Earth Matter Effect in 7Be Solar Neutrino Experiments

Abstract

We determine the sensitivity of the KamLAND and Borexino experiments to the neutrino regeneration effect in the Earth as a function of Delta m^2 and theta, using realistic numbers for the signal and background rates. We compare the results obtained with the chi^2 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 pi/4 where the heavy mass eigenstate is predominantly nu_e, and determine the electron neutrino survival probability for this traditionally neglected scenario. We emphasize 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.