Earth matter effect in Be-7 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 Deltam(2) and t heta, using realistic numbers for the signal and background rates. We compa re the results obtained with the chi (2) method with those obtained from th e conventional day-night asymmetry analysis. We also investigate how well o ne 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 pi /4 where the heavy mass eigenstate is predominantly nu (e), and det ermine the electron neutrino survival probability for this traditionally ne glected scenario. We point out that this portion of the parameter space yie lds different physics results when dealing with the MSW solutions to the so lar neutrino puzzle and should not be neglected.