Non-standard interaction in neutrino oscillations and recent Daya Bay, T2K experiments

TL;DR

This paper investigates constraints on non-standard neutrino interactions using recent T2K and Daya Bay data, providing model-independent formulas and analyzing the impact on oscillation parameters and NSI bounds.

Contribution

It offers generic perturbation formulas for neutrino oscillation probabilities including NSIs and reanalyzes experimental data to constrain NSI parameters independently of specific models.

Findings

Significant constraints on  and  NSI parameters are possible.

Constraints on   are independent of the CP phase .

The analysis provides bounds on NSI parameters that depend on the neutrino mass hierarchy and CP phase .

Abstract

We study the possible constraints on non-standard interaction(NSIs) in a model independent way by considering the recent results from T2K and Daya Bay neutrino oscillations experiments. Using 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 $\nu_\mu \rightarrow \nu_e$, taking into account NSIs at source ($\epsilon^s$), detector ($\epsilon^d$) and during propagation ($\epsilon^m$) of neutrinos through matter. Two separate cases of perturbation with small (slightly large) NSI ($\epsilon_{\alpha\beta}^m \sim 0.03(0.18)$) 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 $\delta-\epsilon_{\alpha\beta}^m$ 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 $\epsilon_{\tau\tau}$ is shown to be independent of any $\delta$ value.