millicharged
Millicharged refers to hypothetical particles that carry an electric charge much smaller than the elementary charge e. In many models, their charge is q = ε e, with ε ≪ 1. Millicharged particles are not part of the Standard Model, but can arise in theories that extend it by introducing hidden-sector states that interact weakly with ordinary matter through electromagnetism.
The most common theoretical origin is kinetic mixing between a hidden U(1) gauge field and the Standard
Phenomenology includes electromagnetic interactions that produce ionization and energy loss in detectors proportional to ε^2, and
Constraints and searches are broad. Cosmological and astrophysical data generally impose strong limits on ε for many