Neutrino Non-Standard Interactions via Light Scalars in the Earth, Sun, Supernovae and the Early Universe

TL;DR

This paper investigates how ultra-light scalar mediators could induce medium-dependent neutrino masses, affecting oscillations in various environments, and explores the potential for observing these effects in future astrophysical and cosmological data.

Contribution

It derives general expressions for scalar NSI using quantum field theory at finite density and temperature, and analyzes constraints and observability in different media and experiments.

Findings

Observable scalar NSI effects are unlikely in current terrestrial experiments.

Future solar and supernova neutrino observations could detect scalar NSI effects.

Cosmological data may provide indirect evidence for scalar NSI.

Abstract

Non-standard interactions (NSI) of neutrinos with matter mediated by a scalar field would induce medium-dependent neutrino masses which can modify oscillation probabilities. Generating observable effects requires an ultra-light scalar mediator. We derive general expressions for the scalar NSI using techniques of quantum field theory at finite density and temperature, including the long-range force effects, and discuss various limiting cases applicable to the neutrino propagation in different media, such as the Earth, Sun, supernovae and early Universe. We also analyze various terrestrial and space-based experimental constraints, as well as astrophysical and cosmological constraints on these NSI parameters, applicable to either Dirac or Majorana neutrinos. By combining all these constraints, we show that observable scalar NSI effects, although precluded in terrestrial experiments, are still possible in future solar and supernovae neutrino data, and in cosmological observations such as cosmic microwave background and big bang nucleosynthesis data.