  Soft displaced leptons are representative collider signatures of compressed
dark sectors with feeble couplings to the standard model. Prime targets are
dark matter scenarios where co-scattering or co-annihilation sets the relic
abundance upon freeze-out. At the LHC, searches for soft displaced leptons are
challenged by a large background from hadron or tau lepton decays. In this
article, we present an analysis tailored for displaced leptons with a low
transverse momentum threshold at 20 GeV. Using a neural network, we perform a
comprehensive analysis of the event kinematics, including a study of the
expected detection efficiencies and backgrounds at small momenta. Our results
show that weak-scale particles decaying into soft leptons with decay lengths
between 1mm and 1m can be probed with LHC Run 2 data. This motivates the need
for dedicated triggers that maximize the sensitivity to displaced soft leptons.

High Energy Physics - Phenomenology;High Energy Physics - Experiment