  For years, it has been believed that the main LHC detectors can only
restrictively play the role of a lifetime frontier experiment exploring the
parameter space of long-lived particles (LLPs) - hypothetical particles with
tiny couplings to the Standard Model. This paper demonstrates that the LHCb
experiment may become a powerful lifetime frontier experiment if it uses the
new Downstream algorithm reconstructing tracks that do not let hits in the LHCb
vertex tracker. In particular, for many LLP scenarios, LHCb may be as sensitive
as the proposed experiments beyond main LHC detectors for various LLP models,
including heavy neutral leptons, dark scalars, dark photons, and axion-like
particles.
