Flavour-dependent radiative correction to neutrino-neutrino refraction

TL;DR

This paper calculates flavor-dependent radiative corrections to neutrino-neutrino refraction within the Standard Model, highlighting the dominant loop-level effects involving tau leptons and their impact on neutrino flavor evolution in dense environments.

Contribution

It provides the first detailed calculation of flavor non-universal corrections to neutrino refraction, emphasizing the role of tau leptons and their influence on collective neutrino oscillations.

Findings

Loop-level corrections involve tau leptons and dominate the refractive difference.

Corrections significantly affect flavor evolution in dense neutrino gases.

Explicit formulation of non-universal neutrino-neutrino interactions in oscillation equations.

Abstract

In the framework of the Standard Model we calculate the flavour non-universal correction for neutrino refraction in a neutrino background and verify a similar previous result for the case of ordinary-matter background. The dominant term arises at loop level and involves tau leptons circulating in the loop. These O(G_F m_tau^2) corrections to the tree-level potential provide the dominant refractive difference between nu_mu and nu_tau unless the medium contains mu or tau leptons. Our results affect the flavour evolution of dense neutrino gases and may be of interest for collective three-flavour oscillations of supernova neutrinos. We spell out explicitly how these non-universal neutrino-neutrino interactions enter the flavour oscillation equations.