Consequences of DM/antiDM Oscillations for Asymmetric WIMP Dark Matter

TL;DR

This paper explores how oscillations between dark matter and anti-dark matter can re-establish annihilations, expanding the viable parameter space for asymmetric WIMP dark matter models and affecting observational constraints.

Contribution

It demonstrates that oscillations can re-open the parameter space for asymmetric dark matter, especially allowing larger WIMP masses and altering astrophysical and cosmological constraints.

Findings

Oscillations enable efficient annihilations before freeze-out.

Large WIMP masses (~100 GeV - 1 TeV) can naturally achieve correct relic abundance.

Constraints from astrophysical bodies are evaded due to re-established annihilations.

Abstract

Assuming the existence of a primordial asymmetry in the dark sector, a scenario usually dubbed Asymmetric Dark Matter (aDM), we study the effect of oscillations between dark matter and its antiparticle on the re-equilibration of the initial asymmetry before freeze-out, which enable efficient annihilations to recouple. We calculate the evolution of the DM relic abundance and show how oscillations re-open the parameter space of aDM models, in particular in the direction of allowing large (WIMP-scale) DM masses. A typical wimp with a mass at the EW scale (\sim 100 GeV - 1 TeV) presenting a primordial asymmetry of the same order as the baryon asymmetry naturally gets the correct relic abundance if the DM-number-violating Delta(DM) = 2 mass term is in the \sim meV range. The re-establishment of annihilations implies that constraints from the accumulation of aDM in astrophysical bodies are evaded. On the other hand, the ordinary bounds from BBN, CMB and indirect detection signals on annihilating DM have to be considered.