Particle nature of dark matter remains unknown

Determine the particle nature of dark matter, identifying the underlying particle(s) and their interactions with the Standard Model in a manner consistent with astrophysical and cosmological observations.

Background

The paper motivates feebly interacting dark matter produced via freeze-in through a spin-2 portal as a theoretically well-motivated alternative to the traditional weakly interacting massive particle paradigm. Despite extensive evidence for dark matter from cosmology and astrophysics, its particle identity and interactions remain undetermined.

By connecting early-Universe freeze-in dynamics to collider signatures at the LHC via a spin-2 mediator, the study explores experimentally testable regions of parameter space. The explicit acknowledgment that the particle nature of dark matter is still unknown frames the broader significance of probing such models.

References

While astrophysical and cosmological observations provide overwhelming evidence for the existence of DM, its particle nature is still unknown.

— Probing Freeze-In Dark Matter via a Spin-2 Portal at the LHC with Vector Boson Fusion and Machine Learning  (2604.02604 - Liu et al., 3 Apr 2026) in Section 1 (Introduction)

Despite its observational success, however, the fundamental particle nature of dark matter remains unknown, and no viable dark matter candidate has yet been conclusively detected.

— 3.5-meter Segmented-Mirror Robotic Space Telescope Mission White Paper I. Overall Architecture and Scientific Mission  (2609.02571 - Kang et al., 2 Sep 2026) in Chapter 4, Scientific Objectives, Section Cosmology, subsection Unveiling the Nature of Dark Matter