Cosmological radiation density with non-standard neutrino-electron interactions

TL;DR

This paper investigates how non-standard neutrino-electron interactions influence neutrino decoupling in the early universe and their effect on the effective number of neutrinos, $N_{eff}$, comparing cosmological and terrestrial constraints.

Contribution

It analyzes the impact of non-universal and flavor-changing NSI on neutrino decoupling and $N_{eff}$, highlighting degeneracies and the complementarity of cosmological and terrestrial data.

Findings

NSI can significantly alter $N_{eff}$ predictions.

Future cosmological surveys can improve constraints on NSI.

Degeneracies exist between NSI parameters and standard neutrino physics.

Abstract

Non-standard interactions (NSI) between neutrinos and electrons can significantly modify the decoupling of neutrinos from the plasma. These interactions have two effects on the overall picture: (i) they alter neutrino oscillations though matter effects and (ii) they modify the scattering and annihilation processes involving neutrinos and electrons and positrons. We study the role of non-universal and flavour-changing NSI in the decoupling and how they impact the determination of the effective number of neutrinos, $N_{eff}$. We examine the degeneracies between NSI parameters and we compare the expected sensitivity from future cosmological surveys with the current limits from terrestrial experiments. We outline the complementarity between both approaches.