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.

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