Many BSM models predict new long-lived particles (LLPs) that could be produced at the LHC and travel measurable distances before decaying. This talk will focus on a background-free search for LLPs that aims to reconstruct decay vertices inside the CMS beam pipe using charged particle tracks, along with potential future extensions to the search. In addition, this talk will also present studies of silicon pixel sensors that will be installed in the upgraded CMS tracking detector for the HL-LHC.