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Register a new userFirst measurement of neutrino oscillation parameters using neutrinos and antineutrinos by NOvA
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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$sigma$.
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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.
The main goal of the IceCube Deep Core Array is to search for neutrinos of astrophysical origins. Atmospheric neutrinos are commonly considered as a background for these searches. We show that the very high statistics atmospheric neutrino data can be used to obtain precise measurements of the main oscillation parameters.
We present a search for differences in the oscillations of antineutrinos and neutrinos in the Super-Kamiokande -I, -II, and -III atmospheric neutrino sample. Under a two-flavor disappearance model with separate mixing parameters between neutrinos and antineutrinos, we find no evidence for a difference in oscillation parameters. Best fit antineutrino mixing is found to be at (dm2bar, sin2 2 thetabar) = (2.0x10^-3 eV^2, 1.0) and is consistent with the overall Super-K measurement.
We report results from the first search for $ u_muto u_e$ transitions by the NOvA experiment. In an exposure equivalent to $2.74times10^{20}$ protons-on-target in the upgraded NuMI beam at Fermilab, we observe 6 events in the Far Detector, compared to a background expectation of $0.99pm0.11$ (syst.) events based on the Near Detector measurement. A secondary analysis observes 11 events with a background of $1.07pm0.14$ (syst.). The $3.3sigma$ excess of events observed in the primary analysis disfavors $0.1pi < delta_{CP} < 0.5pi$ in the inverted mass hierarchy at the 90% C.L.
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.
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