Abstract: The ATLAS Google Project was established as part of an ongoing evaluation of the use of commercial clouds by the ATLAS Collaboration, in anticipation of the potential future adoption of such resources by WLCG grid sites to fulfil or complement their computing pledges. Seamless integration of Google cloud resources into the worldwide ATLAS distributed computing infrastructure was achieved at large scale and for an extended period of time, and hence cloud resources are shown to be an effective mechanism to provide additional, flexible computing capacity to ATLAS. For the first time a total cost of ownership analysis has been performed, to identify the dominant cost drivers and explore effective mechanisms for cost control. Network usage significantly impacts the costs of certain ATLAS workflows, underscoring the importance of implementing such mechanisms. Resource bursting has been successfully demonstrated, whilst exposing the true cost of this type of activity. A follow-up to the project is underway to investigate methods for improving the integration of cloud resources in data-intensive distributed computing environments and reducing costs related to network connectivity, which represents the primary expense when extensively utilising cloud resources.
Transition metal dichalcogenides have been attracting extensive attention as effective piezocatalysts for a wide range of applications, in particular, environmental remediation. Herein, WS2 nanoflowers with 2H-rich ultrathin petals are prepared by rapid synthesis based on magnetic induction heating (MIH) of sodium tungstate and thiourea, and the 2H phase is further enriched by Fe doping, in contrast to conventional pyrolysis that produces largely 1 T phase. Among the series, the sample prepared at 400 A for 10 s with an iron loading of ca. 0.1 wt% (3-Fe/WS2-400) exhibits the strongest piezoelectric response and greatest catalytic activity towards the selective reduction of oxygen to hydrogen peroxide under ultrasonic irradiation, reaching an ultrahigh H2O2 generation rate of 4.68 mM g⁻¹ h⁻¹, over 47 times higher than that of bulk-like WS₂. This is due to enhanced adsorption of O2 and manipulation of the electronic band structure by Fe doping that becomes favorable for oxygen reduction to H2O2, as manifested in theoretical studies based on density functional theory calculations. This unique property can be exploited for environmental remediation, as exemplified in the effective degradation of a range of organic pollutants. Results from this study highlight the unique potential of MIH in the structural engineering of functional nanomaterials for sustainable energy technologies.
A search for the production of three massive vector bosons, VVZ(V=W,Z), in proton–proton collisions at s=13 TeV is performed using data with an integrated luminosity of 140 fb−1 recorded by the ATLAS detector at the Large Hadron Collider. Events produced in the leptonic final states WWZ→ℓνℓνℓℓ (ℓ=e,μ), WZZ→ℓνℓℓℓℓ, ZZZ→ℓℓℓℓℓℓ, and the semileptonic final states WWZ→qqℓνℓℓ and WZZ→ℓνqqℓℓ, are analysed. The measured cross section for the pp→VVZ process is 660−90+93(stat.)−81+88(syst.) fb, and the observed (expected) significance is 6.4 (4.7) standard deviations, representing the observation of VVZ production. In addition, the measured cross section for the pp→WWZ process is 442±94(stat.)−52+60(syst.) fb, and the observed (expected) significance is 4.4 (3.6) standard deviations, representing evidence of WWZ production. The measured cross sections are consistent with the Standard Model predictions. Constraints on physics beyond the Standard Model are also derived in the effective field theory framework by setting limits on Wilson coefficients for dimension-8 operators describing anomalous quartic gauge boson couplings.
Computerized microscopes improve repeatability, throughput, antisepsis, data analysis and data sharing in the biological laboratory, but these machines are cost-prohibitive in most academic environments. This is a barrier into collecting the large and consistent datasets required for machine learning analyses of microscopy data. We demonstrate hardware modifications and software to bring the features of modern computerized microscopes to decades-old legacy laboratory inverted microscopes. We demonstrate automation of X-Y positioning, focus stacking, image acquisition and image storage.
Abstract: A search is presented for a heavy scalar (H) or pseudo-scalar (A) predicted by the two-Higgs-doublet models, where the H/A is produced in association with a top-quark pair $$(t\bar{t}H/A),$$ ( t t ¯ H / A ) , and with the H/A decaying into a $$t\bar{t}$$ t t ¯ pair. The full LHC Run 2 proton–proton collision data collected by the ATLAS experiment is used, corresponding to an integrated luminosity of $$139~\text {fb}^{-1}.$$ 139 fb - 1 . Events are selected requiring exactly one or two opposite-charge electrons or muons. Data-driven corrections are applied to improve the modelling of the $$t\bar{t}$$ t t ¯ +jets background in the regime with high jet and b-jet multiplicities. These include a novel multi-dimensional kinematic reweighting based on a neural network trained using data and simulations. An H/A-mass parameterised graph neural network is trained to optimise the signal-to-background discrimination. In combination with the previous search performed by the ATLAS Collaboration in the multilepton final state, the observed upper limits on the $$t\bar{t}H/A \rightarrow t\bar{t}t\bar{t}$$ t t ¯ H / A → t t ¯ t t ¯ production cross-section at 95% confidence level range between 14 fb and 5.0 fb for an H/A with mass between 400 $$\text {GeV}$$ GeV and 1000 $$\text {GeV}$$ GeV , respectively. Assuming that both the H and A contribute to the $$t\bar{t}t\bar{t}$$ t t ¯ t t ¯ cross-section, $$\tan \beta $$ tan β values below 1.7 or 0.7 are excluded for a mass of 400 $$\text {GeV}$$ GeV or 1000 $$\text {GeV}$$ GeV , respectively. The results are also used to constrain a model predicting the pair production of a colour-octet scalar, with the scalar decaying into a $$t\bar{t}$$ t t ¯ pair.
Abstract: This paper describes an algorithm for reconstructing and identifying a highly collimated hadronically decaying $$\tau $$ τ -lepton pair with low transverse momentum. When two $$\tau $$ τ -leptons are highly collimated, their visible decay products might overlap, degrading the reconstruction performance for each of the $$\tau $$ τ -leptons. A dedicated treatment attempting to tag the $$\tau $$ τ -lepton pair as a single object is required. The reconstruction algorithm is based on a large radius jet and its associated two leading subjets, and the identification uses a boosted decision tree to discriminate between signatures from $$\tau ^+\tau ^-$$ τ + τ - systems and those arising from QCD jets. The efficiency of the identification algorithm is measured in $$Z\gamma $$ Z γ events using proton–proton collision data at $$\sqrt{s}=13$$ s = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider between 2015 and 2018, corresponding to an integrated luminosity of $$139\,\text{ fb}^{-1}$$ 139 fb - 1 . The resulting data-to-simulation scale factors are close to unity with uncertainties ranging from 26 to 37%.
Abstract : A search for pair production of vector-like leptons coupling to first- and second-generation Standard Model leptons is presented. The search is based on a dataset of proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb −1. Events are categorised depending on the flavour and multiplicity of leptons (electrons or muons), as well as on the scores of a deep neural network targeting particular signal topologies according to the decay modes of the vector-like leptons. In each of the signal regions, the scalar sum of the transverse momentum of the leptons and the missing transverse momentum is analysed. The main background processes are estimated using dedicated control regions in a simultaneous fit with the signal regions to data. No significant excess above the Standard Model background expectation is observed and limits are set at 95% confidence level on the production cross-sections of vector-like electrons and muons as a function of the vector-like lepton mass, separately for SU(2) doublet and singlet scenarios. The resulting mass lower limits are 1220 GeV (1270 GeV) and 320 GeV (400 GeV) for vector-like electrons (muons) in the doublet and singlet scenarios, respectively.
Abstract : A measurement of the ratio of the branching fractions, R τ/e = B(W → τν)/B(W → eν), is performed using a sample of W bosons originating from top-quark decays to final states containing τ-leptons or electrons. This measurement uses pp collisions at $$ \sqrt{s} $$ s = 13 TeV, collected by the ATLAS experiment at the Large Hadron Collider during Run 2, corresponding to an integrated luminosity of 140 fb −1. The W → τν τ (with τ → eν e ν τ ) and W → eν e decays are distinguished using the differences in the impact parameter distributions and transverse momentum spectra of the electrons. The measured ratio of branching fractions R τ/e = 0.975 ± 0.012 (stat.) ± 0.020 (syst.), is consistent with the Standard Model assumption of lepton flavour universality in W-boson decays.
