NOvA results

From AstroNuWiki
Revision as of 15:37, 28 May 2021 by AnastasiaKalitkina (Talk | contribs)

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search

Analysis 2019

This analysis became the first measurement of neutrino oscillation parameters using neutrinos and antineutrinos.

The best-fit point is found for the normal hierarchy and the upper  \theta_{23} octant:

 \Delta m_{32}^2 = +2.48^{=0.11}_{-0.06} \times 10^{-3} eV^2/c^4

 sin^2 \theta_{23} = 0.56^{+0.04}_{-0.03}

 \delta_{CP} = 0.0^{+1.3}_{-0.4} \pi

The data prefer the normal hierarchy with a significance of  1.9 \sigma and the upper  \theta_{23} octant with a significance of  1.6 \sigma . These results exclude  \delta_{CP} values in the inverted mass hierarchy from  - 0.04 to  0.97\pi in the lower  \theta_{23} octant and  0.04 to  0.91\pi in the upper octant by more than  3\sigma .

Other results:

  NO, LO IH, UO IH, LO
 \Delta m_{32}^2/ (10^{-3} eV^2/c^4)  +2.47  -2.54  -2.53
 sin^2 \theta_{23}  0.48  0.56  0.47
 \delta_{CP}/ \pi  1.9  1.5  1.4
   +1.6\sigma  +1.8\sigma  +2.0\sigma

Analysis 2017

The results utilize significant improvements in both the simulations and analysis of the data. A joint fit to the data for  \nu_{\mu} disappearance and  \nu_{e} appearance gives the best-fit point as normal mass hierarchy,

 \Delta m^{2}_{32} = 2.44 \times 10^{-3} eV^{2}/c^{4} ,

 \sin^{2} \theta_{23} = 0.56 ,

 \delta_{CP} = 1.21 \pi .

The 68.3% confidence intervals in the normal mass hierarchy are

 \Delta m^{2}_{32} \in [2.37, 2.52] \times 10^{-3} eV^{2}/c^{4} ,

 \sin^{2} \theta_{23} \in [0.43, 0.51] \cup [0.52, 0.60] ,

 \delta_{CP} \in [0, 0.12\pi] \cup [0.91\pi, 2\pi] .

The inverted mass hierarchy is disfavored at the 95% confidence level for all choices of the other oscillation parameters.

Second Analysis (2016)

The results of the second analysis were published in 2017. This analysis used an exposure equivalent to  6.05 \times 10^{20} POT from the Fermilab NuMI beam.

Muon neutino disappearance results

The best fit in the normal hierarchy gives:

 \Delta m_{32}^2  = (2.67 \pm 0.11 ) \times 10^{-3} eV^2

 sin^2 \theta_{23} = 0.404^{+0.030}_{-0.022} \ (0.624^{+0.022}_{-0.030})

The best fit in the inverted hierarchy gives:

 \Delta m_{32}^2  = (-2.72 \pm 0.11 ) \times 10^{-3} eV^2

 sin^2 \theta_{23} = 0.398^{+0.030}_{-0.022} (0.618^{+0.022}_{-0.030})

Maximal mixing, where  sin^2 \theta_{23} = 0.5 , was disfavored at  2.6 \sigma.

Electron neutrino appearance results

 33 \ \nu_{e} candidates were observed with a background of  8.2 \pm 0.8 \ (syst.) .

The hypothesis of inverted mass hierarchy with  \theta_{23} in the lower octant is disfavored at greater than 93% C.L. for all values of  \delta_{CP} .


Sterile neutrinos

Sterile analysis used data collected from February 2014 to May 2016.

With an exposure of  6.05 \times 10^{20} POT-equivalent, 95 NC-like events were observe in the FD, compared with an expectation of  83.5 \pm 9.7(stat.) \pm 9.4(syst.) . This result is consistent with three-flavor mixing within 1.03 σ. No evidence for depletion of NC events is observed in the FD at a distance of 810 km from the neutrino source and NOvA sees no evidence for active-sterile neutrino mixing.

NOvA set limits of  \theta_{24} < 20.8^{\circ} and  \theta_{34} < 31.2^{\circ} in a 3+1 model scenario.

First Analysis (2015)

The results of the first analysis were published in 2016. This analysis used a 14 kton-equivalent exposure of  2.74 \times 10^{20} POT from the Fermilab NuMI beam.

Muon-neutrino disappearance results

Assuming the normal hierarchy, the measurements have a next view:

 \Delta m^{2}_{32} = 2.52^{+0.20}_{-0.18} \times 10^{-3} eV^2

and  sin^2 \theta_{23} in the 68% CL range  [0.38, 0.65] , with two statistically degenerate best-fit values:

 sin^2 \theta_{23} = 0.43 \ (0.60)

Assuming the inverted hierarchy, the measurements have a next view:

 \Delta m^{2}_{32} = -2.56 \pm 0.19 \times 10^{-3} eV^2

and  sin^2 \theta_{23} in the 68% CL range  [0.37, 0.64] , with two statistically degenerate best-fit values:

 sin^2 \theta_{23} = 0.44 \ (0.59)


Electron neutrino appearance results

NOvA had observed  6 \ \nu_{e} -like events in the FD, with a background prediction of  0.99 \pm 0.11 \ (syst.)

The range of  0.1 \pi < \delta_{CP} < 0.5\pi in the IH is disfavored at the 90% C.L. The range of  0.25 \pi < \delta_{CP} < 0.95 \pi in the NH is disfavored at the 90% C.L.