Large-size Resistive Micromegas have been chosen for the upgrade of the forward muon spectrometer of the ATLAS experiment, the New Small Wheel project. These chambers, together with small-strip Thin Gap Chambers (sTGC), allow reconstruction of high-momentum muon tracks in a high-radiation environment and provide a robust low-threshold single-muon trigger. A collaboration of seven INFN units built 32 SM1 type chambers, corresponding to one fourth of the total number needed for this upgrade. Each SM1 chamber has a surface of approximately 2 m2 and four sensitive layers. The production was shared among five INFN construction sites and it was completed in fall 2020. The construction methods, as well as the results of the quality tests done on components of the detector and on the assembled chambers, are reported in the present paper.

This Letter reports the observation of WWW production and a measurement of its cross section using 139 fb^{-1} of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. Events with two same-sign leptons (electrons or muons) and at least two jets, as well as events with three charged leptons, are selected. A multivariate technique is then used to discriminate between signal and background events. Events from WWW production are observed with a significance of 8.0 standard deviations, where the expectation is 5.4 standard deviations. The inclusive WWW production cross section is measured to be 820±100 (stat)±80 (syst) fb, approximately 2.6 standard deviations from the predicted cross section of 511±18 fb calculated at next-to-leading-order QCD and leading-order electroweak accuracy.

The first measurement of longitudinal decorrelations of harmonic flow amplitudes v_{n} for n=2-4 in Xe+Xe collisions at sqrt[s_{NN}]=5.44  TeV is obtained using 3  μb^{-1} of data with the ATLAS detector at the LHC. The decorrelation signal for v_{3} and v_{4} is found to be nearly independent of collision centrality and transverse momentum (p_{T}) requirements on final-state particles, but for v_{2} a strong centrality and p_{T} dependence is seen. When compared with the results from Pb+Pb collisions at sqrt[s_{NN}]=5.02  TeV, the longitudinal decorrelation signal in midcentral Xe+Xe collisions is found to be larger for v_{2}, but smaller for v_{3}. Current hydrodynamic models reproduce the ratios of the v_{n} measured in Xe+Xe collisions to those in Pb+Pb collisions but fail to describe the magnitudes and trends of the ratios of longitudinal flow decorrelations between Xe+Xe and Pb+Pb. The results on the system-size dependence provide new insights and an important lever arm to separate effects of the longitudinal structure of the initial state from other early and late time effects in heavy-ion collisions.

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A full-size prototype of a Micromegas precision tracking chamber for the upgrade of the ATLAS detector at the LHC Collider has been built between October 2015 and April 2016. This paper describes in detail the procedures followed in the construction of the components of the chamber in various INFN laboratories and the final assembly in the Laboratori Nazionali di Frascati (LNF). In addition, the results of the chamber exposure to a particle beam at SPS/H8 at CERN in June 2016 are presented. The performances obtained in the construction and the results of the test beam are compared with the requirements set in order to sustain the high radiation levels expected during the data-taking of the LHC in the next years.

The dynamics of isolated-photon plus jet production in $pp$ collisions at $\sqrt{s}$ = 13 TeV were studied with the ATLAS detector at the LHC, using a dataset with an integrated luminosity of 3.2 fb$^{-1}$. The photons were reconstructed for photon transverse energies larger than 125 GeV. The jets were identified using the anti-$k_{t}$ algorithm with radius parameter R=0.4 and selected in the rapidity range $|y| $ 100 GeV. Measurements of isolated-photon plus jet cross sections are presented as functions of the photon transverse energy, the jet transverse momentum, the azimuthal separation between the selected photon and the jet, the photon-jet invariant mass and the scattering angle in the photon-jet centre-of-mass system. The leading-logarithm parton-shower preditions from SHERPA and PYTHIA as well as the next-to-leading order QCD calculations from JETPHOX and multi-leg plus parton shower NLO SHERPA are compared to the measurements.

BACKGROUND:Angiotensin-converting enzyme inhibitors reduce mortality and remodeling after myocardial infarction in patients with left ventricular dysfunction.METHODS:Perindopril and Remodeling in Elderly With Acute Myocardial Infarction (PREAMI), a double-blind, randomized, parallel-group, multicenter, placebo-controlled study, determined whether similar benefits occur in elderly postinfarction patients with preserved left ventricular function. A total of 1252 patients 65 years or older with a left ventricular ejection fraction of 40% or higher and recent acute myocardial infarction were randomized to receive perindopril erbumine or placebo (8 mg/d) for 12 months. The combined primary end point was death, hospitalization for heart failure, or left ventricular remodeling. Secondary end points included cardiovascular death, hospitalization for reinfarction or angina, and revascularization.RESULTS:The primary end point occurred in 181 patients (35%) taking perindopril and 290 patients (57%) taking placebo, with a significant absolute risk reduction of 0.22 (95% confidence interval, 0.16 to 0.28; P<.001). A total of 126 patients (28%) and 226 patients (51%) in the perindopril and placebo groups, respectively, experienced remodeling. The mean increase in left ventricle end-diastolic volume was 0.7 mL with perindopril compared with 4.0 mL with placebo (P<.001). In the perindopril group, 40 deaths (6%) and 22 hospitalizations (4%) for heart failure occurred, whereas 37 deaths (6%) and 30 hospitalizations (5%) occurred in the placebo group. Treatment did not affect death, whereas the hospitalization rate for heart failure was slightly reduced (absolute risk reduction, 0.01; 95% confidence interval, -0.01 to 0.02). No treatment effect on other secondary end points was detected.CONCLUSION:We found that 1-year treatment with 8 mg/d of perindopril reduces progressive left ventricular remodeling that can occur even in the presence of small infarct size, but it was not associated with better clinical outcomes.

Background-Unstable angina and non-Q-wave myocardial infarction involve coronary arterial plaque rupture, platelet activation, and thrombus formation. This study tested the benefit of different doses of lamifiban (a platelet IIb/IIIa antagonist) alone and in combination with heparin in patients with these conditions to select the most promising lamifiban regimen for subsequent evaluation.Methods and Results-At 273 hospitals in 20 countries, 2282 patients were randomly assigned to lamifiban (2x2 factorial design: low-dose [1 mu g/min] with and without heparin versus high-dose [5 mu g/min] with and without heparin) or to standard therapy (placebo and heparin). All patients received aspirin. The composite primary end point of death or nonfatal myocardial infarction at 30 days occurred in 11.7% of those receiving standard therapy, 10.6% receiving low-dose lamifiban, and 12.0% receiving high-dose lamifiban (P=0.668). By 6 months, this composite was lowest for those assigned to low-dose lamifiban (P=0.027) and intermediate for those assigned to high-dose lamifiban (P=0.450) compared with control (13.7%, 16.4%, and 17.9%, respectively). Compared with control, the combination of high-dose lamifiban and heparin resulted in more intermediate or major bleeding (12.1% versus 5.5%; P=0.002) and a similar rate of ischemic events. Conversely, low-dose lamifiban and heparin yielded similar bleeding rates as in the control group but fewer ischemic events at 6 months (12.6% versus 17.9%; P=0.025).Conclusions-In unstable angina and non-Q-wave infarction, platelet IIb/IIIa antagonism with lamifiban reduces adverse ischemic events at 6 months beyond that of aspirin and heparin therapy. The role of conjunctive heparin remains uncertain but appears more favorable with low-dose IIb/IIIa antagonism. Larger-scale study is needed to more reliably estimate these effects.