Nonstandard interactions in neutrino oscillations and the recent Daya Bay and T2K experiments

Abstract

We study the possible constraints on nonstandard interaction (NSIs) in a model-independent way by considering the recent results from the T2K and Daya Bay neutrino oscillations experiments. Using the perturbation method we present generic formulas (suitable for T2K baseline and for large ${\ensuremath{\theta}}_{13}$ as evident from Daya Bay) for the probability of oscillation for ${\ensuremath{\nu}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{e}$, taking into account NSIs at the source (${ϵ}^{s}$), the detector (${ϵ}^{d}$), and during propagation (${ϵ}^{m}$) of neutrinos through matter. Two separate cases of perturbation with small (slightly large) NSI [${ϵ}_{\ensuremath{\alpha}\ensuremath{\beta}}^{m}\ensuremath{\sim}0.03(0.18)$] are discussed in detail. Using various possible presently allowed NSI values we reanalyze numerically the ${\ensuremath{\theta}}_{13}\ensuremath{-}\ensuremath{\delta}$ allowed region given by recent T2K experimental data. We obtain model-independent constraints on NSIs in the $\ensuremath{\delta}\ensuremath{-}{ϵ}_{\ensuremath{\alpha}\ensuremath{\beta}}^{m}$ plane using the ${\ensuremath{\theta}}_{13}$ value as measured by Daya Bay, where $\ensuremath{\delta}$ is the $CP$ violating phase. Depending on $\ensuremath{\delta}$ values, significant constraints on ${ϵ}_{e\ensuremath{\tau}}$ and ${ϵ}_{\ensuremath{\tau}\ensuremath{\tau}}$, in particular, are possible for both hierarchies of neutrino masses. Corresponding to T2K's 66% confidence level result, the constraints on ${ϵ}_{\ensuremath{\tau}\ensuremath{\tau}}$ are shown to be independent of any $\ensuremath{\delta}$ value.