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Aad, G., Asimakopoulou, E. M., Bergeås Kuutmann, E., Bokan, P., Brenner, R., Ekelöf, T., . . . Zwalinski, L. (2020). Combination of searches for Higgs boson pairs in pp collisions at root s=13 TeV with the ATLAS detector. Physics Letters B, 800, Article ID 135103.
Open this publication in new window or tab >>Combination of searches for Higgs boson pairs in pp collisions at root s=13 TeV with the ATLAS detector
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2020 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 800, article id 135103Article in journal (Refereed) Published
Abstract [en]

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 root 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 b (b) over barb (b) over bar, b (b) over barW(+)W(-), b (b) over bar tau(+)tau(-), W+W-W+W-, b (b) over bar gamma gamma and W+W-gamma gamma 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 (kappa(lambda)) 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 < kappa(lambda) < 12.0 (-5.8 < kappa(lambda) < 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. 

Place, publisher, year, edition, pages
ELSEVIER, 2020
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-403504 (URN)10.1016/j.physletb.2019.135103 (DOI)000503832500009 ()
Funder
Swedish Research CouncilEU, European Research CouncilEU, Horizon 2020Wallenberg Foundations
Note

For complete list of authors see http://dx.doi.org/10.1016/j.physletb.2019.135103

Available from: 2020-01-29 Created: 2020-01-29 Last updated: 2020-01-29Bibliographically approved
Aaboud, M., Asimakopoulou, E. M., Bergeås Kuutmann, E., Bokan, P., Brenner, R., Ekelöf, T., . . . Zwalinski, L. (2020). Combined measurements of Higgs boson production and decay using up to 80 fb(-1) of proton-proton collision data at root S=13 TeV collected with the ATLAS experiment. Physical Review D: covering particles, fields, gravitation, and cosmology, 101(1), Article ID 012002.
Open this publication in new window or tab >>Combined measurements of Higgs boson production and decay using up to 80 fb(-1) of proton-proton collision data at root S=13 TeV collected with the ATLAS experiment
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2020 (English)In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 101, no 1, article id 012002Article in journal (Refereed) Published
Abstract [en]

Combined measurements of Higgs boson production cross sections and branching fractions arc presented. The combination is based on the analyses of the Higgs boson decay modes H -> gamma gamma, ZZ*, WW*, tau tau, b (b) over bar, mu mu, searches for decays into invisible final states, and on measurements of off-shell Higgs boson production. Up to 79.8 fb(-1) of proton-proton collision data collected at root S = 13 TeV with the ATLAS detector are used. Results are presented for the gluon-gluon fusion and vector-boson fusion processes, and for associated production with vector bosons or top-quarks. The global signal strength is determined to be mu = 1.11(-0.08)(+0.09). The combined measurement yields an observed (expected) significance for the vector-boson fusion production process of 6.5 sigma (5.3 sigma). Measurements in kinematic regions defined within the simplified template cross section framework are also shown. The results are interpreted in terms of modifiers applied to the Standard Model couplings of the Higgs boson to other particles, and are used to set exclusion limits on parameters in two-Higgs-doublet models and in the simplified minimal supersynunetric Standard Model. No significant deviations from Standard Model predictions are observed.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2020
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-403500 (URN)10.1103/PhysRevD.101.012002 (DOI)000505485600001 ()
Funder
Swedish Research CouncilEU, European Research CouncilEU, Horizon 2020Wallenberg Foundations
Note

For complete list of authors see http://dx.doi.org/10.1103/PhysRevD.101.012002

Available from: 2020-01-29 Created: 2020-01-29 Last updated: 2020-01-29Bibliographically approved
Aad, G., Asimakopoulou, E. M., Bergeås Kuutmann, E., Bokan, P., Brenner, R., Ekelöf, T., . . . Zwalinski, L. (2020). Evidence for electroweak production of two jets in association with a Zγ pair in pp collisions at √S=13 TeV with the ATLAS detector. Physics Letters B, 803, Article ID 135341.
Open this publication in new window or tab >>Evidence for electroweak production of two jets in association with a Zγ pair in pp collisions at √S=13 TeV with the ATLAS detector
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2020 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 803, article id 135341Article in journal (Refereed) Published
Abstract [en]

Evidence for electroweak production of two jets in association with a Z gamma pair in root s = 13 TeV proton-proton collisions at the Large Hadron Collider is presented. The analysis uses data collected by the ATLAS detector in 2015 and 2016 that corresponds to an integrated luminosity of 36.1 fb(-1). Events that contain a Z boson candidate decaying leptonically into either e(+)e(-) or mu(+)mu(-), a photon, and two jets are selected. The electroweak component is measured with observed and expected significances of 4.1 standard deviations. The fiducial cross-section for electroweak production is measured to be sigma(Z gamma jj-Ew) = 7.8 +/- 2.0 fb, in good agreement with the Standard Model prediction.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-409719 (URN)10.1016/j.physletb.2020.135341 (DOI)000521730300023 ()
Funder
Swedish Research CouncilEU, European Research CouncilEU, Horizon 2020
Note

For complete list of authors see http://dx.doi.org/10.1016/j.physletb.2020.135341

Available from: 2020-04-27 Created: 2020-04-27 Last updated: 2020-04-27Bibliographically approved
Aaboud, M., Asimakopoulou, E. M., Bergeås Kuutmann, E., Bokan, P., Brenner, R., Ekelöf, T., . . . Zwalinski, L. (2020). Fluctuations of anisotropic flow in Pb plus Pb collisions at root s(NN)=5.02 TeV with the ATLAS detector. Journal of High Energy Physics (JHEP) (1), Article ID 51.
Open this publication in new window or tab >>Fluctuations of anisotropic flow in Pb plus Pb collisions at root s(NN)=5.02 TeV with the ATLAS detector
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2020 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 1, article id 51Article in journal (Refereed) Published
Abstract [en]

Multi-particle azimuthal cumulants are measured as a function of centrality and transverse momentum using 470 mu b(-1) of Pb+Pb collisions at root s(NN) = 5.02TeV with the ATLAS detector at the LHC. These cumulants provide information on the event-by-event fluctuations of harmonic flow coefficients v(n) and correlated fluctuations between two harmonics v(n) and v(m). For the first time, a non-zero four-particle cumulant is observed for dipolar flow, v(1). The four-particle cumulants for elliptic flow, v(2), and triangular flow, v(3), exhibit a strong centrality dependence and change sign in ultra-central collisions. This sign change is consistent with significant non-Gaussian fluctuations in v(2) and v(3). The four-particle cumulant for quadrangular flow, v(4), is found to change sign in mid-central collisions. Correlations between two harmonics are studied with three- and four-particle mixed-harmonic cumulants, which indicate an anti-correlation between v(2) and v(3), and a positive correlation between v(2) and v(4). These correlations decrease in strength towards central collisions and either approach zero or change sign in ultra-central collisions. To investigate the possible flow fluctuations arising from intrinsic centrality or volume fluctuations, the results are compared between two different event classes used for centrality definitions. In peripheral and mid-central collisions where the cumulant signals are large, only small differences are observed. In ultra-central collisions, the differences are much larger and transverse momentum dependent. These results provide new information to disentangle flow fluctuations from the initial and final states, as well as new insights on the influence of centrality fluctuations.

Place, publisher, year, edition, pages
SPRINGER, 2020
Keywords
Hadron-Hadron scattering (experiments), Heavy-ion collision, Collective flow, Event-by-event fluctuation, Particle correlations and fluctuations
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-407983 (URN)10.1007/JHEP01(2020)051 (DOI)000511969100001 ()
Funder
Swedish Research CouncilEU, European Research CouncilEU, Horizon 2020Wallenberg Foundations
Note

For complete list of authors see http://dx.doi.org/10.1007/JHEP01(2020)051

Available from: 2020-04-03 Created: 2020-04-03 Last updated: 2020-04-03Bibliographically approved
Aaboud, M., Asimakopoulou, E. M., Bergeås Kuutmann, E., Bokan, P., Brenner, R., Ekelöf, T., . . . Zwalinski, L. (2020). Measurement of Azimuthal Anisotropy of Muons from Charm and Bottom Hadrons in pp Collisions at root s=13 TeV with the ATLAS Detector. Physical Review Letters, 124(8), Article ID 082301.
Open this publication in new window or tab >>Measurement of Azimuthal Anisotropy of Muons from Charm and Bottom Hadrons in pp Collisions at root s=13 TeV with the ATLAS Detector
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2020 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 124, no 8, article id 082301Article in journal (Refereed) Published
Abstract [en]

The elliptic flow of muons from the decay of charm and bottom hadrons is measured in pp collisions at root s = 13 TeV using a data sample with an integrated luminosity of 150 pb(-1) recorded by the ATLAS detector at the LHC. The muons from heavy-flavor decay are separated from light-hadron decay muons using momentum imbalance between the tracking and muon spectrometers. The heavy-flavor decay muons are further separated into those from charm decay and those from bottom decay using the distance-of-closest-approach to the collision vertex. The measurement is performed for muons in the transverse momentum range 4-7 GeV and pseudorapidity range vertical bar eta vertical bar < 2.4. A significant nonzero elliptic anisotropy coefficient nu(2) is observed for muons from charm decays, while the nu(2) value for muons from bottom decays is consistent with zero within uncertainties.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2020
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-407982 (URN)10.1103/PhysRevLett.124.082301 (DOI)000517288800010 ()32167369 (PubMedID)
Funder
Swedish Research CouncilEU, European Research CouncilEU, Horizon 2020Wallenberg Foundations
Note

For complete list of authors see http://dx.doi.org/10.1103/PhysRevLett.124.082301

Available from: 2020-04-03 Created: 2020-04-03 Last updated: 2020-04-03Bibliographically approved
Aad, G., Asimakopoulou, E. M., Bergeås Kuutmann, E., Bokan, P., Brenner, R., Ekelöf, T., . . . Zwalinski, L. (2020). Measurement of differential cross sections for single diffractive dissociation in root s=8 TeV pp collisions using the ATLAS ALFA spectrometer. Journal of High Energy Physics (JHEP) (2), Article ID 42.
Open this publication in new window or tab >>Measurement of differential cross sections for single diffractive dissociation in root s=8 TeV pp collisions using the ATLAS ALFA spectrometer
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2020 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 2, article id 42Article in journal (Refereed) Published
Abstract [en]

A dedicated sample of Large Hadron Collider proton-proton collision data at centre-of-mass energy s= 8 TeV is used to study inclusive single diffractive dissociation, pp -> X p. The intact final-state proton is reconstructed in the ATLAS ALFA forward spectrometer, while charged particles from the dissociated system X are measured in the central detector components. The fiducial range of the measurement is -4.0 < log(10)xi < -1.6 and 0.016 < |t| < 0.43 GeV2, where xi is the proton fractional energy loss and t is the squared four-momentum transfer. The total cross section integrated across the fiducial range is 1.59 +/- 0.13 mb. Cross sections are also measured differentially as functions of xi, t, and increment eta, a variable that characterises the rapidity gap separating the proton and the system X . The data are consistent with an exponential t dependence, d sigma/dt proportional to e(Bt) with slope parameter B = 7.65 +/- 0.34 GeV-2. Interpreted in the framework of triple Regge phenomenology, the xi dependence leads to a pomeron intercept of alpha(0) = 1.07 +/- 0.09.

Place, publisher, year, edition, pages
SPRINGER, 2020
Keywords
Diffraction, Forward physics, Hadron-Hadron scattering (experiments), QCD
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-407654 (URN)10.1007/JHEP02(2020)042 (DOI)000515812400002 ()
Funder
Swedish Research CouncilEU, European Research CouncilEU, Horizon 2020Wallenberg Foundations
Note

For complete list of authors see http://dx.doi.org/10.1007/JHEP02(2020)042

Available from: 2020-03-31 Created: 2020-03-31 Last updated: 2020-03-31Bibliographically approved
Aad, G., Asimakopoulou, E. M., Bergeås Kuutmann, E., Bokan, P., Brenner, R., Ekelöf, T., . . . Zwalinski, L. (2020). Measurement of isolated-photon plus two-jet production in pp collisions at √s=13 TeV with the ATLAS detector. Journal of High Energy Physics (JHEP) (3), Article ID 179.
Open this publication in new window or tab >>Measurement of isolated-photon plus two-jet production in pp collisions at √s=13 TeV with the ATLAS detector
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2020 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 3, article id 179Article in journal (Refereed) Published
Abstract [en]

The dynamics of isolated-photon plus two-jet production in pp collisions at a centre-of-mass energy of 13 TeV are studied with the ATLAS detector at the LHC using a dataset corresponding to an integrated luminosity of 36.1 fb(-1). Cross sections are measured as functions of a variety of observables, including angular correlations and invariant masses of the objects in the final state, gamma + jet + jet. Measurements are also performed in phase-space regions enriched in each of the two underlying physical mechanisms, namely direct and fragmentation processes. The measurements cover the range of photon (jet) transverse momenta from 150 GeV (100 GeV) to 2 TeV. The tree-level plus parton-shower predictions from Sherpa and Pythia as well as the next-to-leading-order QCD predictions from Sherpa are compared with the measurements. The next-to-leading-order QCD predictions describe the data adequately in shape and normalisation except for regions of phase space such as those with high values of the invariant mass or rapidity separation of the two jets, where the predictions overestimate the data.

Keywords
Hadron-Hadron scattering (experiments), Hard scattering, Jets, Photon production
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-411005 (URN)10.1007/JHEP03(2020)179 (DOI)000524515700001 ()
Funder
Swedish Research CouncilEU, European Research CouncilEU, Horizon 2020
Note

For complete list of authors see http://dx.doi.org/10.1007/JHEP03(2020)179

Available from: 2020-05-26 Created: 2020-05-26 Last updated: 2020-05-26Bibliographically approved
Aaboud, M., Asimakopoulou, E. M., Bergeås Kuutmann, E., Bokan, P., Brenner, R., Ekelöf, T., . . . Zwalinski, L. (2020). Measurement of J/psi production in association with a W-+/- boson with pp data at 8 TeV. Journal of High Energy Physics (JHEP) (1), Article ID 95.
Open this publication in new window or tab >>Measurement of J/psi production in association with a W-+/- boson with pp data at 8 TeV
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2020 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 1, article id 95Article in journal (Refereed) Published
Abstract [en]

A measurement of the production of a prompt J/psi meson in association with a W-+/- boson with W-+/- -> mu nu and J/psi -> mu(+)mu(-) is presented for J/psi transverse momenta in the range 8.5-150 GeV and rapidity |y(J/psi)| < 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/psi plus W-+/- cross-section to the inclusive W-+/- cross-section is presented as a differential measurement as a function of J/psi transverse momenta and compared with theoretical predictions using different double-parton-scattering cross-sections.

Place, publisher, year, edition, pages
SPRINGER, 2020
Keywords
Hadron-Hadron scattering (experiments)
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-407462 (URN)10.1007/JHEP01(2020)095 (DOI)000511676700001 ()
Funder
Swedish Research CouncilEU, European Research CouncilEU, Horizon 2020
Note

For complete list of authors see http://dx.doi.org/10.1007/JHEP01(2020)095

Available from: 2020-03-26 Created: 2020-03-26 Last updated: 2020-03-26Bibliographically approved
Aaboud, M., Asimakopoulou, E. M., Bergeås Kuutmann, E., Bokan, P., Brenner, R., Ekelöf, T., . . . Zwalinski, L. (2020). Measurement of long-range two-particle azimuthal correlations in Z-boson tagged pp collisions at root s=8 and 13 TeV. European Physical Journal C, 80(1), Article ID 64.
Open this publication in new window or tab >>Measurement of long-range two-particle azimuthal correlations in Z-boson tagged pp collisions at root s=8 and 13 TeV
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2020 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 80, no 1, article id 64Article in journal (Refereed) Published
Abstract [en]

Results are presented from the measurement by ATLAS of long-range (|Delta eta|>2) dihadron angular correlations in root s=8 and 13 TeV pp collisions containing a Z boson. The analysis is performed using 19.4 fb-1 of root s=8 TeV data recorded during Run 1 of the LHC and 36.1 fb-1 of root s=13 TeV data recorded during Run 2. Two-particle correlation functions are measured as a function of relative azimuthal angle over the relative pseudorapidity range 2<|Delta eta|<5 for different intervals of charged-particle multiplicity and transverse momentum. The measurements are corrected for the presence of background charged particles generated by collisions that occur during one passage of two colliding proton bunches in the LHC. Contributions to the two-particle correlation functions from hard processes are removed using a template-fitting procedure. Sinusoidal modulation in the correlation functions is observed and quantified by the second Fourier coefficient of the correlation function, v2,2, which in turn is used to obtain the single-particle anisotropy coefficient v2. The v2 values in the Z-tagged events, integrated over 0.5<pT<5 GeV, are found to be independent of multiplicity and <mml:msqrt>s</mml:msqrt>, and consistent within uncertainties with previous measurements in inclusive pp collisions. As a function of charged-particle pT, the Z-tagged and inclusive v2 values are consistent within uncertainties for pT<3 GeV.

Place, publisher, year, edition, pages
SPRINGER, 2020
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-409803 (URN)10.1140/epjc/s10052-020-7606-6 (DOI)000521222100003 ()
Funder
Swedish Research CouncilEU, European Research CouncilEU, Horizon 2020Wallenberg Foundations
Note

For complete list of authors see http://dx.doi.org/10.1140/epjc/s10052-020-7606-6

Available from: 2020-05-04 Created: 2020-05-04 Last updated: 2020-05-04Bibliographically approved
Aad, G., Asimakopoulou, E. M., Bergeås Kuutmann, E., Bokan, P., Brenner, R., Ekelöf, T., . . . Zwalinski, L. (2020). Measurement of soft-drop jet observables in pp collisions with the ATLAS detector at root s=13 TeV. Physical Review D: covering particles, fields, gravitation, and cosmology, 101(5), Article ID 052007.
Open this publication in new window or tab >>Measurement of soft-drop jet observables in pp collisions with the ATLAS detector at root s=13 TeV
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2020 (English)In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 101, no 5, article id 052007Article in journal (Refereed) Published
Abstract [en]

Jet substructure quantities are measured using jets groomed with the soft-drop grooming procedure in dijet events from 32.9 fb(-1) of pp collisions collected with the ATLAS detector at root s = 13 TeV. These observables are sensitive to a wide range of QCD phenomena. Some observables, such as the jet mass and opening angle between the two subjets which pass the soft-drop condition, can be described by a high-order (resummed) series in the strong coupling constant alpha(s). Other observables, such as the momentum sharing between the two subjets, are nearly independent of alpha(s). These observables can be constructed using all interacting particles or using only charged particles reconstructed in the inner tracking detectors. Track-based versions of these observables are not collinear safe, but are measured more precisely, and universal nonperturbative functions can absorb the collinear singularities. The unfolded data are directly compared with QCD calculations and hadron-level Monte Carlo simulations. The measurements are performed in different pseudorapidity regions, which are then used to extract quark and gluon jet shapes using the predicted quark and gluon fractions in each region. All of the parton shower and analytical calculations provide an excellent description of the data in most regions of phase space.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2020
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-409805 (URN)10.1103/PhysRevD.101.052007 (DOI)000519886300002 ()
Funder
Swedish Research CouncilEU, European Research CouncilEU, Horizon 2020Wallenberg Foundations
Note

For complete list of authors see http://dx.doi.org/10.1103/PhysRevD.101.052007

Available from: 2020-05-04 Created: 2020-05-04 Last updated: 2020-05-04Bibliographically approved
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