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 ${\theta }_{13}$. 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 ${\theta }_{13}$. 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 ${\theta }_{13}$ and the vectorial coupling ${ϵ}_{e\tau }^{dV}$ characterizing the nonstandard transitions between ${\nu }_e$ and ${\nu }_{\tau }$ in the forward scattering process with $d$-type quarks. We find that couplings with magnitude ${ϵ}_{e\tau }^{dV}\sim 10\%$, compatible with the existing bounds, can mimic the nonzero values of ${\theta }_{13}$ indicated by the latest analyses.

• Received 14 September 2009

DOI:https://doi.org/10.1103/PhysRevD.80.091301