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Смирнов, Сергей Юрьевич

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Цель ИЯФиТ и стратегия развития - создание и развитие научно-образовательного центра мирового уровня в области ядерной физики и технологий, радиационного материаловедения, физики элементарных частиц, астрофизики и космофизики.

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Смирнов

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Сергей Юрьевич

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Только метаданные
Measurement of angular and momentum distributions of charged particles within and around jets in Pb plus Pb and pp collisions at root s(NN)=5.02 TeV with ATLAS at the LHC
(2019) Puri, A.; Aaboud, M.; Aad, G.; Abbott, B.; Belotskiy, K.; Belyaev, N. L.; Bulekov, O.; Kantserov, V. A.; Ponomarenko, D.; Proklova, N.; Romaniouk, A.; Shulga, E.; Smimov, N.; Smirnov, S. Y.; Smirnov, Y.; Soldatov, E. Y.; Tikhomirov, V. O.; Timoshenko, S.; Vorobev, K.; Белоцкий, Константин Михайлович; Булеков, Олег Владимирович; Романюк, Анатолий Самсонович; Смирнов, Сергей Юрьевич; Смирнов, Юрий Сергеевич; Солдатов, Евгений Юрьевич; Тихомиров, Владимир Олегович; Тимошенко, Сергей Леонидович; Воробьёв, Константин Александрович
Studies of the fragmentation of jets into charged particles in heavy-ion collisions can help in understanding the mechanism of jet quenching by the hot and dense QCD matter created in such collisions, the quark-gluon plasma. These proceedings present a measurement of the angular distribution of charged particles around the jet axis in root s(NN) = 5.02 TeV Pb+Pb and pp collisions, done using the ATLAS detector at the LHC. The measurement is performed inside jets reconstructed with the anti-k(t) algorithm with radius parameter R = 0.4, and is extended to regions outside the jet cone. Results are presented as a function of Pb+Pb collision centrality, and both jet and charged-particle transverse momenta.
Только метаданные
Measurement of flow harmonics correlations with mean transverse momentum in lead–lead and proton–lead collisions at √sNN=5.02TeV with the ATLAS detector
(2019) 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.; 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, CERN for the benefit of the ATLAS collaboration.To assess the properties of the quark–gluon plasma formed in ultrarelativistic ion collisions, the ATLAS experiment at the LHC measures a correlation between the mean transverse momentum and the flow harmonics. The analysis uses data samples of lead–lead and proton–lead collisions obtained at the centre-of-mass energy per nucleon pair of 5.02 TeV, corresponding to total integrated luminosities of 22μb-1 and 28nb-1, respectively. The measurement is performed using a modified Pearson correlation coefficient with the charged-particle tracks on an event-by-event basis. The modified Pearson correlation coefficients for the 2nd-, 3rd-, and 4th-order flow harmonics are measured in the lead–lead collisions as a function of event centrality quantified as the number of charged particles or the number of nucleons participating in the collision. The measurements are performed for several intervals of the charged-particle transverse momentum. The correlation coefficients for all studied harmonics exhibit a strong centrality evolution, which only weakly depends on the charged-particle momentum range. In the proton–lead collisions, the modified Pearson correlation coefficient measured for the 2nd-order flow harmonics shows only weak centrality dependence. The lead-lead data is qualitatively described by the predictions based on the hydrodynamical model.
Только метаданные
Measurement of KS0 and Λ production in tt¯ dileptonic events in pp collisions at √s= 7 TeV with the ATLAS detector
(2019) Aad, G.; Abbott, B.; Abbott, D. C.; Abdinov, O.; 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
© 2019, CERN for the benefit of the ATLAS collaboration.Measurements of KS0 and Λ production in tt¯ final states have been performed. They are based on a data sample with integrated luminosity of 4.6 fb - 1 from proton–proton collisions at a centre-of-mass energy of 7 TeV, collected in 2011 with the ATLAS detector at the Large Hadron Collider. Neutral strange particles are separated into three classes, depending on whether they are contained in a jet, with or without a b-tag, or not associated with a selected jet. The aim is to look for differences in their main kinematic distributions. A comparison of data with several Monte Carlo simulations using different hadronisation and fragmentation schemes, colour reconnection models and different tunes for the underlying event has been made. The production of neutral strange particles in tt¯ dileptonic events is found to be well described by current Monte Carlo models for KS0 and Λ production within jets, but not for those produced outside jets.
Только метаданные
Measurement of the flow harmonic correlations in pp, p plus Pb and low multiplicity Pb plus Pb collisions with the ATLAS detector at the LHC
(2019) Derendarz, D.; Aaboud, M.; Aad, G.; Abbott, B.; Belotskiy, K.; Belyaev, N. L.; Bulekov, O.; Kantserov, V. 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; Романюк, Анатолий Самсонович; Смирнов, Сергей Юрьевич; Смирнов, Юрий Сергеевич; Солдатов, Евгений Юрьевич; Тихомиров, Владимир Олегович; Тимошенко, Сергей Леонидович; Воробьёв, Константин Александрович
Recent measurements of the correlations between flow harmonics obtained using four-particle symmetric cumulants and three-particle asymmetric cumulants with the ATLAS detector at the LHC are described. The data sets of pp, p+Pb and peripheral Pb+Pb collisions at various energies are analyzed, aiming to probe the long-range collective nature of multi-particle production in small systems. The sensitivity of the standard cumulant method to non-flow correlations is investigated by introducing the subevents method. A systematic reduction of non-flow effects is observed when using the two-subevent method. Further reduction is observed with the three-subevent method that is consistent with the results obtained with the four-subevent one. A negative correlation between v(2) and v(3) and a positive correlation between v(2) and v(4), for all studied collision systems and over full multiplicity range, is observed. The correlation strength computed as symmetric cumulants normalized by the < v(n)(2)> is similar for all collision systems and weakly depends on multiplicity. These measurements provide new evidence for long-range multi-particle collectivity in small collision systems and quantify the nature of its event-by-event fluctuations.
Только метаданные
Search for Heavy Resonances Decaying into a Photon and a Hadronically Decaying Higgs Boson in pp Collisions at s =13 TeV with the ATLAS Detector
(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.
Только метаданные
Search for new phenomena in final states with large jet multiplicities and missing transverse momentum using root s=13 TeV proton-proton collisions recorded by ATLAS in Run 2 of the LHCY
(2020) Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.; Belotskiy, K.; Belyaev, N. L.; Bulekov, O.; 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.; Pyatiizbyantseva, D.; 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; Пятиизбянцева, Диана Николаевна
Results of a search for new particles decaying into eight or more jets and moderate missing transverse momentum are presented. The analysis uses 139 fb(-1) of proton-proton collision data at root s = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider between 2015 and 2018. The selection rejects events containing isolated electrons or muons, and makes requirements according to the number of b-tagged jets and the scalar sum of masses of large-radius jets. The search extends previous analyses both in using a larger dataset and by employing improved jet and missing transverse momentum reconstruction methods which more cleanly separate signal from background processes. No evidence for physics beyond the Standard Model is found. The results are interpreted in the context of supersymmetry-inspired simplified models, significantly extending the limits on the gluino mass in those models. In particular, limits on the gluino mass are set at 2 TeV when the lightest neutralino is nearly massless in a model assuming a two-step cascade decay via the lightest chargino and second-lightest neutralino.
Только метаданные
Charged-hadron suppression in Pb plus Pb and Xe plus Xe collisions measured with the ATLAS detector
(2019) Balek, P.; Aaboud, M.; Aad, G.; Abbott, B.; Belotskiy, K.; Belyaev, N. L.; Bulekov, O.; Kantserov, V. 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; Романюк, Анатолий Самсонович; Смирнов, Сергей Юрьевич; Смирнов, Юрий Сергеевич; Солдатов, Евгений Юрьевич; Тихомиров, Владимир Олегович; Тимошенко, Сергей Леонидович; Воробьёв, Константин Александрович
The ATLAS detector at the LHC recorded 0.49 nb(-1) of Pb+Pb collisions and 25 of pp(-1) collisions, both at the center-of-mass energy 5.02 TeV per nucleon pair. Recently, ATLAS also recorded 30 mu b(-1) of Xe+Xe collisions at the center-of-mass energy 5.44 TeV, which provides a new opportunity to study the system-size dependence of the charged-hadron production in heavy-ion collisions. The large acceptance of the ATLAS detector allows to measure the spectra of charged hadrons in a wide range of pseudorapidity and transverse momentum. The nuclear modification factors R-AA are constructed as a ratio of the spectra measured in Pb+Pb or Xe+Xe collisions to that measured in pp collisions. The R-AA obtained in the two systems are presented for different centrality intervals and the results are discussed.
Только метаданные
Search for long-lived, massive particles in events with a displaced vertex and a muon with large impact parameter in pp collisions at root s=13 TeV with the ATLAS detector
(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 long-lived particles decaying into hadrons and at least one muon is presented. The analysis selects events that pass a muon or missing-transverse-momentum trigger and contain a displaced muon track and a displaced vertex. The analyzed dataset of proton-proton collisions at root s = 13 TeV was collected with the ATLAS detector and corresponds to 136 fb(-1). The search employs dedicated reconstruction techniques that significantly increase the sensitivity to long-lived particle decays that occur in the ATLAS inner detector. Background estimates for Standard Model processes and instrumental effects are extracted from data. The observed event yields are compatible with those expected from background processes. The results are presented as limits at 95% confidence level on model-independent cross sections for processes beyond the Standard Model, and interpreted as exclusion limits in scenarios with pair production of long-lived top squarks that decay via a small R-parity-violating coupling into a quark and a muon. Top squarks with masses up to 1.7 TeV are excluded for a lifetime of 0.1 ns, and masses below 1.3 TeV are excluded for lifetimes between 0.01 ns and 30 ns.
Только метаданные
Measurements of top-quark pair spin correlations in the eμ channel at √s=13 TeV using pp collisions in the ATLAS detector
(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.; 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
© 2020, CERN for the benefit of the ATLAS Collaboration.A measurement of observables sensitive to spin correlations in tt¯ production is presented, using 36.1 fb - 1 of pp collision data at s=13 TeV recorded with the ATLAS detector at the Large Hadron Collider. Differential cross-sections are measured in events with exactly one electron and one muon with opposite-sign electric charge as a function of the azimuthal opening angle and the absolute difference in pseudorapidity between the electron and muon candidates in the laboratory frame. The azimuthal opening angle is also measured as a function of the invariant mass of the tt¯ system. The measured differential cross-sections are compared to predictions by several NLO Monte Carlo generators and fixed-order calculations. The observed degree of spin correlation is somewhat higher than predicted by the generators used. The data are consistent with the prediction of one of the fixed-order calculations at NLO, but agree less well with higher-order predictions. Using these leptonic observables, a search is performed for pair production of supersymmetric top squarks decaying into Standard Model top quarks and light neutralinos. Top squark masses between 170 and 230 GeV are largely excluded at the 95% confidence level for kinematically allowed values of the neutralino mass.
Только метаданные
Search for Higgs Boson Decays into a Z Boson and a Light Hadronically Decaying Resonance Using 13 TeV pp Collision Data from the ATLAS Detector
(2020) Aaboud, M.; Aad, G.; Abbott, B.; Abbott, D. C.; Belotskiy, K.; Belyaev, N. L.; Bulekov, O.; 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.; Pyatiizbyantseva, D.; 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; Пятиизбянцева, Диана Николаевна
A search for Higgs boson decays into a Z boson and a light resonance in two-lepton plus jet events is performed, using a pp collision dataset with an integrated luminosity of 139 fb(-1) collected at root s = 13 TeV by the ATLAS experiment at the CERN LHC. The resonance considered is a light boson with a mass below 4 GeV from a possible extended scalar sector or a charmonium state. Multivariate discriminants are used for the event selection and for evaluating the mass of the light resonance. No excess of events above the expected background is found. Observed (expected) 95% confidence-level upper limits are set on the Riggs boson production cross section times branching fraction to a Z boson and the signal resonance, with values in the range 17-340 pb (16(-5)(+6)-320(-90)(+130) pb) for the different light spin-0 boson mass and branching fraction hypotheses, and with values of 110 and 100 pb (100(-30)(+40) and 100(-30)(+40) pb) for the eta(c) and J/psi hypotheses, respectively.