Updated Bounds on Milli-Charged Particles

Abstract

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