Pseudoscalar Mediators: A WIMP model at the Neutrino Floor

TL;DR

This paper investigates pseudoscalar mediator models for fermionic dark matter, showing that one-loop corrections can bring the scattering cross section near the neutrino floor, making detection feasible with upcoming experiments.

Contribution

It introduces a detailed analysis of one-loop contributions in pseudoscalar mediator models, highlighting their significance for direct detection prospects near the neutrino floor.

Findings

One-loop corrections dominate the scattering rate.

Certain parameter regions are within reach of future experiments.

Models can produce detectable signals near the neutrino floor.

Abstract

Due to its highly suppressed cross section (fermionic) dark matter interacting with the Standard Model via pseudoscalar mediators is expected to be essentially unobservable in direct detection experiments. We consider both a simplified model and a more realistic model based on an extended two Higgs doublet model and compute the leading one-loop contribution to the effective dark matter- nucleon interaction. This higher order correction dominates the scattering rate completely and can naturally, i.e. for couplings of order one, lead to a direct detection cross section in the vicinity of the neutrino floor. Taking the observed relic density and constraints from low-energy observables into account we analyze the direct detection prospects in detail and find regions of parameter space that are within reach of upcoming direct detection experiments such as XENONnT, LZ, and DARWIN.