Solar neutrinos and 1-3 leptonic mixing

Abstract

Effects of the 1-3 leptonic mixing on the solar neutrino observables are studied and the signatures of non-zero ${\theta }_{13}$ are identified. For this we have re-derived the formula for $3\nu$-survival probability including all relevant corrections and constructed the iso-contours of observables in the ${\sin }^2{\theta }_{12}-{\sin }^2{\theta }_{13}$ plane. Analysis of the solar neutrino data gives ${\sin }^2{\theta }_{13}=0.007_{-0.007}^{+0.080}$ (90% C.L.) for $\Delta m^2=8\cdot 10^{-5}$ eV${}^2$. The combination of the ratio CC/NC at SNO and gallium production rate selects ${\sin }^2{\theta }_{13}=0.017\pm 0.026$ ($1\sigma$). The global fit of all oscillation data leads to zero best value of ${\sin }^2{\theta }_{13}$. The sensitivity ($1\sigma$ error) of future solar neutrino studies to ${\sin }^2{\theta }_{13}$ can be improved down to 0.01 - 0.02 by precise measurements of the pp-neutrino flux and the CC/NC ratio as well as spectrum distortion at high ($E>4$ MeV) energies. Combination of experimental results sensitive to the low and high energy parts of the solar neutrino spectrum resolves the degeneracy of angles ${\theta }_{13}$ and ${\theta }_{12}$. Comparison of ${\sin }^2{\theta }_{13}$ as well as ${\sin }^2{\theta }_{12}$ measured in the solar neutrinos and in the reactor/accelerator experiments may reveal new effects which can not be seen otherwise.

36 pages, latex, 10 figures. Analysis and figures are updated with new (salt phase II) SNO results, several clarifications added, typos corrected