Cosmological radiation density with non-standard neutrino-electron interactions

Pablo Martínez-Miravé

doi:10.1088/1742-6596/2156/1/012011

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.

Highlights

The current data from solar, atmospheric, reactor and accelerator neutrino experiments are well explained by the existence of flavour oscillations in the framework of three-neutrino mixing
We have addressed the impact of neutrino non-standard interactions with electrons on their decoupling from the primordial plasma
Out of the two main effects caused by non-standard interactions (NSI), namely the modifications to flavour oscillations in the dense quantum electrodynamics (QED) medium and their contribution to scattering and annihilation processes between electrons and neutrinos, we have shown that the latter dominates

Summary

Introduction

The current data from solar, atmospheric, reactor and accelerator neutrino experiments are well explained by the existence of flavour oscillations in the framework of three-neutrino mixing (see e.g. [1]). Non-zero NSI could affect astrophysical and cosmological scenarios involving neutrinos We consider their implications on the decoupling process of neutrinos in the early universe, as noted in [3, 4]. It is well known that weak interactions keeping neutrinos in equilibrium with the primeval plasma become ineffective at a temperature of O(MeV) and these elusive particles decouple, constituting the cosmological neutrino background. This process is nowadays well understood, and the percent deviations of the neutrino. We discuss how future cosmological measurements of Neff can be used as a complementary way to constrain these exotic scenarios

Neutrino non-standard interactions with electrons

Current bounds on NSI with electrons

Impact of non-standard interactions on Neff

Conclusions