# Confusing non-zero theta_13 with non-standard interactions in the solar neutrino sector

## TL;DR

Non-standard flavor-changing interactions in solar neutrinos can mimic the effects of a non-zero theta_13 mixing angle, complicating its precise determination from solar and KamLAND data.

## Contribution

The paper demonstrates that flavor-changing interactions can produce degeneracies with theta_13, affecting the interpretation of neutrino oscillation data.

## Key findings

- FCI can mimic non-zero theta_13 effects
- Degeneracy between FCI coupling and theta_13 quantified
- Couplings of about 10% can explain observed tensions

## Abstract

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 non-zero value of the mixing angle theta_13. Here we show that, likewise, non-standard 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 eps_e\tau^dV characterizing the non-standard transitions between nu_e and nu_tau in the forward scattering process with d-type quarks. We find that couplings with magnitude eps_e\tau^dV ~ 10%, compatible with the existing bounds, can mimic the non-zero values of theta_13 indicated by the latest analyses.