Light long-lived particles at the LHC and at Belle II
Elias Bernreuther (Fermilab)

Searches for long-lived particles (LLPs) are a rapidly expanding
frontier at the LHC and other collider experiments. Still, many gaps
remain in the current search program, in particular for LLPs with masses
at the GeV or sub-GeV scale and with very large decay lengths. In this
talk, I will illustrate two different approaches to filling this gap by
discussing two models of light LLPs and their associated collider
signals. First, I will show that the dominant decay mode of vectorlike
leptons can be a very long-lived pseudoscalar and a tau lepton and argue
that the muon chambers of CMS or ATLAS are ideal places to search for
this final state. Second, I will illustrate the excellent sensitivity of
Belle II to light LLPs with meter-scale decay lengths using the example
of displaced vertex signals from strongly interacting dark sectors.