Maximal $\hat{I}{½}_e$ oscillations, Borexino and smoking guns

Abstract

We examine the maximal $\hat{I}{½}_e-->\hat{I}{½}_s$ and $\hat{I}{½}_e-->\hat{I}{½}_{\hat{I}}¼,\ddot{I}„$ oscillation solutions to the solar neutrino problem. These solutions lead to roughly a 50% solar flux reduction for the large parameter range $3\times 10^{-10}<\hat{I}´m^2/e{V}^2<10^{-3}$. 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 $\hat{I}{½}_e-->\hat{I}{½}_s$ and $\hat{I}{½}_e-->\hat{I}{½}_{\hat{I}}¼,\ddot{I}„$ oscillations. If $y\times 10^{-8}<\hat{I}´m^2/e{V}^2<4y\times 10^{-5}$ (with y = 0.5 for $\hat{I}{½}_e-->\hat{I}{½}_s$ case and y = 1 for $\hat{I}{½}_e-->\hat{I}{½}_{\hat{I}}¼,\ddot{I}„$ 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, $10^{-5}<\hat{I}´m^2/e{V}^2<10^{-3}$ and Borexino/superK covering the low mass range, $3\times 10^{-10}<\hat{I}´m^2/e{V}^2<5\times 10^{-9}$ ("just so" region), essentially all of the $\hat{I}´m^2$ parameter space will soon be scrutinized.

Various improvements...still about 6 pages with some figs