Earth matter effect in Be solar neutrino experiments

We determine the sensitivity of the KamLAND and Borexino experiments to the neutrino regeneration effect in the Earth as a function of Δm² and θ, using realistic numbers for the signal and background rates. We compare the results obtained with the χ² method with those obtained from the conventional day-night asymmetry analysis. We also investigate how well one should be able to measure the neutrino oscillation parameters if a large day-night asymmetry is observed, taking the LOW solution as an example. We present an enlarged parameter space, which contains mixing angles greater than π/4 where the heavy mass eigenstate is predominantly ν_e, and determine the electron neutrino survival probability for this traditionally neglected scenario. We point out that this portion of the parameter space yields different physics results when dealing with the MSW solutions to the solar neutrino puzzle and should not be neglected.