Speaker
Description
A search is presented for emerging jets using $140~\mathrm{fb}^{-1}$ of proton--proton collision data at $\sqrt{s} = 13~\mathrm{TeV}$, collected by the ATLAS experiment between 2015 and 2018. The search looks for the existence of a dark sector with symmetries similar to those in quantum chromodynamics. This dark sector is populated with dark quarks, which undergo showering similar to quarks in the Standard Model, leading to a high multiplicity of long-lived dark hadrons within a dark jet. These dark hadrons subsequently decay to Standard Model particles via a new heavy scalar mediating particle $\phi$. This results in jets which contain multiple displaced vertices, known as emerging jets. This analysis targets four-jet topologies, with two emerging jets and two Standard Model jets, resulting from the decay of pair-produced scalar mediators. No significant excess above the Standard Model background is observed. For dark pion proper decay lengths of $20~\mathrm{mm}$, mediator masses are excluded between $1~\mathrm{TeV}$ and $2~\mathrm{TeV}$ assuming a dark pion mass of $20~\mathrm{GeV}$.