On the challenges of searching for GeV-scale long-lived particles at the LHC

Abstract

Many models of dark matter predict long-lived particles (LLPs) that can give rise to striking signatures at the LHC. Existing searches for displaced vertices are however tailored towards heavy LLPs. In this work we show that this bias severely affects their sensitivity to LLPs with masses at the GeV scale. To illustrate this point we consider two dark sector models with light LLPs that decay hadronically: a strongly-interacting dark sector with long-lived exotic mesons, and a Higgsed dark sector with a long-lived dark Higgs boson. We study the sensitivity of an existing ATLAS search for displaced vertices and missing energy in these two models and find that current track and vertex cuts result in very low efficiency for light LLPs. To close this gap in the current search programme we suggest two possible modifications of the vertex reconstruction and the analysis cuts. We calculate projected exclusion limits for these modifications and show that they greatly enhance the sensitivity to LLPs with low mass or short decay lengths.

19 pages, 9 figures; v2 matches published version

References in corpus (10)

• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• An Introduction to PYTHIA 8.2
• Echoes of a Hidden Valley at Hadron Colliders
• Probing a Secluded U(1) at B-factories
• Emerging Jets
• LHC Searches for Dark Sector Showers
• Discerning Secluded Sector gauge structures
• Theory for Baryon Number and Dark Matter at the LHC
• Invisible and displaced dark matter signatures at Belle II
• Impact of Mass Generation for Simplified Dark Matter Models