Hints of theta_13>0 from global neutrino data analysis

TL;DR

A global analysis of neutrino oscillation data, focusing on theta{13}, and including recent results, discusses two converging hints of theta(13)>0, each at the level of approximately 1sigma, implying a preference for theta<0 with non-negligible statistical significance.

Abstract

Nailing down the unknown neutrino mixing angle theta_13 is one of the most important goals in current lepton physics. In this context, we perform a global analysis of neutrino oscillation data, focusing on theta_13, and including recent results [Neutrino 2008, Proceedings of the XXIII International Conference on Neutrino Physics and Astrophysics, Christchurch, New Zealand, 2008 (unpublished)]. We discuss two converging hints of theta_13>0, each at the level of ~1sigma: an older one coming from atmospheric neutrino data, and a newer one coming from the combination of solar and long-baseline reactor neutrino data. Their combination provides the global estimate sin^2(theta_13) = 0.016 +- 0.010 (1sigma), implying a preference for θ_13>0 with non-negligible statistical significance (~90% C.L.). We discuss possible refinements of the experimental data analyses, which might sharpen such intriguing indication.

Figures (2)

• Figure 1: Allowed regions in the plane $(\sin^2\theta_{12},\,\sin^2\theta_{13})$: contours at $1\sigma$ (dotted) and $2\sigma$ (solid). Left and middle panels: solar (S) and KamLAND (K) data, both separately (left) and in combination (middle). In the left panel, the S contours are obtained by marginalizing the $\delta m^2$ parameter as constrained by KamLAND. Right panel: All data.
• Figure 2: Global $\nu$ oscillation analysis: Allowed $1\sigma$ ranges of $\sin^2\theta_{13}$ from different input data.