Three-flavour neutrino oscillation update

TL;DR

This work provides a comprehensive global assessment of three-flavour neutrino oscillations by combining solar, atmospheric, reactor, and accelerator data up to 2010. It updates the leading solar and atmospheric parameters, yielding $\Delta m^2_{21} \approx 7.6\times 10^{-5}\,\text{eV}^2$, $\sin^2\theta_{12} \approx 0.32$, $|\Delta m^2_{31}| \approx 2.40 \times 10^{-3}\,\text{eV}^2$, and $\sin^2\theta_{23} \approx 0.50$, with $\theta_{23}$ near maximal and the sign of $\Delta m^2_{31}$ still undetermined. The analysis constrains $\sin^2\theta_{13}$ to be small, with a 90% CL upper bound around $0.053$ and a best-fit near $0.013$, corresponding to a $\sim1.5\sigma$ hint for $\theta_{13}>0$ driven by a combination of solar+KamLAND and MINOS data. Overall, the results tighten the global picture of neutrino mixing, guiding future searches for CP violation and the mass hierarchy while showing that $\theta_{13}$ remains the key parameter to measure more precisely.

Abstract

We review the present status of three-flavour neutrino oscillations, taking into account the latest available neutrino oscillation data presented at the Neutrino 2008 Conference. This includes the data released this summer by the MINOS collaboration, the data of the neutral current counter phase of the SNO solar neutrino experiment, as well as the latest KamLAND and Borexino data. We give the updated determinations of the leading 'solar' and 'atmospheric' oscillation parameters. We find from global data that the mixing angle $θ_{13}$ is consistent with zero within $0.9σ$ and we derive an upper bound of $\sin^2θ_{13} < 0.035 (0.056)$ at 90% CL (3$σ$).

Figures (7)

• Figure 1: Determination of the leading "solar" oscillation parameters from the interplay of data from artificial and natural neutrino sources. We show $\chi^2$-profiles and allowed regions at 90% and 99.73% CL (2 dof) for solar and KamLAND, as well as the 99.73% CL region for the combined analysis. The dot, star and diamond indicate the best fit points of solar data, KamLAND and global data, respectively. We minimise with respect to $\Delta m^2_{31}$, $\theta_{23}$ and $\theta_{13}$, including always atmospheric, MINOS, K2K and CHOOZ data.
• Figure 2: Determination of the leading "atmospheric" oscillation parameters from the interplay of data from artificial and natural neutrino sources. We show $\chi^2$-profiles and allowed regions at 90% and 99.73% CL (2 dof) for atmospheric and MINOS, as well as the 99.73% CL region for the combined analysis (including also K2K). The dot, star and diamond indicate the best fit points of atmospheric data, MINOS and global data, respectively. We minimise with respect to $\Delta m^2_{21}$, $\theta_{12}$ and $\theta_{13}$, including always solar, KamLAND, and CHOOZ data.
• Figure 3: Constraints on $\sin^2\theta_{13}$ from different parts of the global data.
• Figure 4: Left: Allowed regions in the $(\theta_{12}-\theta_{13})$ plane at 90% and 99.73% CL (2 dof) for solar and KamLAND, as well as the 99.73% CL region for the combined analysis. $\Delta m^2_{21}$ is fixed at its best fit point. The dot, star, and diamond indicate the best fit points of solar, KamLAND, and combined data, respectively. Right: $\chi^2$ profile from solar and KamLAND data with and without the 2008 SNO-NCD data.
• Figure 5: Impact of the changes in the solar neutrino analysis. In all panels the blue (shaded) regions corresponds to the $3\sigma$ regions from solar and solar+KamLAND updated analysis. The regions delimited by the red contour curves correspond to our previous analysis (left), an analysis using the previous high-threshold SNO phase I and II analysis but the same solar model (middle), and an analysis using the high metallicity GS98 instead of our standard low metallicity AGSS09 solar model (right).