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Register a new userAn Improved Measurement of Neutrino Oscillation Parameters by the NOvA Experiment
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We present new $ u_murightarrow u_e$, $ u_murightarrow u_mu$, $overline{ u}_murightarrowoverline{ u}_e$, and $overline{ u}_murightarrowoverline{ u}_mu$ oscillation measurements by the NOvA experiment, with a 50% increase in neutrino-mode beam exposure over the previously reported results. The additional data, combined with previously published neutrino and antineutrino data, are all analyzed using improved techniques and simulations. A joint fit to the $ u_e$, $ u_mu$, $overline{ u}_e$, and $overline{ u}_mu$ candidate samples within the 3-flavor neutrino oscillation framework continues to yield a best-fit point in the normal mass ordering and the upper octant of the $theta_{23}$ mixing angle, with $Delta m^{2}_{32} = (2.41pm0.07)times 10^{-3}$ eV$^2$ and $sin^2theta_{23} = 0.57^{+0.03}_{-0.04}$. The data disfavor combinations of oscillation parameters that give rise to a large asymmetry in the rates of $ u_e$ and $overline{ u}_e$ appearance. This includes values of the CP-violating phase in the vicinity of $delta_text{CP} = pi/2$ which are excluded by $>3sigma$ for the inverted mass ordering, and values around $delta_text{CP} = 3pi/2$ in the normal ordering which are disfavored at 2$sigma$ confidence.
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The NOvA experiment has made a $4.4sigma$-significant observation of $bar u_{e}$ appearance in a 2 GeV $bar u_{mu}$ beam at a distance of 810 km. Using $12.33times10^{20}$ protons on target delivered to the Fermilab NuMI neutrino beamline, the experiment recorded 27 $bar u_{mu} rightarrow bar u_{e}$ candidates with a background of 10.3 and 102 $bar u_{mu} rightarrow bar u_{mu}$ candidates. This new antineutrino data is combined with neutrino data to measure the oscillation parameters $|Delta m^2_{32}| = 2.48^{+0.11}_{-0.06}times10^{-3}$ eV$^2/c^4$, $sin^2 theta_{23} = 0.56^{+0.04}_{-0.03}$ in the normal neutrino mass hierarchy and upper octant and excludes most values near $delta_{rm CP}=pi/2$ for the inverted mass hierarchy by more than 3$sigma$. The data favor the normal neutrino mass hierarchy by 1.9$sigma$ and $theta_{23}$ values in the upper octant by 1.6$sigma$.
The T2K collaboration reports a precision measurement of muon neutrino disappearance with an off-axis neutrino beam with a peak energy of 0.6 GeV. Near detector measurements are used to constrain the neutrino flux and cross section parameters. The Super-Kamiokande far detector, which is 295 km downstream of the neutrino production target, collected data corresponding to $3.01 times 10^{20}$ protons on target. In the absence of neutrino oscillations, $205 pm 17$ (syst.) events are expected to be detected and only 58 muon neutrino event candidates are observed. A fit to the neutrino rate and energy spectrum assuming three neutrino flavors, normal mass hierarchy and $theta_{23}leq pi/4$ yields a best-fit mixing angle $sin^2(2theta_{23})=1.000$ and mass splitting $|Delta m^2_{32}| =2.44 times 10^{-3}$ eV$^2$/c$^4$. If $theta_{23}geq pi/4$ is assumed, the best-fit mixing angle changes to $sin^2(2theta_{23})=0.999$ and the mass splitting remains unchanged.
We present a detailed report on sterile neutrino oscillation and U-235 antineutrino energy spectrum measurement results from the PROSPECT experiment at the highly enriched High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. In 96 calendar days of data taken at an average baseline distance of 7.9 m from the center of the 85 MW HFIR core, the PROSPECT detector has observed more than 50,000 interactions of antineutrinos produced in beta decays of U-235 fission products. New limits on the oscillation of antineutrinos to light sterile neutrinos have been set by comparing the detected energy spectra of ten reactor-detector baselines between 6.7 and 9.2 meters. Measured differences in energy spectra between baselines show no statistically significant indication of antineutrinos to sterile neutrino oscillation and disfavor the Reactor Antineutrino Anomaly best-fit point at the 2.5$sigma$ confidence level. The reported U-235 antineutrino energy spectrum measurement shows excellent agreement with energy spectrum models generated via conversion of the measured U-235 beta spectrum, with a $chi^2$/DOF of 31/31. PROSPECT is able to disfavor at 2.4$sigma$ confidence level the hypothesis that U-235 antineutrinos are solely responsible for spectrum discrepancies between model and data obtained at commercial reactor cores. A data-model deviation in PROSPECT similar to that observed by commercial core experiments is preferred with respect to no observed deviation, at a 2.2$sigma$ confidence level.
We present updated results from the NOvA experiment for $ u_murightarrow u_mu$ and $ u_murightarrow u_e$ oscillations from an exposure of $8.85times10^{20}$ protons on target, which represents an increase of 46% compared to our previous publication. The results utilize significant improvements in both the simulations and analysis of the data. A joint fit to the data for $ u_mu$ disappearance and $ u_e$ appearance gives the best fit point as normal mass hierarchy, $Delta m^2_{32} = 2.44times 10^{-3}{{rm eV}^2}/c^4$, $sin^2theta_{23} = 0.56$, and $delta_{CP} = 1.21pi$. The 68.3% confidence intervals in the normal mass hierarchy are $Delta m^2_{32} in [2.37,2.52]times 10^{-3}{{rm eV}^2}/c^4$, $sin^2theta_{23} in [0.43,0.51] cup [0.52,0.60]$, and $delta_{CP} in [0,0.12pi] cup [0.91pi,2pi]$. The inverted mass hierarchy is disfavored at the 95% confidence level for all choices of the other oscillation parameters.
The OPERA experiment has conclusively observed the appearance of tau neutrinos in the muon neutrino CNGS beam. Exploiting the OPERA detector capabilities, it was possible to isolate high purity samples of $ u_{e}$, $ u_{mu}$ and $ u_{tau}$ charged current weak neutrino interactions, as well as neutral current weak interactions. In this Letter, the full dataset is used for the first time to test the three-flavor neutrino oscillation model and to derive constraints on the existence of a light sterile neutrino within the framework of the $3+1$ neutrino model. For the first time, tau and electron neutrino appearance channels are jointly used to test the sterile neutrino hypothesis. A significant fraction of the sterile neutrino parameter space allowed by LSND and MiniBooNE experiments is excluded at 90% C.L. In particular, the best-fit values obtained by MiniBooNE combining neutrino and antineutrino data are excluded at 3.3 $sigma$ significance.
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