2021, Aad, G., Abbott, B., Abbott, D. C., Abed, Abud, A., Belotskiy, K., Belyaev, N. L., Bulekov, O., Kurova, A., Ponomarenko, D., Proklova, N., Pyatiizbyantseva, D., Romaniouk, A., Smirnov, N., Smirnov, S. Y., Smirnov, Y., Soldatov, E. Y., Tikhomirov, V. O., Timoshenko, S., Vorobev, K., Белоцкий, Константин Михайлович, Булеков, Олег Владимирович, Курова, Анастасия Сергеевна, Пятиизбянцева, Диана Николаевна, Романюк, Анатолий Самсонович, Смирнов, Сергей Юрьевич, Смирнов, Юрий Сергеевич, Солдатов, Евгений Юрьевич, Тихомиров, Владимир Олегович, Тимошенко, Сергей Леонидович, Воробьёв, Константин Александрович

© 2021, The Author(s).A search for new phenomena with top quark pairs in final states with one isolated electron or muon, multiple jets, and large missing transverse momentum is performed. Signal regions are designed to search for two-, three-, and four-body decays of the directly pair-produced supersymmetric partner of the top quark (stop). Additional signal regions are designed specifically to search for spin-0 mediators that are produced in association with a pair of top quarks and decay into a pair of dark-matter particles. The search is performed using the Large Hadron Collider proton-proton collision dataset at a centre-of-mass energy of s = 13 TeV recorded by the ATLAS detector from 2015 to 2018, corresponding to an integrated luminosity of 139 fb−1. No significant excess above the Standard Model background is observed, and limits at 95% confidence level are set in the stop-neutralino mass plane and as a function of the mediator mass or the dark-matter particle mass. Stops are excluded up to 1200 GeV (710 GeV) in the two-body (three-body) decay scenario. In the four-body scenario stops up to 640 GeV are excluded for a stop-neutralino mass difference of 60 GeV. Scalar and pseudoscalar dark-matter mediators are excluded up to 200 GeV when the coupling strengths of the mediator to Standard Model and dark-matter particles are both equal to one and when the mass of the dark-matter particle is 1 GeV. [Figure not available: see fulltext.]

2020, Aaboud, M., Aad, G., Abbott, B., Abbott, D. C., Belotskiy, K., Belyaev, N. L., Bulekov, O., Kantserov, V. A., Kurova, A., Ponomarenko, D., Proklova, N., Romaniouk, A., Shulga, E., Smirnov, N., Smirnov, S. Y., Smirnov, Y., Soldatov, E. Y., Tikhomirov, V. O., Timoshenko, S., Vorobev, K., Белоцкий, Константин Михайлович, Булеков, Олег Владимирович, Курова, Анастасия Сергеевна, Романюк, Анатолий Самсонович, Смирнов, Сергей Юрьевич, Смирнов, Юрий Сергеевич, Солдатов, Евгений Юрьевич, Тихомиров, Владимир Олегович, Тимошенко, Сергей Леонидович, Воробьёв, Константин Александрович

© 2020, The Author(s).A measurement of the production of a prompt J/ψ meson in association with a W± boson with W± → μν and J/ψ → μ+μ− is presented for J/ψ transverse momenta in the range 8.5–150 GeV and rapidity |yJ/ψ| < 2.1 using ATLAS data recorded in 2012 at the LHC. The data were taken at a proton-proton centre-of-mass energy of s = 8 TeV and correspond to an integrated luminosity of 20.3 fb−1. The ratio of the prompt J/ψ plus W± cross-section to the inclusive W± cross-section is presented as a differential measurement as a function of J/ψ transverse momenta and compared with theoretical predictions using different double-parton-scattering cross-sections. [Figure not available: see fulltext.].

2022, Belotskiy, K., Belyaev, N. L., Bulekov, O., Kurova, A., Ponomarenko, D., Proklova, N., Pyatiizbyantseva, D., Romaniouk, A., Smirnov, S. Y., Smirnov, Y., Soldatov, E. Y., Tikhomirov, V. O., Timoshenko, S., Vorobev, K., Белоцкий, Константин Михайлович, Булеков, Олег Владимирович, Курова, Анастасия Сергеевна, Пятиизбянцева, Диана Николаевна, Романюк, Анатолий Самсонович, Смирнов, Сергей Юрьевич, Смирнов, Юрий Сергеевич, Солдатов, Евгений Юрьевич, Тихомиров, Владимир Олегович, Тимошенко, Сергей Леонидович, Воробьёв, Константин Александрович

This paper presents an analysis at next-to-next-to-leading order in the theory of quantum chromodynamics for the determination of a new set of proton parton distribution functions using diverse measurements in pp collisions at s=7, 8 and 13 TeV, performed by the ATLAS experiment at the Large Hadron Collider, together with deep inelastic scattering data from ep collisions at the HERA collider. The ATLAS data sets considered are differential cross-section measurements of inclusive W± and Z/ γ∗ boson production, W± and Z boson production in association with jets, tt¯ production, inclusive jet production and direct photon production. In the analysis, particular attention is paid to the correlation of systematic uncertainties within and between the various ATLAS data sets and to the impact of model, theoretical and parameterisation uncertainties. The resulting set of parton distribution functions is called ATLASpdf21. © 2022, The Author(s).

2020, Aad, G., Abbott, B., Abbott, D. C., Abed, Abud, A., Belotskiy, K., Belyaev, N. L., Bulekov, O., Kantserov, V. A., Kurova, A., Ponomarenko, D., Proklova, N., Romaniouk, A., Smirnov, N., Smirnov, S. Y., Smirnov, Y., Soldatov, E. Y., Tikhomirov, V. O., Timoshenko, S., Vorobev, K., Белоцкий, Константин Михайлович, Булеков, Олег Владимирович, Курова, Анастасия Сергеевна, Романюк, Анатолий Самсонович, Смирнов, Сергей Юрьевич, Смирнов, Юрий Сергеевич, Солдатов, Евгений Юрьевич, Тихомиров, Владимир Олегович, Тимошенко, Сергей Леонидович, Воробьёв, Константин Александрович

© 2020, The Author(s).A search for new resonances decaying into a pair of jets is reported using the dataset of proton-proton collisions recorded at s = 13 TeV with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to an integrated luminosity of 139 fb−1. The distribution of the invariant mass of the two leading jets is examined for local excesses above a data-derived estimate of the Standard Model background. In addition to an inclusive dijet search, events with jets identified as containing b-hadrons are examined specifically. No significant excess of events above the smoothly falling background spectra is observed. The results are used to set cross-section upper limits at 95% confidence level on a range of new physics scenarios. Model-independent limits on Gaussian-shaped signals are also reported. The analysis looking at jets containing b-hadrons benefits from improvements in the jet flavour identification at high transverse momentum, which increases its sensitivity relative to the previous analysis beyond that expected from the higher integrated luminosity. [Figure not available: see fulltext.]

2020, Aad, G., Abbott, B., Abbott, D. C., Abed, Abud, A., Belotskiy, K., Belyaev, N. L., Bulekov, O., Kurova, A., Ponomarenko, D., Proklova, N., Pyatiizbyantseva, D., Romaniouk, A., Smirnov, N., Smirnov, S. Yu., Smirnov, Y., Soldatov, E. Yu., Timoshenko, S., Vorobev, K., Tikhomirov, V. O., Белоцкий, Константин Михайлович, Булеков, Олег Владимирович, Курова, Анастасия Сергеевна, Пятиизбянцева, Диана Николаевна, Романюк, Анатолий Самсонович, Смирнов, Сергей Юрьевич, Смирнов, Юрий Сергеевич, Солдатов, Евгений Юрьевич, Тимошенко, Сергей Леонидович, Воробьёв, Константин Александрович, Тихомиров, Владимир Олегович

© 2020 CERN.This Letter presents a search for the production of new heavy resonances decaying into a Higgs boson and a photon using proton-proton collision data at s=13 TeV collected by the ATLAS detector at the LHC. The data correspond to an integrated luminosity of 139 fb-1. The analysis is performed by reconstructing hadronically decaying Higgs boson (H→bb¯) candidates as single large-radius jets. A novel algorithm using information about the jet constituents in the center-of-mass frame of the jet is implemented to identify the two b quarks in the single jet. No significant excess of events is observed above the expected background. Upper limits are set on the production cross-section times branching fraction for narrow spin-1 resonances decaying into a Higgs boson and a photon in the resonance mass range from 0.7 to 4 TeV, cross-section times branching fractions are excluded between 11.6 fb and 0.11 fb at a 95% confidence level.

2020, Aad, G., Abbott, B., Abbott, D. C., Abed, Abud, A., Belotskiy, K., Belyaev, N. L., Bulekov, O., Kantserov, V. A., Kurova, A., Ponomarenko, D., Proklova, N., Romaniouk, A., Smirnov, N., Smirnov, S. Y., Smirnov, Y., Soldatov, E. Y., Timoshenko, S., Vorobev, K., Tikhomirov, V. O., Белоцкий, Константин Михайлович, Булеков, Олег Владимирович, Курова, Анастасия Сергеевна, Романюк, Анатолий Самсонович, Смирнов, Сергей Юрьевич, Смирнов, Юрий Сергеевич, Солдатов, Евгений Юрьевич, Тимошенко, Сергей Леонидович, Воробьёв, Константин Александрович, Тихомиров, Владимир Олегович

© 2019 The Author(s)This letter presents a combination of searches for Higgs boson pair production using up to 36.1 fb−1 of proton–proton collision data at a centre-of-mass energy s=13 TeV recorded with the ATLAS detector at the LHC. The combination is performed using six analyses searching for Higgs boson pairs decaying into the bb¯bb¯, bb¯W+W−, bb¯τ+τ−, W+W−W+W−, bb¯γγ and W+W−γγ final states. Results are presented for non-resonant and resonant Higgs boson pair production modes. No statistically significant excess in data above the Standard Model predictions is found. The combined observed (expected) limit at 95% confidence level on the non-resonant Higgs boson pair production cross-section is 6.9 (10) times the predicted Standard Model cross-section. Limits are also set on the ratio (κλ) of the Higgs boson self-coupling to its Standard Model value. This ratio is constrained at 95% confidence level in observation (expectation) to −5.0<κλ<12.0 (−5.8<κλ<12.0). In addition, limits are set on the production of narrow scalar resonances and spin-2 Kaluza–Klein Randall–Sundrum gravitons. Exclusion regions are also provided in the parameter space of the habemus Minimal Supersymmetric Standard Model and the Electroweak Singlet Model.

2020, Aad, G., Abbott, B., Abbott, D. C., Abud, A. A., Belotskiy, K., Belyaev, N. L., Bulekov, O., Kantserov, V. A., Kurova, A., Ponomarenko, D., Proklova, N., Romaniouk, A., Smirnov, N., Smirnov, S. Y., Smirnov, Y., Soldatov, E. Y., Tikhomirov, V. O., Timoshenko, S., Vorobev, K., Белоцкий, Константин Михайлович, Булеков, Олег Владимирович, Курова, Анастасия Сергеевна, Романюк, Анатолий Самсонович, Смирнов, Сергей Юрьевич, Смирнов, Юрий Сергеевич, Солдатов, Евгений Юрьевич, Тихомиров, Владимир Олегович, Тимошенко, Сергей Леонидович, Воробьёв, Константин Александрович

A search for the direct production of the supersymmetric partners of tau-leptons (staus) in final states with two hadronically decaying tau-leptons is presented. The analysis uses a dataset of pp collisions corresponding to an integrated luminosity of 139 fb(-1), recorded with the ATLAS detector at the Large Hadron Collider at a center-of-mass energy of 13 TeV. No significant deviation from the expected Standard Model background is observed. Limits are derived in scenarios of direct production of stau pairs with each stau decaying into the stable lightest neutralino and one tau-lepton in simplified models where the two stau mass eigenstates are degenerate. Stau masses from 120 GeV to 390 GeV are excluded at 95% confidence level for a massless lightest neutralino.

2020, Aad, G., Abbott, B., Abbott, D. C., Abed, Abud, A., Belotskiy, K., Belyaev, N. L., Bulekov, O., Kantserov, V. A., Kurova, A., Ponomarenko, D., Proklova, N., Romaniouk, A., Smirnov, N., Yu, Smirnov, S., Smirnov, Y., Yu, Soldatov, E., Timoshenko, S., Vorobev, K., Tikhomirov, V. O., Белоцкий, Константин Михайлович, Булеков, Олег Владимирович, Курова, Анастасия Сергеевна, Романюк, Анатолий Самсонович, Смирнов, Сергей Юрьевич, Смирнов, Юрий Сергеевич, Солдатов, Евгений Юрьевич, Тимошенко, Сергей Леонидович, Воробьёв, Константин Александрович, Тихомиров, Владимир Олегович

© 2020 CERN for the benefit of the ATLAS collaboration.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.

2020, Aad, G., Abbott, B., Abbott, D. C., Abud, A. A., Belotskiy, K., Belyaev, N. L., Bulekov, O., Kantserov, V. A., Kurova, A., Ponomarenko, D., Proklova, N., Romaniouk, A., Smirnov, N., Smirnov, S. Y., Smirnov, Y., Soldatov, E. Y., Tikhomirov, V. O., Timoshenko, S., Vorobev, K., Белоцкий, Константин Михайлович, Булеков, Олег Владимирович, Курова, Анастасия Сергеевна, Романюк, Анатолий Самсонович, Смирнов, Сергей Юрьевич, Смирнов, Юрий Сергеевич, Солдатов, Евгений Юрьевич, Тихомиров, Владимир Олегович, Тимошенко, Сергей Леонидович, Воробьёв, Константин Александрович

The prevalence of hadronic jets at the LHC requires that a deep understanding of jet formation and structure is achieved in order to reach the highest levels of experimental and theoretical precision. There have been many measurements of jet substructure at the LHC and previous colliders, but the targeted observables mix physical effects from various origins. Based on a recent proposal to factorize physical effects, this Letter presents a double-differential cross-section measurement of the Lund jet plane using 139 fb(-1) of root s = 13 TeV proton-proton collision data collected with the ATLAS detector using jets with transverse momentum above 675 GeV. The measurement uses charged particles to achieve a fine angular resolution and is corrected for acceptance and detector effects. Several parton shower Monte Carlo models are compared with the data. No single model is found to be in agreement with the measured data across the entire plane.

2022, Semushin, A., Soldatov, E., Семушин, Артур Евгеньевич, Солдатов, Евгений Юрьевич

© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0)In this report the model-independent effective field theory phenomenology is used to parameterize the anomalous couplings in the Lagrangian with higher-dimensional operators. Setting limits on the operator's coefficients (EFT coupling constants) leads to new physics constraints. The decomposition technique of MC event generator MG5_aMC is used to produce events corresponding separate terms of the full amplitude. In the classical version of setting these limits, all background processes are considered as non-depending on coefficients. However in general case one or several backgrounds can be affected by non-zero EFT coupling constants. This report presents the way of accounting such background impact in limits setting. As an example the electroweak Zγ production is considered, since this process is extremely sensitive to anomalous quartic gauge couplings. As a result the limits on the EFT coefficients fT0 and fM0 were obtained with accounting of the possible new physics in the electroweak Wγ production background, which are 1% and 5% tighter respectively than classical ones.