Search for dark matter produced in association with a single top quark and an energetic $W$ boson in $\sqrt{s}=$ 13 TeV $pp$ collisions with the ATLAS detector

Abstract

This paper presents a search for dark matter, $\chi$, using events with a single top quark and an energetic $W$ boson. The analysis is based on proton-proton collision data collected with the ATLAS experiment at $\sqrt{s}=$ 13 TeV during LHC Run 2 (2015-2018), corresponding to an integrated luminosity of 139 fb${}^{-1}$. The search considers final states with zero or one charged lepton (electron or muon), at least one $b$-jet and large missing transverse momentum. In addition, a result from a previous search considering two-charged-lepton final states is included in the interpretation of the results. The data are found to be in good agreement with the Standard Model predictions and the results are interpreted in terms of 95% confidence-level exclusion limits in the context of a class of dark matter models involving an extended two-Higgs-doublet sector together with a pseudoscalar mediator particle. The search is particularly sensitive to on-shell production of the charged Higgs boson state, $H^{\pm }$, arising from the two-Higgs-doublet mixing, and its semi-invisible decays via the mediator particle, $a$: $H^{\pm }\to W^{\pm }a(\to \chi \chi )$. Signal models with $H^{\pm }$ masses up to 1.5 TeV and $a$ masses up to 350 GeV are excluded assuming a tan$\beta$ value of 1. For masses of $a$ of 150 (250) GeV, tan$\beta$ values up to 2 are excluded for $H^{\pm }$ masses between 200 (400) GeV and 1.5 TeV. Signals with tan$\beta$ values between 20 and 30 are excluded for $H^{\pm }$ masses between 500 and 800 GeV.

58 pages in total, author list starting page 41, 10 figures, 9 tables, published in Eur. Phys. J. C. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2021-01/

References in corpus (27)

• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• An Introduction to PYTHIA 8.2
• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• Event generation with SHERPA 1.1
• Herwig++ Physics and Manual
• A parton shower algorithm based on Catani-Seymour dipole factorisation
• Vector boson production at hadron colliders: a fully exclusive QCD calculation at NNLO
• Single-top Wt-channel production matched with parton showers using the POWHEG method
• Two-loop soft anomalous dimensions for single top quark associated production with a W- or H-
• Automatic spin-entangled decays of heavy resonances in Monte Carlo simulations
• Single-top hadroproduction in association with a W boson
• Next-to-next-to-leading-order collinear and soft gluon corrections for t-channel single top quark production
• NNLL resummation for s-channel single top quark production
• HistFitter software framework for statistical data analysis
• Scalar Simplified Models for Dark Matter
• A Renormalizable Model for the Galactic Center Gamma Ray Excess from Dark Matter Annihilation
• Power Counting to Better Jet Observables
• Constraints on mediator-based dark matter and scalar dark energy models using $\sqrt{s}=13$ TeV $pp$ collision data collected by the ATLAS detector
• Self-consistent Dark Matter Simplified Models with an s-channel scalar mediator
• The Top Window for dark matter
• Determining the CP nature of spin-0 mediators in associated production of dark matter and $t\bar{t}$ pairs
• Search for new phenomena in events with two opposite-charge leptons, jets and missing transverse momentum in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Search for dark matter produced in association with a Standard Model Higgs boson decaying into $b$-quarks using the full Run 2 dataset from the ATLAS detector
• Search for dark matter in events with missing transverse momentum and a Higgs boson decaying into two photons in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Two Higgs Doublet Dark Matter Portal
• Search for dark matter produced in association with a single top quark or a top quark pair in proton-proton collisions at $\sqrt{s}=$ 13 TeV
• The THDMa revisited

Cited by in corpus (3)

• Exploration at the high-energy frontier: ATLAS Run~2 searches investigating the exotic jungle beyond the Standard Model
• Combination and summary of ATLAS dark matter searches interpreted in a 2HDM with a pseudo-scalar mediator using 139 fb${}^{-1}$ of $\sqrt{s}=13$ TeV $pp$ collision data
• Measurement of jet substructure in boosted $t\bar{t}$ events with the ATLAS detector using 140 fb${}^{-1}$ of 13 TeV $pp$ collisions