Searching for Elusive Dark Sectors with Terrestrial and Celestial Observations

TL;DR

This paper explores the potential existence of a light, SM-neutral dark sector coupled via portal interactions, analyzing constraints from experiments and astrophysics, and emphasizing collider bounds and future search strategies.

Contribution

It characterizes dark sectors with conformal behavior between UV and IR scales and derives experimental constraints in a model-independent framework.

Findings

High-energy colliders exclude UV scales up to a few TeV.

Constraints depend on the IR scale, with specific ranges being more constrained.

Current searches provide a baseline for designing future experiments.

Abstract

We consider the possible existence of a SM-neutral and light dark sector coupled to the visible sector through irrelevant portal interactions. Scenarios of this kind are motivated by dark matter and arise in various extensions of the Standard Model. We characterize the dark dynamics in terms of one ultraviolet scale $\Lambda_\text{UV}$, at which the exchange of heavy mediator fields generates the portal operators, and by one infrared scale $\Lambda_\text{IR}$, setting the mass gap. At energies $\Lambda_\text{IR} \ll E \ll \Lambda_\text{UV}$ the dark sector behaves like a conformal field theory and its phenomenology can be studied model independently. We derive the constraints set on this scenario by high- and low-energy laboratory experiments and by astrophysical observations. Our results are conservative and serve as a minimum requirement that must be fulfilled by the broad class of models satisfying our assumptions, of which we give several examples. The experimental constraints are derived in a manner consistent with the validity of the effective field theory used to define the portal interactions. We find that high-energy colliders give the strongest bounds and exclude UV scales up to a few TeV, but only in specific ranges of the IR scale. The picture emerging from current searches can be taken as a starting point to design a future experimental strategy with broader sensitivity.