Leptons lurking in semi-visible jets at the LHC

TL;DR

This paper proposes a novel search strategy at the LHC for semi-visible jets originating from confining dark sectors, focusing on non-isolated lepton pairs within jets to detect potential dark matter signatures.

Contribution

It introduces a model-independent search method for semi-visible jets with leptonic signatures, enhancing detection sensitivity for dark sector particles at the LHC.

Findings

Potential to observe 3σ evidence of mediators up to 3.5 TeV.

Exclusion limits extend to 4.5 TeV for certain models.

Lepton pair invariant mass analysis can reach 5σ discovery at 3.5 TeV.

Abstract

This Letter proposes a new search for confining dark sectors at the Large Hadron Collider. As a result of the strong dynamics in the hidden sector, dark matter could manifest in proton-proton collisions at the Large Hadron Collider in form of hadronic jets containing stable invisible bound states. These semi-visible jets have been studied theoretically and experimentally in the fully hadronic signature where the unstable composite dark matter can only decay promptly back to Standard Model quarks. We present a simplified model based on two messenger fields separated by a large mass gap allowing dark bound states to decay into pairs of oppositely charged leptons. The resulting experimental signature is characterized by non-isolated lepton pairs inside semi-visible jets. We propose a search strategy independent from the underlying model assumptions targeting this new signature, and discuss the orthogonality with respect to the existing searches. Remaining agnostic on the shape of the di-lepton spectrum, we determine the sensitivity of a dedicated analysis to the target signal. The proposed search can claim the 3{\sigma} evidence (exclusion) of the heavier mediator up to masses of 3.5 TeV (4.5 TeV) with the full Run 2 data of the LHC. Exploiting the resonant feature of the lepton pairs can enhance the sensitivity reach on a specific model. We estimate that an analysis using the di-lepton invariant mass information can reach 5{\sigma} discovery up to masses of 3.5 TeV and improve the exclusion up to more than 5 TeV.