moulions
Moulions are a class of hypothetical elementary bosons proposed in discussions of hidden-sector physics. They are envisioned as gauge bosons of a proposed U(1)M symmetry that resides in a hidden sector adjacent to the standard model. In many models, moulions do not carry standard electric charge but couple to ordinary matter via a small kinetic-mixing with the photon, giving them an effective millicharge interaction with standard-model particles. They are typically assumed to have a small nonzero mass, with model-dependent ranges from sub-eV to MeV scales, and their coupling strength to visible matter is described by a dimensionless parameter ε (epsilon) that is constrained by experiments.
Theoretical role and properties: Moulions are thought to mediate a new force that can be either short-
Experimental status: There is no confirmed observation of moulions. A variety of searches—collider experiments, fixed-target setups,
Etymology and reception: The term moulion is a coined designation in theoretical discussions of hidden-sector models,