New constraints on oscillation parameters from $\nu_e$ appearance and $\nu_\mu$ disappearance in the NOvA experiment

TL;DR

The NOvA experiment's updated analysis of neutrino oscillations provides refined measurements of key parameters, favoring the normal mass hierarchy and constraining the CP-violating phase with increased data and improved methods.

Contribution

This work presents the most precise measurements to date of neutrino oscillation parameters from NOvA, with significant data and analysis improvements over previous results.

Findings

Normal mass hierarchy is favored at 95% confidence level.

Best fit oscillation parameters: Δm²₃₂=2.44×10⁻³ eV², sin²θ₂₃=0.56, δ_CP=1.21π.

Confidence intervals: Δm²₃₂ in [2.37,2.52]×10⁻³ eV², sin²θ₂₃ in [0.43,0.51]∪[0.52,0.60], δ_CP in [0,0.12π]∪[0.91π,2π].

Abstract

We present updated results from the NOvA experiment for $\nu_\mu\rightarrow\nu_\mu$ and $\nu_\mu\rightarrow\nu_e$ oscillations from an exposure of $8.85\times10^{20}$ 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 $\nu_\mu$ disappearance and $\nu_e$ appearance gives the best fit point as normal mass hierarchy, $\Delta m^2_{32} = 2.44\times 10^{-3}{{\rm eV}^2}/c^4$, $\sin^2\theta_{23} = 0.56$, and $\delta_{CP} = 1.21\pi$. The 68.3% confidence intervals in the normal mass hierarchy are $\Delta m^2_{32} \in [2.37,2.52]\times 10^{-3}{{\rm eV}^2}/c^4$, $\sin^2\theta_{23} \in [0.43,0.51] \cup [0.52,0.60]$, and $\delta_{CP} \in [0,0.12\pi] \cup [0.91\pi,2\pi]$. The inverted mass hierarchy is disfavored at the 95% confidence level for all choices of the other oscillation parameters.