Improving the Global SMEFT Picture with Bounds on Neutrino NSI

TL;DR

This paper investigates how neutrino oscillation and scattering data refine the global SMEFT analysis, revealing improved constraints on new physics operators, especially involving tau flavor and lepton flavor violation.

Contribution

It provides a detailed mapping between SMEFT parameters and NSI, and demonstrates the enhanced constraints from neutrino data within a comprehensive global framework.

Findings

Neutrino data constrains previously unbounded SMEFT operators involving tau flavor.

Including neutrino data improves constraints on NSI in the SMEFT framework.

Neutrino experiments are sensitive to new Wilson coefficient combinations, strengthening global bounds.

Abstract

We analyze how neutrino oscillation and coherent elastic neutrino-nucleus scattering data impact the global SMEFT fit. We first review the mapping between the SMEFT parameters and the so-called NSI framework, commonly considered in the neutrino literature. We also present a detailed discussion of how the measurements for the normalization of neutrino fluxes and cross sections, that will also be affected by the new physics, indirectly impact the measured oscillation probabilities. We then analyze two well-motivated simplified scenarios. Firstly, we study a lepton flavour conserving case, usually assumed in global SMEFT analyses, showing the complementarity of neutrino oscillation and CE$\nu$NS experiments with other low-energy observables. We find that the inclusion of neutrino data allows to constrain previously unbounded SMEFT operators involving the tau flavour and confirm the improvement of the constraint on a combination of Wilson coefficients previously identified. Moreover, we find that neutrino oscillation constraints on NSI are improved when embedded in the global SMEFT framework. Secondly, we study a lepton flavour violating scenario and find that neutrino data also improves over previously derived global constraints thanks to its sensitivity to new combinations of Wilson coefficients.