Minicharges, Monopoles, and Magnetic Mixing

Minicharged particles (MCPs) arise naturally in extensions of the Standard Model with hidden sector gauge groups. Many such extensions also contain magnetic monopoles. For models containing both monopoles and MCPs, we clarify the role of the Dirac charge quantization condition in restricting the possible charges. We also show that monopoles of the hidden sector may manifest themselves as MCPs, by a generalization of the Witten effect, which we call “magnetic mixing”.