How light can a fermion be if it has unit electric charge? We revisit the
lore that LEP robustly excludes charged fermions lighter than about 100 GeV. We
review LEP chargino searches, and find them to exclude charged fermions lighter
than 90 GeV, assuming a higgsino-like cross section. However, if the charged
fermion couples to a new scalar, destructive interference among production
channels can lower the LEP cross section by a factor of 3. In this case, we
find that charged fermions as light as 75 GeV can evade LEP bounds, while
remaining consistent with constraints from the LHC. As the LHC collects more
data, charged fermions in the 75-100 GeV mass range serve as a target for
future monojet and disappearing track searches.Comment: 35 pages, 11 figures, 2 table
