Kaukalons

Kaukalons are hypothetical bosons proposed in particle physics as mediators of interactions within a hidden or dark sector. They are typically assumed to be neutral under the standard model gauge group and may mix with standard model photons through kinetic mixing, or arise from an additional U(1) gauge symmetry. In this way, kaukalons can act as portals between observable matter and a secluded sector.

Models differ in details. Some describe a single kaukalon with a mass scale that can span from sub-MeV to multi-TeV ranges, while others posit a family of kaukalons with distinct masses and couplings. They are often considered in theories that extend beyond the standard model to explain phenomena such as dark matter or anomalies in precision measurements. Possible production channels include meson decays and high-energy collisions, and decay modes commonly include lepton pairs or invisible final states, depending on the coupling structure and mass.

Experimental status remains unsettled. No conclusive evidence for kaukalons has been observed to date. Searches at collider experiments, fixed-target facilities, and relevant astrophysical observations have placed upper limits on their mixing parameters, production rates, and decay signatures across broad mass ranges. These constraints guide model-building and help identify viable parameter spaces for future investigations.

See also: dark photon, hidden sector, portal interactions, physics beyond the standard model.