Multi-track Displaced Vertices at B-Factories

We propose a program of inclusive, multi-track displaced vertex searches at B-factories, which are expected to be low background and sensitive to a wide variety of hidden sector models. Multi-particle hidden sectors often include long-lived particles (LLPs) which result from approximate symmetries. We use an effective field theory framework to classify the decays of GeV-scale LLPs, finding that, generically, LLPs can decay to more than two charged particles. This allows us to investigate the sensitivity of searches for different numbers of displaced vertices per event and track requirements per displaced vertex for several LLP-production modes, including dark photons and dark Higgs bosons. We show that our proposed program of inclusive searches offers sensitivity to a large range of hidden sector models that are otherwise unconstrained by current or planned searches.