Pseudoscalar Portal Dark Matter and New Signatures of Vector-like Fermions

TL;DR

This paper investigates pseudoscalar portal dark matter models, their collider signatures involving vector-like fermions, and how current LHC data constrains these models, especially in relation to gamma ray excesses.

Contribution

It introduces simplified pseudoscalar portal dark matter models with vector-like fermions and analyzes their LHC signatures and constraints, connecting collider physics with astrophysical observations.

Findings

Certain decay channels are strongly constrained by LHC searches.

Parameter space fitting gamma ray excesses is further restricted.

Tau-rich final states remain weakly constrained.

Abstract

Fermionic dark matter interacting with the Standard Model sector through a pseudoscalar portal could evade the direct detection constraints while preserving a WIMP miracle. We study the LHC constraints on the pseudoscalar production in simplified models with the pseudoscalar either dominantly coupled to b quarks or tau leptons and explore their implications for the GeV excesses in gamma ray observations. We also investigate models with new vector-like fermions that could realize the simplified models of pseudoscalar portal dark matter. These models yield new decay channels and signatures of vector-like fermions, for instance, bbb, btautau, and tautautau resonances. Some of the signatures have already been strongly constrained by the existing LHC searches and the parameter space fitting the gamma ray excess is further restricted. On the other hand, the pure tau-rich final state is only weakly constrained so far due to the small electroweak production rate.