# Scalar Non-Standard Interactions in Neutrino Oscillation

## TL;DR

This paper investigates scalar nonstandard interactions in neutrino oscillations, highlighting their unique energy-independent effects on neutrino masses and the importance of combined experimental approaches to detect them and measure CP violation.

## Contribution

It introduces the concept of scalar NSI affecting neutrino oscillations as a correction to the mass matrix, contrasting with vector NSI, and discusses their phenomenological implications.

## Key findings

- Scalar NSI can explain recent Borexino data suggesting nonzero scalar NSI.
- Scalar NSI effects are energy independent, unlike vector NSI.
- Different experimental setups are needed to identify scalar NSI and measure CP violation.

## Abstract

The scalar nonstandard interactions (NSI) can also introduce matter effect for neutrino oscillation in a medium. Especially the recent Borexino data prefers nonzero scalar NSI, $\eta_{ee} = - 0.16$. In contrast to the conventional vector NSI, the scalar type contributes as a correction to the neutrino mass matrix rather than the matter potential. Consequently, the scalar matter effect is energy independent while the vector one scales linearly with neutrino energy. This leads to significantly different phenomenological consequences in reactor, solar, atmospheric, and accelerator neutrino oscillations. A synergy of different types of experiments, especially those with matter density variation, is necessary to identify the scalar NSI and guarantee the measurement of CP violation at accelerator experiments.