineutrino production, accumulating an exposure of $1.71times 10^{20}$ protons on target. In the Far Detector, 97 charged current muon antineutrino events are observed. The no-oscillation hypothesis predicts 156 events and is excluded at $6.3sigma$. The best fit to oscillation yields $Delta bar{m}^{2}=(3.36^{+0.46}_{-0.40}textrm{(stat.)}pm0.06textrm{(syst.)})times 10^{-3},eV^{2}$, $sin^{2}(2bar{theta})=0.86^{+0.11}_{-0.12}textrm{(stat.)}pm0.01textrm{(syst.)}$. The MINOS muon neutrino and muon antineutrino measurements are consistent at the 2.0% confidence level, assuming identical underlying oscillation parameters.
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We report an improved measurement of muon anti-neutrino disappearance over a distance of 735km using the MINOS detectors and the Fermilab Main Injector neutrino beam in a muon anti-neutrino enhanced configuration. From a total exposure of 2.95e20 protons on target, of which 42% have not been previously analyzed, we make the most precise measurement of the anti-neutrino atmospheric delta-m squared = 2.62 +0.31/-0.28 (stat.) +/- 0.09 (syst.) and constrain the anti-neutrino atmospheric mixing angle >0.75 (90%CL). These values are in agreement with those measured for muon neutrinos, removing the tension reported previously.
The Daya Bay Reactor Neutrino Experiment has measured a non-zero value for the neutrino mixing angle $theta_{13}$ with a significance of 5.2 standard deviations. Antineutrinos from six 2.9 GW$_{rm th}$ reactors were detected in six antineutrino detectors deployed in two near (flux-weighted baseline 470 m and 576 m) and one far (1648 m) underground experimental halls. With a 43,000 ton-GW_{rm th}-day livetime exposure in 55 days, 10416 (80376) electron antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to expected number of antineutrinos at the far hall is $R=0.940pm 0.011({rm stat}) pm 0.004({rm syst})$. A rate-only analysis finds $sin^22theta_{13}=0.092pm 0.016({rm stat})pm0.005({rm syst})$ in a three-neutrino framework.
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.
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.
We report measurements by the T2K experiment of the parameters $theta_{23}$ and $Delta m^{2}_{32}$ governing the disappearance of muon neutrinos and antineutrinos in the three flavor neutrino oscillation model. Utilizing the ability of the experiment to run with either a mainly neutrino or a mainly antineutrino beam, the parameters are measured separately for neutrinos and antineutrinos. Using $7.482 times 10^{20}$ POT in neutrino running mode and $7.471 times 10^{20}$ POT in antineutrino mode, T2K obtained, $sin^{2}(theta_{23})=0.51^{+0.08}_{-0.07}$ and $Delta m^{2}_{32} = 2.53^{+0.15}_{-0.13} times 10^{-3}$eV$^{2}$/c$^{4}$ for neutrinos, and $sin^{2}({overline{theta}}_{23})=0.42^{+0.25}_{-0.07}$ and ${Deltaoverline{m}^2}_{32} = 2.55^{+0.33}_{-0.27} times 10^{-3}$eV$^{2}$/c$^{4}$ for antineutrinos (assuming normal mass ordering). No significant differences between the values of the parameters describing the disappearance of muon neutrinos and antineutrinos were observed.
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