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

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 theta(13) as evident from Daya Bay) for the probability of oscillation for nu(mu) -> nu(e), taking into account NSIs at the source (epsilon(s)), the detector (epsilon(d)), and during propagation (epsilon(m)) of neutrinos through matter. Two separate cases of perturbation with small (slightly large) NSI [epsilon(m)(alpha beta) similar to 0.03(0.18)] are discussed in detail. Using various possible presently allowed NSI values we reanalyze numerically the theta(13) - delta allowed region given by recent T2K experimental data. We obtain model-independent constraints on NSIs in the delta - epsilon(m)(alpha beta) plane using the theta(13) value as measured by Daya Bay, where delta is the CP violating phase. Depending on delta values, significant constraints on epsilon(e tau) and epsilon(tau tau), in particular, are possible for both hierarchies of neutrino masses. Corresponding to T2K's 66% confidence level result, the constraints on epsilon(tau tau) are shown to be independent of any delta value.