KamLAND and the determination of neutrino mixing parameters in the post SNO-NC era

We study in detail the ability of the reactor experiment KamLAND for discriminating existing solutions to the solar neutrino problem and giving accurate information on neutrino masses and mixing angles. We include in this analysis the information obtained from the latest SNO-NC (neutral current measurement) results and other solar data. Assuming that the expected signal corresponding to various `benchmark' points in the two-dimensional (Δm2, tan 2θ) mixing plane, we develop a fully fledged χ2 analysis which includes the KamLAND spectrum and other existing solar evidence. A complete model of statistical and known systematical errors for 1 and 3 years of observations is included and exclusion plots are presented. We find a much higher sensitivity, in particular, for values of Δm2 lying in the central part of the large mixing angle (LMA) region. The situation would be more complicated for values that are closer to the edge of the LMA region (the HLMA region, i.e. Δm2⩽2×10-5 eV2 and Δm2⩾8 - 9×10-5 eV2 or tan 2θ far from ~0.5). In this case KamLAND, with or without any solar data, will only be able to select multiple regions in the parameter space, in the sense that different possible values of the parameters would produce the same signal. Finally, in conclusion, we point out that there is not only a problem in the determination of Δm2 in the HLMA region, but also in the discrimination of the values of the mixing angle if one considers values that are not close to the present best-fit points.