Solar neutrinos and 1-3 leptonic mixing

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Abstract
Effects of the 1-3 leptonic mixing on the solar neutrino observables are studied and the signatures of nonzero θ13 are identified. For this we have rederived the formula for 3ν-survival probability including all relevant corrections and constructed the isocontours of observables in the sin2θ12−sin2θ13 plane. Analysis of the solar neutrino data gives sin2θ13=0.007−0.007+0.080 (90% C.L.) for Δm2=8×10−5 eV2. The combination of the ratio CC/NC at Sudbury Neutrino Observatory (SNO) and gallium production rate selects sin2θ13=0.017±0.026 (1σ). The global fit of all oscillation data leads to zero best value of sin2θ13. The sensitivity (1σ error) of future solar neutrino studies to sin2θ13 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 θ13 and θ12. Comparison of sin2θ13 as well as sin2θ12 measured in the solar neutrinos and in the reactor/accelerator experiments may reveal new effects which can not be seen otherwise.

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