Confusing nonzero θ₁₃ with nonstandard interactions in the solar neutrino sector

Solar and KamLAND data are in slight tension when interpreted in the standard two-flavor oscillations framework and this may be alleviated allowing for a nonzero value of the mixing angle θ₁₃. Here we show that, likewise, nonstandard flavor-changing interactions (FCI), possibly intervening in the propagation of solar neutrinos, are equally able to alleviate this tension and therefore constitute a potential source of confusion in the determination of θ₁₃. By performing a full three-flavor analysis of solar and KamLAND data in presence of FCI we provide a quantitative description of the degeneracy existing between θ₁₃ and the vectorial coupling ϵ_eτ^dV characterizing the nonstandard transitions between ν_e and ν_τ in the forward scattering process with d-type quarks. We find that couplings with magnitude ϵ_eτ^dV∼10%, compatible with the existing bounds, can mimic the nonzero values of θ₁₃ indicated by the latest analyses.