Maximal νe oscillations, Borexino and smoking guns…

We examine the maximal νe→νs and νe→νμ,τ oscillation solutions to the solar neutrino problem. These solutions lead to roughly a 50% solar flux reduction for the large parameter range 3×10−10≲δm2/eV2≲10−3. It is known that the earth regeneration effect may cause a potentially large night-day asymmetry even for maximal neutrino oscillations. We investigate the night-day asymmetry predictions for the forthcoming Borexino measurement of the 7Be neutrinos for both maximal νe→νs and νe→νμ,τ oscillations. If y×10−8≲δm2/eV2≲4y×10−5 (with y≃0.5 for νe→νs case and y≃1 for the νe→νμ,τ case) then the maximal neutrino oscillations will lead to observable night-day asymmetries in Borexino and/or superKamiokande. With Kamland covering the high mass range, 10−5≲δm2/eV2≲10−3 and Borexino/SuperK covering the low mass range, 3×10−10≲δm2/eV2≲5×10−9 (“just so” region), essentially all of the δm2 parameter space will soon be scrutinized.