Minimal Asymmetric Dark Matter

TL;DR

This paper explores the viability of minimal asymmetric dark matter candidates within an $SU(2)_L$ multiplet framework, considering chemical equilibrium conditions and experimental detection constraints, and identifies specific hypercharge and mass ranges for potential candidates.

Contribution

It introduces a minimal model for asymmetric dark matter involving a single $SU(2)_L$ multiplet and analyzes the constraints from direct detection experiments.

Findings

Scalar or fermion multiplets with hypercharge y=1 are the only viable candidates.

Preferred candidates are quintuplets or larger $SU(2)$ representations.

Masses of these candidates are constrained to a few TeV.

Abstract

In the early Universe, any particle carrying a conserved quantum number and in chemical equilibrium with the thermal bath will unavoidably inherit a particle-antiparticle asymmetry. A new particle of this type, if stable, would represent a candidate for asymmetric dark matter (DM) with an asymmetry directly related to the baryon asymmetry. We study this possibility for a minimal DM sector constituted by just one (generic) $SU(2)_L$ multiplet $\chi$ carrying hypercharge, assuming that at temperatures above the electroweak phase transition an effective operator enforces chemical equilibrium between $\chi$ and the Higgs boson. We argue that limits from DM direct detection searches severely constrain this scenario, leaving as the only possibilities scalar or fermion multiplets with hypercharge $y = 1$, preferentially quintuplets or larger $SU(2)$ representations, and with a mass in the few TeV range.