An estimate of theta_14 independent of the reactor antineutrino flux determinations

Abstract

In a previous paper [Phys. Rev. D 83, 113013 (2011)] we have shown that the solar sector data (solar and KamLAND) are sensitive to the parameter theta_14, encoding the admixture of the electron neutrino with a fourth (essentially) sterile mass eigenstate. In that work we evidenced that such data prefer a non-zero value of theta_14 and that such a preference is completely degenerate with that of non-zero theta_13. In this report we show how the evidence of theta_13 > 0, recently emerged from global neutrino data analyses, lifts such a degeneracy and disfavors the case of sterile neutrino mixing. By excluding from our analysis the total rate information coming from the reactor experiments we untie our results from any assumption on their flux normalization. In this way, we establish the robust upper bound sin^2 (theta_14) < 0.04 at the 90% C.L.