Search for pair production of third-generation scalar leptoquarks decaying into a top quark and a $\tau$-lepton in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

Abstract

A search for pair production of third-generation scalar leptoquarks decaying into a top quark and a $\tau$-lepton is presented. The search is based on a dataset of $pp$ collisions at $\sqrt{s}=13$ TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb${}^{-1}$. Events are selected if they have one light lepton (electron or muon) and at least one hadronically decaying $\tau$-lepton, or at least two light leptons. In addition, two or more jets, at least one of which must be identified as containing $b$-hadrons, are required. Six final states, defined by the multiplicity and flavour of lepton candidates, are considered in the analysis. Each of them is split into multiple event categories to simultaneously search for the signal and constrain several leading backgrounds. The signal-rich event categories require at least one hadronically decaying $\tau$-lepton candidate and exploit the presence of energetic final-state objects, which is characteristic of signal events. No significant excess above the Standard Model expectation is observed in any of the considered event categories, and 95% CL upper limits are set on the production cross section as a function of the leptoquark mass, for different assumptions about the branching fractions into $t\tau$ and $b\nu$. Scalar leptoquarks decaying exclusively into $t\tau$ are excluded up to masses of 1.43 TeV while, for a branching fraction of 50% into $t\tau$, the lower mass limit is 1.22 TeV.

59 pages in total, author list starting page 43, 15 figures, 10 tables, submitted to JHEP. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2019-15/

References in corpus (28)

• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• Event generation with SHERPA 1.1
• Herwig++ Physics and Manual
• Parton distributions in the LHC era: MMHT 2014 PDFs
• A parton shower algorithm based on Catani-Seymour dipole factorisation
• 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
• The Catchment Area of Jets
• 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
• B-physics anomalies: a guide to combined explanations
• Jet energy scale and resolution measured in proton-proton collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Performance of the ATLAS muon triggers in Run 2
• $R_K$ and future $b\to s\ell \ell$ BSM opportunities
• Higgs boson production in association with top quarks in the POWHEG BOX
• QCD NLO and EW NLO corrections to $t\bar{t}H$ production with top quark decays at hadron collider
• NNLL-fast: predictions for coloured supersymmetric particle production at the LHC with threshold and Coulomb resummation
• What is the scale of new physics behind the $B$-flavour anomalies?
• Weak corrections to Higgs hadroproduction in association with a top-quark pair
• Identification and energy calibration of hadronically decaying tau leptons with the ATLAS experiment in $pp$ collisions at $\sqrt{s}$=8 TeV
• Measurement of the $t\bar{t}Z$ and $t\bar{t}W$ cross sections in proton-proton collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Search for pairs of scalar leptoquarks decaying into quarks and electrons or muons in $\sqrt{s}=13$ TeV pp collisions with the ATLAS detector
• Evidence for $t\bar{t}t\bar{t}$ production in the multilepton final state in proton-proton collisions at $\sqrt{s}$=13 TeV with the ATLAS detector
• Precision predictions for scalar leptoquark pair-production at hadron colliders
• $B$ decay anomalies and dark matter from vectorlike confinement
• Search for pair production of scalar leptoquarks decaying into first- or second-generation leptons and top quarks in proton-proton collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

Cited by in corpus (29)

• On the single leptoquark solutions to the $B$-physics anomalies
• Searching for Leptoquarks at Future Muon Colliders
• Inclusive nonresonant multilepton probes of new phenomena at $\sqrt{s}=$ 13 TeV
• Impact of $B\to K\nu \bar{\nu }$ measurements on beyond the Standard Model theories
• Search for pair production of scalar leptoquarks decaying into first- or second-generation leptons and top quarks in proton-proton collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector
• Exploration at the high-energy frontier: ATLAS Run~2 searches investigating the exotic jungle beyond the Standard Model
• Global fit to $b\to c\tau \nu$ anomalies as of Spring 2024
• Search for new phenomena in $pp$ collisions in final states with tau leptons, $b$-jets, and missing transverse momentum with the ATLAS detector
• Distinguishing signatures of scalar leptoquarks at hadron and muon colliders
• Improving third-generation leptoquark searches with combined signals and boosted top
• Leptoquark-vectorlike quark model for the CDF $m_W$, $(g-2{)}_{\mu }$, $R_{K^{(\ast )}}$ anomalies and neutrino mass
• A model for the Singlet-Triplet Leptoquarks
• Phenomenology of Scalar Leptoquarks at the LHC in Explaining the Radiative Neutrino Mass, Muon $g-2$ and Lepton Flavour Violating Observables
• Search for pair production of third-generation leptoquarks decaying into a bottom quark and a $\tau$-lepton with the ATLAS detector
• Constraints on leptoquarks from lepton-flavour-violating tau-lepton processes
• Marriage between neutrino mass and flavor anomalies
• Collider Signatures of a Scalar Leptoquark and Vector-like Lepton in Light of Muon Anomaly
• Leptoquark and vector-like quark extended models as the explanation of the muon $g-2$ anomaly
• Leptoquarks, axions and the unification of B, L, and Peccei-Quinn symmetries
• Gravitational wave signals from leptoquark-induced first order electroweak phase transitions
• Leptonic signatures of color-sextet scalars
• Mutually elusive: vectorlike antileptons and leptoquarks
• Search for leptoquark pair production decaying into $t{e}^{-}\bar{t}{e}^{+}$ or $t{\mu }^{-}\bar{t}{\mu }^{+}$ in multi-lepton final states in $pp$ collisions at 13 TeV with the ATLAS detector
• Search for scalar leptoquarks produced via $\tau$-lepton-quark scattering in pp collisions at $\sqrt{s}$ = 13 TeV
• A search for $R$-parity violating supersymmetric decays of the top squark to a $b$-jet and a lepton in $\sqrt{s}$ = 13 TeV $pp$ collisions with the ATLAS detector
• Constraining electroweak and strongly charged long-lived particles with CheckMATE
• Phenomenological study of a gauged $L_{\mu }-L_{\tau }$ model with a scalar leptoquark
• Constraining the new contributions to electron $g-2$ in a radiative neutrino mass model
• Constraining Scalar Doublet and Triplet Leptoquarks with Vacuum Stability and Perturbativity