Perturbation Theory of Neutrino Oscillation with Nonstandard Neutrino Interactions

TL;DR

This paper develops a perturbative framework to analyze neutrino oscillations with non-standard interactions (NSI), providing formulas to estimate NSI effects and discussing parameter determination challenges.

Contribution

It introduces a second-order perturbation theory for neutrino oscillations with NSI, enabling estimation of NSI effects and exploring parameter degeneracies.

Findings

Second-order formulas for oscillation probabilities with NSI

Determination of , , and NSI parameters in  sector possible

Complete measurement of , , and NSI in - sector not feasible with rate analysis

Abstract

We discuss various physics aspects of neutrino oscillation with non-standard interactions (NSI). We formulate a perturbative framework by taking \Delta m^2_{21} / \Delta m^2_{31}, s_{13}, and the NSI elements \epsilon_{\alpha \beta} (\alpha, \beta = e, \mu, \tau) as small expansion parameters of the same order \epsilon. Within the \epsilon perturbation theory we obtain the S matrix elements and the neutrino oscillation probability formula to second order (third order in \nu_e related channels) in \epsilon. The formula allows us to estimate size of the contribution of any particular NSI element \epsilon_{\alpha beta} to the oscillation probability in arbitrary channels, and gives a global bird-eye view of the neutrino oscillation phenomena with NSI. Based on the second-order formula we discuss how all the conventional lepton mixing as well as NSI parameters can be determined. Our results shows that while \theta_{13}, \delta, and the NSI elements in \nu_e sector can in principle be determined, complete measurement of the NSI parameters in the \nu_\mu - \nu_\tau sector is not possible by the rate only analysis. The discussion for parameter determination and the analysis based on the matter perturbation theory indicate that the parameter degeneracy prevails with the NSI parameters. In addition, a new solar-atmospheric variable exchange degeneracy is found. Some general properties of neutrino oscillation with and without NSI are also illuminated.