Reports

Measurements of the first three cumulants of the distribution of the event-by-event transverse momentum distribution, including the mean ⟨[\pT]⟩, variance, and skewness, are performed with the ATLAS detector at the Large Hadron Collider. These measurements are carried out for Xe+Xe collisions at √sNN=5.44 TeV with an integrated luminosity of 3 μb−1 and Pb+Pb collisions at √sNN=5.02 TeV with an integrated luminosity of 470 μb−1. [...]

This note describes a measurement of the jet radius dependence of the momentum balance between leading back-to-back dijets in 1.7~\inb\ of Pb+Pb collisions collected in 2018 and 260~\ipb\ of pp collisions collected in 2017 by the ATLAS detector at the LHC. Both data sets were collected at $\sqrtsnn =$5.02 TeV. [...]

This note presents the analysis of charged-hadron measurements in photo-nuclear collisions using 1.73 nb−1of 5.02 TeV Pb+Pb data collected in 2018 by ATLAS. Candidate photo-nuclear events are selected and background events rejected using a combination of zero degree calorimeter, pseudorapidity gap, and tracking information. [...]

This paper presents a search for hypothetical massive, charged, long-lived particles with the ATLAS detector at the LHC using an integrated luminosity of 140 fb$^{-1}$ of proton–proton collisions at $\sqrt{s}$ = 13 TeV. These particles are expected to move significantly slower than the speed of light and should be identifiable by their high transverse momenta and anomalously large specific ionisation losses dEdx in combination with low-beta measured by Time-of-Flight (ToF). [...]

A search for vector-like leptons pair-production is presented, considering their decays into a third-generation Standard Model (SM ) quark and the vector leptoquark ($U_1$) as predicted by a renormalisable and ultraviolet-complete extension of the SM, dubbed as the '4321' model. Through the assumed decay of $U_1$ into third-generation SM fermions, the final state can contain multiple tau-leptons and $b$-jets. [...]

Measurements of jet substructure are key to probing the energy frontier at colliders, and many of them use track-based observables which take advantage of the angular precision of tracking detectors. Theoretical calculations of track-based observables require ``track functions'', which characterize the transverse momentum fraction $r_q$ carried by charged hadrons from a fragmenting quark or gluon. [...]

This note presents the first study of the sensitivity of event geometry estimators to the initial state kinematics of the hard scattering in proton-lead collisions. The data used in the analysis were recorded by the ATLAS detector at a center-of-mass energy of 8.16 TeV and correspond to a luminosity of 56~nb$^{-1}$. [...]

A calibration of the ATLAS flavor-tagging algorithms using a new calibration procedure based on optimal transportation maps is presented. Simultaneous, continuous corrections to the b-, c, and light flavor classification probabilities from jet tagging algorithms in simulation are derived for b-jets using t¯t→b¯beμννevents. [...]

Neural Simulation-Based Inference (NSBI) is a powerful class of machine learning (ML)-based methods for statistical inference that naturally handles high-dimensional parameter estimation without the need to bin data into low-dimensional summary histograms. Such methods are promising for a range of measurements, including at the Large Hadron Collider (LHC), where no single observable may be optimal to scan over the entire theoretical phase space under consideration, or where binning data into histograms could result in a loss of sensitivity. [...]

A measurement of off-shell Higgs boson production in the $H^*\to ZZ\to 4\ell$ decay channel is presented. The measurement uses the 140~fb$^{-1}$ of integrated luminosity collected by the ATLAS detector during the Run 2 proton-proton collisions of the Large Hadron Collider at $\sqrt{s}=13$~TeV and supersedes our previous result in this decay channel using the same dataset. [...]