Reports

The expected precision of studies of Higgs-boson decays to bottom and charm quarks in associated production with a W or Z boson with the ATLAS detector at the High-Luminosity LHC are estimated, assuming a proton-proton collision dataset corresponding to 3000 fb−1 collected at a centre-of-mass energy of √s=14 TeV. The existing combined probe of these processes using a proton-proton collision dataset of 140 fb−1 at √s=13 TeV is extrapolated to High-Luminosity LHC conditions, by scaling luminosity and centre-of-mass energy, and considering several scenarios of systematic uncertainties. [...]

Weakly interacting massive particles are well motivated candidates to explain dark matter in the universe. However, the absence of clear evidence of the production of these particles at the LHC and of any direct or indirect detection impose stringent constraints on the model parameter space where this type of matter might exist. [...]

This note presents plots summarising latest ATLAS 95% confidence level exclusion lower limits on the leptoquark mass for various branching ratios into a charged lepton and a quark. Additionally, results for searches of leptoquark decaying into bτ are shown in the leptoquark coupling vs mass parameter space. [...]

This document presents projections for the top quark pole mass measurement in $t\bar t $+ 1 jet events at the High Luminosity Large Hadron Collider (HL-LHC). These projections are based on the measurement of the top quark pole mass in $t\bar t $+ 1 jet events collected with the ATLAS detector in proton–proton collisions at $\sqrt{s}=8$ TeV. [...]

Updated estimates are presented for the expected precision of measurements of the branching fractions of the rare decays of B0s→μ+μ− and B0→μ+μ− with the ATLAS detector at the HL-LHC. Projections for the effective lifetime of B0s→μ+μ− are also provided for the first time. [...]

The ATLAS and CMS experiments are unique drivers of our fundamental understanding of nature at the energy frontier. In this contribution to the update of the European Strategy for Particle Physics, we update the physics reach of these experiments at the High-Luminosity LHC (HL-LHC) in a few key areas where they will dominate the state-of-the-art for decades to come. [...]

The HL-LHC projects a leveled instantaneous proton–proton luminosity of up to $7\times10^{34}$cm$^{-2}$s$^{-1}$ with 200 simultaneous collisions within a bunch crossing (pileup) and an integrated luminosity of 3000 fb$^{-1}$. These conditions require unprecedented detector technologies in terms of radiation hardness, high detection granularity and resolution, precision track timing, and powerful triggers. [...]

This note presents projections for the study of four-top-quark production ($pp \to t\bar{t}t\bar{t}$) at the High-Luminosity LHC (HL-LHC) using a dataset of up to 3~ab$^{-1}$ at $\sqrt{s} = 14$~TeV. Two scenarios are explored to extrapolate theoretical and experimental systematic uncertainties from the current ATLAS measurement at 140~fb$^{-1}$. [...]

This note presents projections for the study of four-top-quark production ($pp \to t\bar{t}t\bar{t}$) at the High-Luminosity LHC (HL-LHC) using a dataset of up to 3~ab$^{-1}$ at $\sqrt{s} = 14$~TeV. Two scenarios are explored to extrapolate theoretical and experimental systematic uncertainties from the current ATLAS measurement at 140~fb$^{-1}$. [...]

To achieve its physics program, the ATLAS collaboration operates large, internationally-distributed computing systems and maintains millions of lines of code. These systems and software are growing in complexity in preparation for the High Luminosity upgrade of the LHC. [...]