Solar neutrino oscillation parameters after first KamLAND results

We analyze the energy spectrum of reactor neutrino events recently observed in the Kamioka Liquid Scintillator Antineutrino Detector (KamLAND) and combine them with solar and terrestrial neutrino data, in the context of two- and three-family active neutrino oscillations. In the 2ν case, we find that the solution to the solar neutrino problem at large mixing angle (LMA) is basically split into two subregions that we denote as LMA-I and LMA-II. The LMA-I solution, characterized by lower values of the squared neutrino mass gap, is favored by the global data fit. This picture is not significantly modified in the 3ν mixing case. A brief discussion is given about the discrimination of the LMA-I and LMA-II solutions with future KamLAND data. In both the 2ν and 3ν cases, we present a detailed analysis of the post-KamLAND bounds on the oscillation parameters.