Hint of non-standard dynamics in solar neutrino conversion

Abstract

Motivated by the recent low-threshold measurements of the solar 8B neutrino spectrum performed by Borexino, Super-Kamiokande and the Sudbury Neutrino Observatory -- all now monitoring the transition regime between low-energy (vacuum-like) and high-energy (matter-dominated) flavor conversions -- we consider the role of sub-dominant dynamical terms induced by new flavor-changing interactions. We find that the presence of such perturbations with strength ~ 0.1 G_F is now favored, offering a better description of the anomalous behavior suggested by the new results, whose spectrum shows no sign of the typical low-energy upturn predicted by the standard MSW mechanism. Our findings, if interpreted in a 2-flavor scheme, provide a hint of such new interactions at the ~ 2 sigma level, which is rather robust with respect to 3-flavor effects possibly induced by non-zero theta_13.