Constraints on Mirror Models of Dark Matter from Observable Neutron-Mirror Neutron Oscillation

TL;DR

This paper investigates how neutron-mirror neutron oscillation constraints impact mirror dark matter models, showing that observable oscillations require specific inflationary conditions that limit the model's parameters.

Contribution

It demonstrates the relationship between neutron-mirror neutron oscillation observability and constraints on asymmetric inflation in mirror dark matter models.

Findings

Observable oscillations require very small mass splitting and mixing parameters.

Inflation models with decay to charged particles suppress oscillations.

Weakly coupled singlet fields are necessary for observable oscillations.

Abstract

The process of neutron-mirror neutron oscillation, motivated by symmetric mirror dark matter models, is governed by two parameters: $n-n'$ mixing parameter $\delta$ and $n-n'$ mass splitting $\Delta$. For neutron mirror neutron oscillation to be observable, the splitting between their masses $\Delta$ must be small and current experiments lead to $\delta \leq 2\times 10^{-27}$ GeV and$\Delta \leq 10^{-24}$ GeV. We show that in mirror universe models where this process is observable, this small mass splitting constrains the way that one must implement asymmetric inflation to satisfy the limits of Big Bang Nucleosynthesis on the number of effective light degrees of freedom. In particular we find that if asymmetric inflation is implemented by inflaton decay to color or electroweak charged particles, the oscillation is unobservable. Also if one uses SM singlet fields for this purpose, they must be weakly coupled to the SM fields.