Global status of neutrino oscillation parameters after Neutrino-2012

TL;DR

The paper updates the global fit of neutrino oscillation parameters by incorporating recent reactor measurements (Double Chooz, Daya Bay, RENO) and long-baseline results (MINOS, T2K). It finds a large $\sin^2\theta_{13}$, with $\theta_{13}=0$ excluded at about $10\sigma$, and shows how this strong nonzero value constrains other parameters, notably inducing a mild preference for non-maximal $\theta_{23}$. The analysis highlights tensions in atmospheric data regarding the $\theta_{23}$ octant and emphasizes the role of reactor and LB data in shaping the global picture for neutrino mixing, CP violation, and mass hierarchy studies. Overall, the work confirms a new era of precise leptonic mixing measurements and establishes a foundation for future CP-violation and mass-hierarchy investigations, aided by continued reactor experiments like Daya Bay.

Abstract

Here we update the global fit of neutrino oscillations in arXiv:1103.0734 and arXiv:1108.1376 including the recent measurements of reactor antineutrino disappearance reported by the Double Chooz, Daya Bay and RENO experiments, together with latest MINOS and T2K appearance and disappearance results, as presented at the Neutrino-2012 conference. We find that the preferred global fit value of $θ_{13}$ is quite large: $\sin^2θ_{13} \simeq 0.025$ for normal and inverted neutrino mass ordering, with $θ_{13} = 0$ now excluded at more than 10$σ$. The impact of the new $θ_{13}$ measurements over the other neutrino oscillation parameters is discussed as well as the role of the new long-baseline neutrino data and the atmospheric neutrino analysis in the determination of a non-maximal atmospheric angle $θ_{23}$.

Figures (3)

• Figure 1: Upper panels: $\Delta\chi^2$ as a function of $\sin^2\theta_{13}$ from the analysis of the total event rate in Daya Bay (solid magenta/light line), RENO (dotted line) and Double Chooz (dashed magenta/light line) as well as from the analysis of long-baseline (dashed blue/dark line) and global neutrino data (solid blue/dark line). Except for the case of the global fit here we have fixed the remaining oscillation parameters to their best fit values. Lower panels: contours of $\Delta\chi^2=1,4,9$ in the $\sin^2\theta_{13}-\delta$ plane from the global fit to the data. We minimize over all undisplayed oscillation parameters. Left (right) panels are for normal (inverted) neutrino mass hierarchy.
• Figure 2: $\Delta\chi^2$ profiles as a function of all the neutrino oscillation parameters $\sin^2\theta_{12}$, $\sin^2\theta_{23}$, $\sin^2\theta_{13}$, $\Delta m^2_{21}$, $\Delta m^2_{31}$ and $\delta$. For the central and right panels the solid lines correspond to the case of normal mass hierarchy while the dashed lines correspond to the results for the inverted mass hierarchy.
• Figure 3: Upper panels: contour regions with $\Delta \chi^2$ = 1, 4, 9 in the $\sin^2\theta_{23}$ - $\sin^2\theta_{13}$ plane from the analysis of long--baseline (MINOS and T2K) + solar + KamLAND data (left panel), long-baseline + solar + KamLAND + new Double Chooz, Daya Bay and RENO reactor data (middle panel) and the global combination (right panel) for normal hierarchy. Lower panels, same but for (inverted) neutrino mass hierarchy.