Uncovering tau leptons-enriched semi-visible jets at the LHC

• Published in: The European physical journal. C, Particles and fields Particles and fields, 2023-07, Vol.83 (7), p.599-10, Article 599
• Main Authors: Beauchesne, Hugues, Cazzaniga, Cesare, de Cosa, Annapaola, Doglioni, Caterina, Fitschen, Tobias, di Cortona, Giovanni Grilli, Zhou, Ziyuan
• Format: Article
• Language: English
• Subjects: Analysis; Astronomy; Astrophysics and Cosmology; Collisions (Nuclear physics); Constraint modelling; Elementary Particles; Hadrons; Heavy Ions; Jets; Large Hadron Collider; Leptons; Letter; Measurement Science and Instrumentation; Nuclear Energy; Nuclear Physics; Particle accelerators; Physics; Physics and Astronomy; Protons; Quantum chromodynamics; Quantum Field Theories; Quantum Field Theory; Quarks; Solenoids; Standard model (particle physics); String Theory; Topology
• ISSN: 1434-6044; 1434-6052; 1434-6052
• DOI: 10.1140/epjc/s10052-023-11775-6

This Letter proposes a new signature for confining dark sectors at the Large Hadron Collider. Under the assumption of a QCD-like hidden sector, hadronic jets containing stable dark bound states could manifest in proton-proton collisions. We present a simplified model with a Z ′ boson yielding the production of jets made up of dark bound states and subsequently leading to the decays of those that are unstable to τ leptons and Standard Model quarks. The resulting signature is characterised by non-isolated τ lepton pairs inside semi-visible jets. We estimate the constraints on our model from existing CMS and ATLAS analyses. We propose a set of variables that leverage the leptonic content of the jet and exploit them in a supervised jet tagger to enhance the signal-to-background separation. Furthermore, we discuss the performance and limitations of current triggers for accessing sub-TeV Z ′ masses, as well as possible strategies that can be adopted by experiments to access such low mass regions. We estimate that with the currently available triggers, a high mass search can claim a 5 σ discovery (exclusion) of the Z ′ boson with a mass up to 4.5 TeV (5.5 TeV) with the full Run 2 data of the LHC when the fraction of unstable dark hadrons decaying to τ lepton pairs is around 50 % , and with a coupling of the Z ′ to right-handed up-type quarks of 0.25. Furthermore, we show that, with new trigger strategies for Run 3, it may be possible to access Z ′ masses down to 700 GeV, for which the event topology is still composed of two resolved semi-visible jets.