Radiative corrections to light thermal pseudo-Dirac dark matter

Light thermal dark matter has emerged as an attractive theoretical possibility and a promising target for discovery at experiments in the near future. Such scenarios generically invoke mediators with very small couplings to the Standard Model, but with moderately strong couplings within the dark sector, calling into question theoretical estimates based on the lowest order of perturbation theory. As an example, we focus on a scenario in which (pseudo-)Dirac fermion dark matter is connected to the Standard Model via a dark photon charged under a new <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mi>U</a:mi><a:mo stretchy="false">(</a:mo><a:mn>1</a:mn><a:msup><a:mrow><a:mo stretchy="false">)</a:mo></a:mrow><a:mrow><a:mo>′</a:mo></a:mrow></a:msup></a:mrow></a:math> extension of the standard model, and we investigate the impact of the next-to-leading order corrections to annihilation and scattering. We find that radiative corrections can significantly impact model predictions for the relic density and scattering cross section, depending on the strength of the dark sector coupling and ratio of the dark matter to mediator mass. We also show why factorization into the yield parameter <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>Y</e:mi></e:math> typically presented in literature leads to imprecision. Our results are necessary to accurately map experimental searches into the model parameter space and assess their ability to reach thermal production targets.