Updated global fit to three neutrino mixing: status of the hints of theta13 > 0
M. C. Gonzalez-Garcia, Michele Maltoni, Jordi Salvado
TL;DR
The paper delivers a comprehensive global fit of three-neutrino oscillations to solar, atmospheric, reactor, and accelerator data, assessing the robustness and significance of a nonzero θ_{13}. By integrating new solar inputs (Borexino spectra, SNO-LETA, Ga cross-section variations) and updated atmospheric/LBL results (SK I–III reanalysis, MINOS ν_e appearance), it quantifies how θ_{13} alters the inferred oscillation parameters and mass ordering. The global analysis finds only a modest hint for θ_{13}>0, with the solar sector favoring θ_{13}=0 while MINOS and SK data provide a small positive pull; best-fit values indicate a normal hierarchy with Δm^2_{21} ≈ 7.6×10^{-5} eV^2, Δm^2_{31} ≈ +2.46×10^{-3} eV^2, θ_{12} ≈ 34°, θ_{23} ≈ 43°, and θ_{13} ≈ 5–6°, albeit with Δχ^2 differences from the inverted ordering remaining small. These results highlight the delicate balance of diverse data sets in shaping the evidence for leptonic mixing parameters and the remaining degeneracies in the mass ordering and CP phase.
Abstract
We present an up-to-date global analysis of solar, atmospheric, reactor and accelerator neutrino data in the framework of three-neutrino oscillations. We discuss in detail the statistical significance of the observed "hint" of non-zero theta13 in the solar sector at the light of the latest experimental advances, such as the Borexino spectral data, the lower value of Gallium rate recently measured in SAGE, and the low energy threshold analysis of the combined SNO phase I and phase II. We also study the robustness of the results under changes of the inputs such as the choice of solar model fluxes and a possible modification of the Gallium capture cross-section as proposed by SAGE. In the atmospheric sector we focus on the latest results for nu_e appearance from MINOS and on the recent Super-Kamiokande results from the combined phases I, II and III, and we discuss their impact on the determination of theta13. Finally, we combine all the data into a global analysis and determine the presently allowed ranges of masses and mixing.