Updated Bounds on Milli-Charged Particles

Abstract

We update the bounds on fermions with electric charge $εe$ and mass $m_ε$. For $m_ε\lsim m_e$ we find $10^{-15}\lsimε<1$ is excluded by laboratory experiments, astrophysics and cosmology. For larger masses, the limits are less restrictive and depend on $m_ε$. For milli-charged neutrinos, the limits are stronger, especially if the different flavors mix as suggested by current experimental evidence.