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

Search for pairs of scalar leptoquarks decaying into quarks and electrons or muons in √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

Search for new non-resonant phenomena in high-mass dilepton final states with the ATLAS detector

A search for new physics with non-resonant signals in dielectron and dimuon final states in the mass range above 2 TeV is presented. This is the first search for non-resonant signals in dilepton final states at the LHC to use a background estimate from the data. The data, corresponding to an integrated luminosity of 139 fb−1, were recorded by the ATLAS experiment in proton-proton collisions at a center-of-mass energy of s = 13 TeV during Run 2 of the Large Hadron Collider. The benchmark signal signature is a two-quark and two-lepton contact interaction, which would enhance the dilepton event rate at the TeV mass scale. To model the contribution from background processes a functional form is fit to the dilepton invariant-mass spectra in data in a mass region below the region of interest. It is then extrapolated to a high-mass signal region to obtain the expected background there. No significant deviation from the expected background is observed in the data. Upper limits at 95% CL on the number of events and the visible cross-section times branching fraction for processes involving new physics are provided. Observed (expected) 95% CL lower limits on the contact interaction energy scale reach 35.8 (37.6) TeV. [Figure not available: see fulltext.

Search for a scalar partner of the top quark in the all-hadronic t\bar{t} plus missing transverse momentum final state at \sqrt{s} =13 TeV with the ATLAS detector

A search for direct pair production of scalar partners of the top quark (top squarks or scalar third-generation up-type leptoquarks) in the all-hadronic t\bar{t} plus missing transverse momentum final state is presented. The analysis of 139 fb^{-1} \sqrt{s} = 13 TeV proton–proton collision data collected using the ATLAS detector at the LHC yields no significant excess over the Standard Model background expectation. To interpret the results, a supersymmetric model is used where the top squark decays via \tilde{t} \rightarrow t^{(*)} \tilde{x}\frac{0}{1}, with t^{(*)} denoting an on-shell (off-shell) top quark and \tilde{x}\frac{0}{1} the lightest neutralino. Three specific event selections are optimised for the following scenarios. In the scenario where m_{tilde{t}} > m_{t} + m_{\tilde{x}\frac{0}{1}}, top squark masses are excluded in the range 400–1250 GeV for \tilde{x}\frac{0}{1} masses below 200 GeV at 95% confidence level. In the situation where m_{tilde{t}} \sim m_{t} + M_{\tilde{x}\frac{0}{1}}, top squark masses in the range 300–630 GeV are excluded, while in the case where m_{tilde{t}} < m_{W} + m_{b} + m_{\tilde{x}\frac{0}{1}} (with m_{tilde{t}}) \geq 5 GeV), considered for the first time in an ATLAS all-hadronic search, top squark masses in the range 300–660 GeV are excluded. Limits are also set for scalar third-generation up-type leptoquarks, excluding leptoquarks with masses below 1240 GeV when considering only leptoquark decays into a top quark and a neutrino

Measurement of the charge asymmetry in top-quark pair production in association with a photon with the ATLAS experiment

A measurement of the charge asymmetry in top-quark pair (tt ̄) production in association with a photon is presented. The measurement is performed in the single-lepton tt ̄ decay channel using proton–proton collision data collected with the ATLAS detector at the Large Hadron Collider at CERN at a centre-of-mass-energy of 13 TeV during the years 2015–2018, corresponding to an integrated luminosity of 139 fb−1. The charge asymmetry is obtained from the distribution of the difference of the absolute rapidities of the top quark and antiquark using a profile likelihood unfolding approach. It is measured to be AC=−0.003±0.029 in agreement with the Standard Model expectation

Measurements of inclusive and differential cross-sections of combined t t ¯ γ and tWγ production in the eμ channel at 13 TeV with the ATLAS detector

Abstract: Inclusive and differential cross-sections for the production of top quarks in association with a photon are measured with proton-proton collision data corresponding to an integrated luminosity of 139 fb−1. The data were collected by the ATLAS detector at the LHC during Run 2 between 2015 and 2018 at a centre-of-mass energy of 13 TeV. The measurements are performed in a fiducial volume defined at parton level. Events with exactly one photon, one electron and one muon of opposite sign, and at least two jets, of which at least one is b-tagged, are selected. The fiducial cross-section is measured to be 39.6−2.3+2.7 fb. Differential cross-sections as functions of several observables are compared with state-of-the-art Monte Carlo simulations and next-to-leading-order theoretical calculations. These include cross-sections as functions of photon kinematic variables, angular variables related to the photon and the leptons, and angular separations between the two leptons in the event. All measurements are in agreement with the predictions from the Standard Model

Measurements of inclusive and differential cross-sections of combined t t ¯ γ and tWγ production in the eμ channel at 13 TeV with the ATLAS detector

Abstract: Inclusive and differential cross-sections for the production of top quarks in association with a photon are measured with proton-proton collision data corresponding to an integrated luminosity of 139 fb−1. The data were collected by the ATLAS detector at the LHC during Run 2 between 2015 and 2018 at a centre-of-mass energy of 13 TeV. The measurements are performed in a fiducial volume defined at parton level. Events with exactly one photon, one electron and one muon of opposite sign, and at least two jets, of which at least one is b-tagged, are selected. The fiducial cross-section is measured to be 39.6−2.3+2.7 fb. Differential cross-sections as functions of several observables are compared with state-of-the-art Monte Carlo simulations and next-to-leading-order theoretical calculations. These include cross-sections as functions of photon kinematic variables, angular variables related to the photon and the leptons, and angular separations between the two leptons in the event. All measurements are in agreement with the predictions from the Standard Model