Neutrino oscillations refitted

TL;DR

This work updates the global neutrino-oscillation fit by incorporating the latest reactor and accelerator data (Daya Bay, RENO, Double Chooz, MINOS, T2K) and revised solar results (SK-III/SK-IV). It shows that the atmospheric angle $θ_{23}$ is consistent with maximal mixing for normal ordering and near-maximal for inverted ordering, with the CP phase $δ$ now more constrained due to accelerator–reactor complementarity. The precision on $sin^2 θ_{13}$ improves, while $Δm^2_{31}$ shifts to smaller values and $δ$ is increasingly constrained toward $1.5π$; the new reactor data also increase tension for $δ≈π/2$ and influence the θ23 octant. Overall, the analysis sharpens the global picture of neutrino mixing and informs expectations for upcoming experiments.

Abstract

Here we update our previous global fit of neutrino oscillations by including the recent results which have appeared since the Neutrino-2012 conference. These include the measurements of reactor anti-neutrino disappearance reported by Daya Bay and RENO, together with latest T2K and MINOS data including both disappearance and appearance channels. We also include the revised results from the third solar phase of Super-Kamiokande, SK-III, as well as new solar results from the fourth phase of Super-Kamiokande, SK-IV. We find that the preferred global determination of the atmospheric angle $θ_{23}$ is consistent with maximal mixing. We also determine the impact of the new data upon all the other neutrino oscillation parameters with emphasis on the increasing sensitivity to the CP phase, thanks to the interplay between accelerator and reactor data. In the appendix we present the updated results obtained after the inclusion of new reactor data presented at the Neutrino 2014 conference. We discuss their impact on the global neutrino analysis.

Figures (5)

• Figure 1: 90 and 99% C.L. regions in the $\sin^2\theta_{23}$ - $\Delta m_{31}^2$ plane from separate analysis of MINOS (black lines), T2K (blue lines) and from the global analysis of all data samples (coloured regions). The left (right) panel corresponds to normal (inverted) mass ordering.
• Figure 2: 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, the same but for inverted neutrino mass hierarchy.
• Figure 3: Left panels: contour regions with $\Delta \chi^2$ = 1, 4, 9 in the $\theta_{13}$-$\delta$ plane from the analysis of LBL data alone (lines) and from the combined global analysis (coloured regions). Right panels: $\Delta\chi^2$ as a function of the CP-violating phase $\delta$ from the analysis of LBL data (dashed line) as well as from the global analysis (solid line). Upper (lower) figures correspond to NH (IH).
• Figure 4: $\Delta\chi^2$ 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 the CP phase $\delta$. For the central and right panels the solid lines correspond to the case of normal mass hierarchy while the dashed ones correspond to inverted mass hierarchy.
• Figure 5: Same as Fig. \ref{['fig:summary']} for the updated global analysis after Neutrino 2014 conference