Search for emerging jets in $pp$ collisions at $\sqrt{s} = 13.6$ TeV with the ATLAS experiment

TL;DR

This paper reports a search for emerging jets from a dark sector in proton-proton collisions at 13.6 TeV using ATLAS data, setting new constraints on dark sector models with long-lived dark mesons and mediators.

Contribution

It presents the first direct constraints on emerging jet pair production via a Z' mediator and the first search for emerging jets via t-channel scalar mediator exchange.

Findings

No significant excess over Standard Model background observed.

Excluded Z' mediator masses between 600 and 2550 GeV for certain couplings.

Excluded scalar mediator masses between 600 and 1375 GeV for specific parameters.

Abstract

A search for emerging jets is presented using 51.8 fb$^{-1}$ of proton-proton collision data at $\sqrt{s} = 13.6$ TeV, collected by the ATLAS experiment during 2022 and 2023. The search explores a hypothetical dark sector featuring 'dark quarks', which are charged under a confining gauge group and couple to the Standard Model via a new mediator particle. These dark quarks undergo showering and hadronization within the dark sector, forming long-lived dark mesons that decay back into Standard Model particles. This results in jets which contain multiple displaced vertices known as emerging jets. The analysis targets events with pairs of emerging jets, produced either through a vector mediator, $Z'$, in the $s$-channel, or a scalar mediator, $\Phi$, in the $t$-channel. No significant excess over the Standard Model background is observed. Assuming a dark pion proper decay length between 5 and 50 mm, $Z'$ mediator masses between 600 and 2550 GeV are excluded for quark and dark quark coupling values of 0.01 and 0.1, respectively. For a quark-dark quark coupling of $0.1$, $\Phi$ mediator masses between 600 and 1375 GeV are excluded. These results provide the first direct constraints on emerging jet pair production via a $Z'$ mediator, and represent the first search to investigate emerging jet production via $t$-channel exchange of a scalar mediator.