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

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector

A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV

Search for direct stau production in events with two hadronic tau-leptons in root s=13 TeV pp collisions with the ATLAS detector

A search for the direct production of the supersymmetric partners ofτ-leptons (staus) in final stateswith two hadronically decayingτ-leptons is presented. The analysis uses a dataset of pp collisions corresponding to an integrated luminosity of139fb−1, recorded with the ATLAS detector at the LargeHadron Collider at a center-of-mass energy of 13 TeV. No significant deviation from the expected StandardModel background is observed. Limits are derived in scenarios of direct production of stau pairs with eachstau decaying into the stable lightest neutralino and oneτ-lepton in simplified models where the two staumass eigenstates are degenerate. Stau masses from 120 GeV to 390 GeV are excluded at 95% confidencelevel for a massless lightest neutralino

Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente

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

Construction techniques and performances of a full size prototype Micromegas chamber for the ATLAS muon spectrometer upgrade

A full scale 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 used in constructing the single modules of the chamber in various INFN laboratories and the final assembly at the Frascati National Laboratories (LNF). Results of the chamber exposure to the CERN H8 beam line in June 2016 are also presented. The performances achieved in the construction and the results of the test beam are compared with the requirements, which are imposed by the severe environment during the data-taking of the LHC foreseen for the next years

Measurements of long-range azimuthal anisotropies and associated Fourier coefficients for pp collisions at √s=5.02 and 13 TeV and p+Pb collisions at √sNN=5.02 TeV with the ATLAS detector

ATLAS measurements of two-particle correlations are presented for √s=5.02 and 13 TeV ppcollisions and for √sNN=5.02 TeV p+Pb collisions at the LHC. The correlation functions are measured as a function of relative azimuthal angle Δϕ, and pseudorapidity separation Δη, using charged particles detected within the pseudorapidity interval |η|2, is studied using a template fitting procedure to remove a “back-to-back” contribution to the correlation function that primarily arises from hard-scattering processes. In addition to the elliptic, cos (2Δϕ), modulation observed in a previous measurement, the pp correlation functions exhibit significant cos (3Δϕ) and cos (4Δϕ) modulation. The Fourier coefficients vn, n associated with the cos (nΔϕ) modulation of the correlation functions for n=2–4 are measured as a function of charged-particle multiplicity and charged-particle transverse momentum. The Fourier coefficients are observed to be compatible with cos (nϕ) modulation of per-event single-particle azimuthal angle distributions. The single-particle Fourier coefficients vn are measured as a function of charged-particle multiplicity, and charged-particle transverse momentum for n=2–4. The integrated luminosities used in this analysis are, 64nb−1 for the √s=13 TeV pp data, 170 nb−1 for the √ s = 5.02 TeV pp data, and 28 nb−1 for the √sNN = 5.02 TeV p+Pb data

Searches for exclusive Higgs and Z boson decays into J/ψγ,ψ(2S)γ,and Υ(nS)γ at √s=13 TeV with the ATLAS detector

Searches for the exclusive decays of the Higgs and Z bosons into a J/ψ,ψ(2S), or Υ(nS)(n=1,2,3) meson and a photon are performed with a pp collision data sample corresponding to an integrated luminosity of 36.1 fb −1 collected at √s =13 TeV with the ATLAS detector at the CERN Large Hadron Collider. No significant excess of events is observed above the expected backgrounds, and 95% confidence-level upper limits on the branching fractions of the Higgs boson decays to J/ψγ, ψ(2S)γ,and Υ(nS)γ of 3.5×10 −4, 2.0×10−3,and(4.9,5.9,5.7)×10 −4,respectively, are obtained assuming Standard Model production. The corresponding 95% confidence-level upper limits for the branching fractions of the Z boson decays are 2.3×10 −6, 4.5×10 −6 and (2.8,1.7,4.8)×10 −6, respectively