A muon jet ($\mu$-jet) is a very special feature that consists of a cluster of collimated muons from the decay of a fast-moving light particle of mass about $\mathcal{O}(1\mathrm{GeV})$. We will use this feature to search for very light particles from rare decays of the Higgs boson. For such a small angular separation of muons which might come from a long-lived particle, both ATLAS and CMS could have the displaced-vertexing-reconstruction capability. We use two simple models of the Higgs portal type to explore the possibilities of event topologies with two $2\mu$-jets, one $2\mu$-jet and one $4\mu$-jet, and two $4\mu$-jets in the final state at LHC-14. We also summarize existing constraints on these models.

• Received 21 October 2016

DOI:https://doi.org/10.1103/PhysRevD.95.035012