Neutrino oscillations and Non-Standard Interactions

TL;DR

This paper reviews current neutrino oscillation measurements, explores how non-standard interactions can affect parameter determination, and discusses models and methods to test and distinguish these effects.

Contribution

It provides a comprehensive review of neutrino oscillation data, analyzes the impact of non-standard interactions on measurements, and proposes ways to test and differentiate these effects from standard interactions.

Findings

Current data constrains neutrino mixing parameters with high precision.

NSI can introduce degeneracies that complicate parameter extraction.

Viable models with sizeable NC NSI can evade existing bounds.

Abstract

Current neutrino experiments measure the neutrino mixing parameters with an unprecedented accuracy. The upcoming generation of experiments will be sensitive to subdominant effects that can give information on the unknown neutrino parameters: the Dirac CP-violating phase, the mass ordering and the $\theta_{23}$ octant. Determining the exact values of neutrino mass and mixing parameters is crucial to test neutrino models and flavor symmetries. In the first part of this review, we summarize the current status of neutrino oscillation parameters. We consider the most recent data from solar experiments and the atmospheric data from Super-Kamiokande, IceCube and ANTARES. We implement the data from the reactor experiments KamLAND, Daya Bay, RENO and Double Chooz as well as the long baseline data from MINOS, T2K and NOvA. If in addition to the standard interactions, neutrinos have subdominant Non-Standard Interactions (NSI) with matter, extracting the values of these parameters will suffer from new degeneracies. We review such effects and formulate the conditions on the NSI parameters under which the precision measurement of neutrino oscillation parameters can be distorted. Like standard weak interactions, NSI can be categorized into Charged and Neutral Current NSI. Our focus will be on NC NSI since it is possible to build a class of models giving rise to sizeable NC NSI with effects on neutrino oscillations. These models are based on new $U(1)$ gauge symmetry with a boson of mass $\lesssim 10$ MeV. The UV complete model should be electroweak invariant which implies that along with neutrinos, charged fermions acquire new interactions on which there are strong bounds. We enumerate the bounds that exist on such models and show that it is possible to build viable models avoiding all the bounds. We review methods to test these models and suggest approaches to break the degeneracies caused by NSI.