Updated fit to three neutrino mixing: status of leptonic CP violation

Abstract: We present a global analysis of solar, atmospheric, reactor and accelerator neutrino data in the framework of three-neutrino oscillations based on data available in summer 2014. We provide the allowed ranges of the six oscillation parameters and show that their determination is stable with respect to uncertainties related to reactor neutrino and solar neutrino flux predictions. We find that the maximal possible value of the Jarlskog invariant in the lepton sector is 0.033 ±0.010 (±0.027) at the 1σ (3σ) level and we use leptonic unitarity triangles to illustrate the ability of global oscillation data to obtain information on CP violation. We discuss “tendencies and tensions” of the global fit related to the octant of θ₂₃ as well as the CP violating phase δ_CP. The favored values of δ_CP are around 3π/2 while values around π/2 are disfavored at about Δχ² ≃6. We comment on the non-trivial task to assign a confidence level to this Δχ² value by performing a Monte Carlo study of T2K data.