ATLAS data quality operations and performance for 2015-2018 data-taking

The ATLAS detector at the Large Hadron Collider reads out particle collision data from over 100 million electronic channels at a rate of approximately 100 kHz, with a recording rate for physics events of approximately 1 kHz. Before being certified for physics analysis at computer centres worldwide, the data must be scrutinised to ensure they are clean from any hardware or software related issues that may compromise their integrity. Prompt identification of these issues permits fast action to investigate, correct and potentially prevent future such problems that could render the data unusable. This is achieved through the monitoring of detector-level quantities and reconstructed collision event characteristics at key stages of the data processing chain. This paper presents the monitoring and assessment procedures in place at ATLAS during 2015–2018 data-taking. Through the continuous improvement of operational procedures, ATLAS achieved a high data quality efficiency, with 95.6% of the recorded proton-proton collision data collected at √s=13 TeV certified for physics analysis.Fil: Orellana, Gonzalo Enrique. Universidad Nacional de La Plata. Facultad de Ciencias Exactas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Alconada Verzini, María Josefina. Tel Aviv University; Israel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Arduh, Francisco Anuar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Dova, Maria Teresa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Monticelli, Fernando Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Hoya, Joaquín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Wahlberg, Hernan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Abed Abud, A.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Ahmad, A.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Alderweireldt, S.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Aleksa, M.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Allaire, C.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Aranzabal Barrio, N.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Bielski, R.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Bortfeldt, J.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Boyd, J.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Butti, P.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Buttinger, W.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Camincher, C.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Campana, S.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Ellis, N.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Elsing, M.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Farthouat, P.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Fassnacht, P.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Heinrich, L.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Iengo, P.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Morley, A. K.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Mornacchi, G. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Moschovakos, P.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Meehan, S.. Cern - European Organization For Nuclear Research. The Cern Council; Suiz

Search for pairs of scalar leptoquarks decaying into quarks and electrons or muons in s√s = 13 TeV pp collisions with the ATLAS detector

A search for new-physics resonances decaying into a lepton and a jet performed by the ATLAS experiment is presented. Scalar leptoquarks pair-produced in pp collisions at s√ = 13 TeV at the Large Hadron Collider are considered using an integrated luminosity of 139 fb−1, corresponding to the full Run 2 dataset. They are searched for in events with two electrons or two muons and two or more jets, including jets identified as arising from the fragmentation of c- or b-quarks. The observed yield in each channel is consistent with the Standard Model background expectation. Leptoquarks with masses below 1.8 TeV and 1.7 TeV are excluded in the electron and muon channels, respectively, assuming a branching ratio into a charged lepton and a quark of 100%, with minimal dependence on the quark flavour. Upper limits on the aforementioned branching ratio are also given as a function of the leptoquark mass.Fil: Alonso, Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Alconada Verzini, María Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universitat Tel Aviv; IsraelFil: Arduh, Francisco Anuar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Dova, Maria Teresa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Hoya, Joaquín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Monticelli, Fernando Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Orellana, Gonzalo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Wahlberg, Hernan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Abed Abud, A.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Ahmad, A.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Alderweireldt, S.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Aleksa, M.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Allaire, C.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Aranzabal Barrio, N.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Bielski, R.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Bortfeldt, J.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Boyd, J.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Butti, P.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Buttinger, W.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Camincher, C.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Campana, S.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Ellis, N.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Elsing, M.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Farthouat, P.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Fassnacht, P.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Heinrich, L.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Iengo, P.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Morley, A. K.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Mornacchi, G.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Moschovakos, P.. Cern - European Organization For Nuclear Research. The Cern Council; Suiz

Performance of electron and photon triggers in ATLAS during LHC Run 2.

Electron and photon triggers covering transverse energies from 5 GeV to several TeV are essential for the ATLAS experiment to record signals for a wide variety of physics: from Standard Model processes to searches for new phenomena in both proton–proton and heavy-ion collisions. To cope with a fourfold increase of peak LHC luminosity from 2015 to 2018 (Run 2), to 2.1×1034 cm−2 s −1 , and a similar increase in the number of interactions per beam-crossing to about 60, trigger algorithms and selections were optimised to control the rates while retaining a high efficiency for physics analyses. For proton–proton collisions, the single-electron trigger efficiency relative to a single-electron offline selection is at least 75% for an offline electron of 31 GeV, and rises to 96% at 60 GeV; the trigger efficiency of a 25 GeV leg of the primary diphoton trigger relative to a tight offline photon selection is more than 96% for an offline photon of 30 GeV. For heavy-ion collisions, the primary electron and photon trigger efficiencies relative to the corresponding standard offline selections are at least 84% and 95%, respectively, at 5 GeV above the corresponding trigger threshold.Fil: Wahlberg, Hernan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Alconada Verzini, María Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universitat Tel Aviv; IsraelFil: Alonso, Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Arduh, Francisco Anuar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Dova, Maria Teresa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Hoya, Joaquín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Monticelli, Fernando Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Orellana, Gonzalo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Abed Abud, A.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Ahmad,A.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Alderweireldt, S.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Aleksa, M.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Allaire, C.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Aranzabal Barrio, N.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Bielski, R.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Bortfeldt, J.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Boyd, J.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Butti, P.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Buttinger, W.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Camincher, C.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Campana, S.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Ellis, N.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Elsing, M.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Morley, A. K.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Mornacchi, G.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Moschovakos, P.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Meehan, S.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Meng, L.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Stewart, G. A.. Cern - European Organization For Nuclear Research. The Cern Council; SuizaFil: Stockton, M. C.. Cern - European Organization For Nuclear Research. The Cern Council; Suiz

Differential cross-section measurements for the electroweak production of dijets in association with a Z boson in proton–proton collisions at ATLAS

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UA

Evidence for tt¯ tt¯ production in the multilepton final state in proton–proton collisions at √s=13 TeV with the ATLAS detector

A search is presented for four-top-quark production using an integrated luminosity of 139 fb- 1 of proton–proton collision data at a centre-of-mass energy of 13TeV collected by the ATLAS detector at the LHC. Events are selected if they contain a same-sign lepton pair or at least three leptons (electrons or muons). Jet multiplicity, jet flavour and event kinematics are used to separate signal from the background through a multivariate discriminant, and dedicated control regions are used to constrain the dominant backgrounds. The four-top-quark production cross section is measured to be 24-6+7 fb. This corresponds to an observed (expected) significance with respect to the background-only hypothesis of 4.3 (2.4) standard deviations and provides evidence for this process

Production of ϒ(nS) mesons in Pb + Pb and pp collisions at 5.02 TeV

A measurement of the production of vector bottomonium states, ϒ(1S), ϒ(2S), and ϒ(3S), in Pb + Pb and pp collisions at a center-of-mass energy per nucleon pair of 5.02 TeV is presented. The data correspond to integrated luminosities of 1.38 nb-1 of Pb + Pb data collected in 2018, 0.44 nb-1 of Pb + Pb data collected in 2015, and 0.26 fb-1 of pp data collected in 2017 by the ATLAS detector at the Large Hadron Collider. The measurements are performed in the dimuon decay channel for transverse momentum pμμT < 30 GeV, absolute rapidity |yμμ| < 1.5, and Pb + Pb event centrality 0-80%. The production rates of the three bottomonium states in Pb + Pb collisions are compared with those in pp collisions to extract the nuclear modification factors as functions of event centrality, pμμT, and |yμμ|. In addition, the suppression of the excited states relative to the ground state is studied. The results are compared with theoretical model calculations

Differential tt¯cross-section measurements using boosted top quarks in the all-hadronic final state with 139 fb−1 of ATLAS data

Measurements of single-, double-, and triple-differential cross-sections are presented for boosted top-quark pair-production in 13 TeV proton–proton collisions recorded by the ATLAS detector at the LHC. The top quarks are observed through their hadronic decay and reconstructed as large-radius jets with the leading jet having transverse momentum (pT) greater than 500 GeV. The observed data are unfolded to remove detector effects. The particle-level cross-section, multiplied by the tt¯ → WWbb¯ branching fraction and measured in a fiducial phase space defined by requiring the leading and second-leading jets to have pT> 500 GeV and pT> 350 GeV, respectively, is 331 ± 3(stat.) ± 39(syst.) fb. This is approximately 20% lower than the prediction of 398−49+48 fb by Powheg+Pythia 8 with next-to-leading-order (NLO) accuracy but consistent within the theoretical uncertainties. Results are also presented at the parton level, where the effects of top-quark decay, parton showering, and hadronization are removed such that they can be compared with fixed-order next-to-next-to-leading-order (NNLO) calculations. The parton-level cross-section, measured in a fiducial phase space similar to that at particle level, is 1.94 ± 0.02(stat.) ± 0.25(syst.) pb. This agrees with the NNLO prediction of 1.96−0.17+0.02 pb. Reasonable agreement with the differential cross-sections is found for most NLO models, while the NNLO calculations are generally in better agreement with the data. The differential cross-sections are interpreted using a Standard Model effective field-theory formalism and limits are set on Wilson coefficients of several four-fermion operators. [Figure not available: see fulltext.]

Search for heavy resonances decaying into a pair of Z bosons in the ℓ⁺ ℓ ¯ℓ'⁺ ℓ'¯ and ℓ⁺ ℓ¯ν\bar{ν} states using 139 fb¯¹ of proton–proton collisions at \sqrt{s} = 13 TeV with the ATLAS detector

A search for heavy resonances decaying into a pair of Z bosons leading to \ell ^+\ell ^-\ell '^+\ell '^- and \ell ^+\ell ^-\nu {{\bar{\nu }}} final states, where \ell stands for either an electron or a muon, is presented. The search uses proton–proton collision data at a centre-of-mass energy of 13 TeV collected from 2015 to 2018 that corresponds to the integrated luminosity of 139 \mathrm {fb}^{-1} recorded by the ATLAS detector during Run 2 of the Large Hadron Collider. Different mass ranges spanning 200 GeV to 2000 GeV for the hypothetical resonances are considered, depending on the final state and model. In the absence of a significant observed excess, the results are interpreted as upper limits on the production cross section of a spin-0 or spin-2 resonance. The upper limits for the spin-0 resonance are translated to exclusion contours in the context of Type-I and Type-II two-Higgs-doublet models, and the limits for the spin-2 resonance are used to constrain the Randall–Sundrum model with an extra dimension giving rise to spin-2 graviton excitations

Cross-section measurements for the production of a Z boson in association with high-transverse-momentum jets in pp collisions at √s = 13 TeV with the ATLAS detector

Cross-section measurements for a Z boson produced in association with high-transverse-momentum jets (p T ≥ 100 GeV) and decaying into a charged-lepton pair (e + e − , μ + μ −) are presented. The measurements are performed using proton–proton collisions at s = 13 TeV corresponding to an integrated luminosity of 139 fb −1 collected by the ATLAS experiment at the LHC. Measurements of angular correlations between the Z boson and the closest jet are performed in events with at least one jet with p T ≥ 500 GeV. Event topologies of particular interest are the collinear emission of a Z boson in dijet events and a boosted Z boson recoiling against a jet. Fiducial cross sections are compared with state-of-the-art theoretical predictions. The data are found to agree with next-to-next-to-leading-order predictions by NNLOjet and with the next-to-leading-order multi-leg generators MadGraph5_aMC@NLO and Sherpa. [Figure not available: see fulltext.]

Optimisation of large-radius jet reconstruction for the ATLAS detector in 13 TeV proton–proton collisions

Jet substructure has provided new opportunities for searches and measurements at the LHC, and has seen continuous development since the optimization of the large-radius jet definition used by ATLAS was performed during Run 1. A range of new inputs to jet reconstruction, pile-up mitigation techniques and jet grooming algorithms motivate an optimisation of large-radius jet reconstruction for ATLAS. In this paper, this optimisation procedure is presented, and the performance of a wide range of large-radius jet definitions is compared. The relative performance of these jet definitions is assessed using metrics such as their pileup stability, ability to identify hadronically decaying W bosons and top quarks with large transverse momenta. A new type of jet input object, called a ‘unified flow object’ is introduced which combines calorimeter- and inner-detector-based signals in order to achieve optimal performance across a wide kinematic range. Large-radius jet definitions are identified which significantly improve on the current ATLAS baseline definition, and their modelling is studied using pp collisions recorded by the ATLAS detector at \sqrt{s}=13~\text {TeV} during 2017