Models of new physics often predict long-lived particles that would escape current Large Hadron
Collider experiments unseen. Long-lived particles are predicted by extensions to the Standard
Model where a new sector couples to known particles via portal interactions. Such extensions
include Heavy Neutral Leptons (HNLs), axions, dark scalars and dark photons. With HNLs as
an example, we evaluate the discovery potential of the ANUBIS Experiment to a rich array of
final states. The ANUBIS setup places detector technology directly on the ATLAS cavern ceiling,
extending our lifetime reach further from the interaction point while maintaining synergy with
timing information from the main detector. Recent updates to this detector setup are showcased
in our results, including a new geometry layout and improved isolation from hadronic radiation.
Benchmark HNL models allow us to compare with other long-lived particle experiments, and
provide examples of new physics with unique discovery potential at the ANUBIS Experiment.