Publications database

This note presents a study of the ATLAS Monte Carlo (MC) sample describing $pp \to b \bar{b} \ell^+ \ell^- \nu_{\ell} \bar{\nu}_{\ell}$ events at next-to-leading order in quantum chromodynamics. Events are generated using the $\text{Powheg Box Res}$ implementation of the $bb4\ell$ process and are interfaced with $\text{Pythia 8}$ for parton showering and hadronization. [...]

Measurements of the rapidity asymmetry in top-quark pair production and the energy asymmetry in the top-quark pair production associated with an energetic jet provide information on effective field theory parameters. A combination of the rapidity asymmetry and energy asymmetry measurements is performed, taking the correlations between the systematic uncertainties and the statistical correlations due to overlapping events into account. [...]

Projected sensitivity for $t$-channel vector leptoquark in final states with $b$-jets, and single-production vector-like $T$ quark (VLT) decaying to $W(\ell \nu)b$, using the ATLAS experiment at the High Luminosity LHC (HL-LHC) is presented: obtained from the extrapolation of analyses from the Run~2 dataset, using 140~$\mathrm{fb^{-1}}$ of data at $\sqrt{s} = 13$~TeV. Two scenarios for the systematic uncertainties are taken into account. [...]

Many promising beyond the Standard Model (BSM) theories predict invisible long-lived particles (LLPs) that travel macroscopic distances before decaying into visible Standard Model (SM) particles with a common spatial origin. Fast and accurate reconstruction of secondary vertices therefore plays a central role in ATLAS LLP searches [...]

This work presents a novel application of machine learning to the pattern-recognition stage of charged-particle reconstruction, enabling learned hit-to-track association within dense environments, such as the cores of high-pTjets. Our Transformer-based architecture is based on a MaskFormer model that jointly optimises hit assignments and the estimation of the charged particles' properties [...]

As part of the ATLAS TDAQ Phase-II upgrade project, the Event Filter Tracking system will allow online tracking for the trigger of the ATLAS experiment in the HL-LHC era. While the system is still under design, this note presents an overview of how FPGA accelerators are envisioned to be potentially used for online track reconstruction [...]

The HL-LHC upgrade of the ATLAS inner detector (ITk) brings an unprecedented challenge, both in terms of the large number of silicon cluster readouts and the throughput required for budget-constrained track reconstruction. Applying Graph Neural Networks (GNNs) has been shown to be a promising solution to this problem with competitive physics performance at sub-second inference time [...]

The Event Filter (EF) Tracking system allows real-time, online tracking for the ATLAS trigger in the upcoming HL-LHC era. Although still under development, this note highlights the impressive performance achieved so far by integrating GPU accelerators into the tracking workflow [...]

Uncertainties in the predictions of general-purpose Monte-Carlo event generators, particularly those related to parton showering or hadronisation and other non-perturbative effects, are a leading source of systematic uncertainty in many ATLAS analyses. These modelling uncertainties are often estimated using a two-point approach, where the difference between two generators that use different models for these effects is used as the uncertainty. [...]

Assuming Galactic cosmic rays originate in supernovae and the winds of massive stars, starburst galaxies should produce very-high-energy (VHE; E > 100 GeV) gamma-ray emission via the interaction of their copious quantities of cosmic rays with the large reservoirs of dense gas within the galaxies. Such VHE emission was detected by VERITAS from the starburst galaxy M82 in 2008–09. [...]