Cosmic Four-Fermion Neutrino Secret Interactions, Enhancement and Total Cross Section

TL;DR

This paper investigates how hypothetical short-range secret interactions between neutrinos can significantly alter their scattering cross sections and densities, with potential implications for neutrino physics and cosmology.

Contribution

It introduces a generic model for low-energy neutrino interactions using a delta potential and analyzes the effects of these secret interactions on scattering and enhancement phenomena.

Findings

Repulsive potentials decrease total cross section and increase neutrino density.

Attractive potentials can cause substantial Sommerfeld enhancement.

The model links phenomenological parameters to observable scattering effects.

Abstract

The scattering of neutrinos assuming a "secret" interaction at low energy is considered. To leading order in energy, the two-body potential is a $\delta$-potential, and it is used as a motivation to study generic short-range elastic interactions between neutrinos. The scattering cross section and Sommerfeld enhancement depend on two phenomenological parameters deriving from the exact form of the potential, akin to "renormalized" coupling constants. Repulsive potentials lead to a decrease in the total cross section, resulting in an enhancement of the neutrino density. For attractive potentials of the right form, substantial Sommerfeld enhancement can appear.