Core Concepts
This paper investigates the production of sub-GeV millicharge dark matter particles through the freeze-in mechanism within a U(1)X hidden sector, emphasizing the crucial role of hidden sector temperature evolution and clarifying common misunderstandings about millicharge generation.
Stats
The dark photon can contribute at most ~5% to the total observed dark matter relic density.
The lifetime of the dark photon is roughly 10^18 seconds.
Quotes
"The connection between kinetic mixing and the millicharge can be traced back to [28,29]."
"It has been shown that pure kinetic mixing between an extra U(1) and the hypercharge gauge field cannot generate a millicharge [31]."
"The millicharge carried by the U(1)X dark fermions can be obtained from: (1) The dark particle carries a tiny amount of hypercharge as a prior. (2) A kinetic mixing between a massless U(1) and the hypercharge gauge field, and the generated millicharge is proportional to the kinetic mixing parameter. (3) The mass mixing between a massive U(1) with the hypercharge gauge field [31, 32]."