Reports

A search is presented for pair production of higgsinos, the supersymmetric partners of the Higgs bosons, in scenarios with gauge-mediated supersymmetry breaking. Each higgsino is assumed to decay into a Higgs boson and a nearly-massless gravitino. [...]

A search for new phenomena with top quark pairs in final states with one isolated lepton, either an electron or a muon, jets, and large missing transverse momentum is performed. The search is performed using the Large Hadron Collider proton--proton collision dataset at a centre-of-mass energy of $\sqrt{s}=13$ TeV recorded by the ATLAS detector and corresponding to an integrated luminosity of 140 fb$^{-1}$. [...]

Statistical combinations of searches for charginos and neutralinos using various decay channels are performed using 139fb−1 of pp collision data at √s=13TeV with the ATLAS detector at the Large Hadron Collider. Searches targeting wino-like chargino pair production, wino-like chargino-neutralino production, or higgsino production decaying via Standard Model bosons W,Z,h are combined to extend the mass reach to the produced SUSY particles by 30−100GeV. [...]

A measurement of the production of W bosons with opposite electric charges in association with two jets is presented based on $140\,\mathrm{fb}^{-1}$ of data collected by the ATLAS detector in proton-proton collisions at $\sqrt{s}=13\,\mathrm{TeV}$, during LHC Run 2. The analysis is sensitive to the scattering of W bosons, which is of particular interest in the ATLAS physics programme as it can be used to probe the electroweak symmetry breaking mechanism of the Standard Model. [...]

Measurements of the substructure of top-quark jets are presented using top quarks produced in $pp$ interactions at 13 TeV and recorded with the ATLAS detector. Top-quark jets reconstructed with the anti-$kt$ algorithm with a radius parameter $R=1.0$ are selected in top-quark pair ($t\bar{t}$) events with one top quark decaying semileptonically and the other hadronically, and in $t\bar{t}$ events where both top quarks decay hadronically. [...]

Many extensions to the Higgs sector of the Standard Model motivate additional spin-0 bosons. This search focuses on light, spin-0 bosons decaying to two photons in the 66 to 110 GeV mass range, using 140 fb−1of ppcollisions produced by the Large Hadron Collider and collected by the ATLAS detector. [...]

A search for a heavy $CP$-odd Higgs boson, $A$, decaying into a $Z$ boson and a heavy $CP$-even Higgs boson, $H$, in the $\ell\ell t\bar{t}$ and $\nu\bar{\nu}b\bar{b}$ final states is presented using the full LHC Run 2 dataset of $pp$ collisions collected with the ATLAS detector at $\sqrt{s}=13$ TeV and corresponding to an integrated luminosity of $140$~fb$^{-1}$. The search for $A\to ZH$ is performed for the first time in the $\ell\ell t\bar{t}$ and $\nu\bar{\nu}b\bar{b}$ final states and extends the reach of previous searches in different final states in the region with $m_H>350$ GeV and $m_A>800$ GeV. [...]

The production of single top quarks and top antiquarks via the $t$-channel exchange of a virtual $W$ boson are measured in proton--proton collisions at a centre-of-mass energy of 13 TeV. The full Run 2 dataset recorded with the ATLAS detector in the years 2015-2018 is used. [...]

Three searches for the direct production of staus or charginos and neutralinos in final states with at least two hadronically decaying $\tau$-leptons are presented. For chargino and neutralino production, decays via intermediate staus or Wh bosons are considered. [...]

This note describes measurements of the transverse momentum spectra of Wand Z bosons produced in proton--proton collisions at centre-of-mass energies of √s=5.02 TeV and √s=13 TeV at the LHC. Measurements are performed in the electron and muon channels, W→ℓν and Z→ℓℓ (ℓ=e or μ), and for W events further separated by charge. [...]