Evolution of Neutrino Mass-Mixing Parameters in Matter with Non-Standard Interactions

TL;DR

This paper investigates how non-standard neutrino interactions affect the evolution of neutrino oscillation parameters in matter, deriving analytical expressions and exploring implications for experiments like DUNE.

Contribution

It provides simple approximate analytical formulas for neutrino parameter evolution with NSI, highlighting the impact of specific NSI parameters and their signs on oscillation behavior.

Findings

NSI parameters in the (2,3) block influence θ23 evolution.

Energies relevant for DUNE show strong impact from ε_eμ and ε_eτ.

Sign flips in NSI parameters change the running patterns of oscillation parameters.

Abstract

We explore the role of matter effect in the evolution of neutrino oscillation parameters in the presence of lepton-flavor-conserving and lepton-flavor-violating neutral-current non-standard interactions (NSI) of the neutrino. We derive simple approximate analytical expressions showing the evolution/running of mass-mixing parameters in matter with energy in the presence of standard interactions (SI) and SI+NSI (considering both positive and negative values of real NSI parameters). We observe that only the NSI parameters in the (2,3) block, namely $\varepsilon_{\mu\tau}$ and $(\gamma - \beta) \equiv (\varepsilon_{\tau\tau} - \varepsilon_{\mu\mu})$ affect the running of $\theta_{23}$. Though all the NSI parameters influence the evolution of $\theta_{13}$, $\varepsilon_{e\mu}$ and $\varepsilon_{e\tau}$ show a stronger impact at the energies relevant for DUNE. $\theta_{12}$ quickly approaches to $\sim$ $90^{\circ}$ with increasing energy in both SI and SI+NSI cases. The change in $\Delta m^2_{21,m}$ is quite significant as compared to $\Delta m^2_{31,m}$ both in SI and SI+NSI frameworks. Flipping the signs of the NSI parameters alters the way in which mass-mixing parameters run with energy. We demonstrate the utility of our approach in addressing several important features related to neutrino oscillation such as: a) unraveling interesting degeneracies between $\theta_{23}$ and NSI parameters, b) estimating the resonance energy in presence of NSI when $\theta_{13}$ in matter becomes maximal, c) figuring out the required baselines and energies to have maximal matter effect in $\nu_{\mu}$ $\rightarrow$ $\nu_{e}$ transition in the presence of different NSI parameters, and d) studying the impact of NSI parameters $\varepsilon_{\mu\tau}$ and $(\gamma - \beta)$ on the $\nu_{\mu} \to \nu_{\mu}$ survival probability.