uu.seUppsala University Publications
Change search
Link to record
Permanent link

Direct link
BETA
Publications (10 of 939) Show all publications
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
Show others...
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
Show others...
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
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
Show others...
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
Show others...
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
Show others...
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
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
Show others...
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
Aad, G., Asimakopoulou, E. M., Bergeås Kuutmann, E., Brenner, R., Ekelöf, T., Ellajosyula, V., . . . Zwalinski, L. (2020). Measurement of the azimuthal anisotropy of charged-particle production in Xe plus Xe collisions at root S-NN=5.44 TeV with the ATLAS detector. Physical Review C: Covering Nuclear Physics, 101(2), Article ID 024906.
Open this publication in new window or tab >>Measurement of the azimuthal anisotropy of charged-particle production in Xe plus Xe collisions at root S-NN=5.44 TeV with the ATLAS detector
Show others...
2020 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 101, no 2, article id 024906Article in journal (Refereed) Published
Abstract [en]

This paper describes the measurements of flow harmonics v(2)-v(6) in 3 mu b(-1) of Xe Xe collisions at root S-NN = 5.44 TeV performed using the ATLAS detector at the Large Hadron Collider (LHC). Measurements of the centrality, multiplicity, and p(T) dependence of the v(n) obtained using two-particle correlations and the scalar product technique are presented. The measurements are also performed using a template-fit procedure, which was developed to remove nonflow correlations in small collision systems. This nonflow removal is shown to have a significant influence on the measured v(n) at high p(T), especially in peripheral events. Comparisons of the measured v(n) with measurements in Pb + Pb collisions and p + Pb collisions at root S-NN = 5.02 TeV are also presented. The v(n) values in Xe + Xe collisions are observed to be larger than those in Pb + Pb collisions for n = 2, 3, and 4 in the most central events. However, with decreasing centrality or increasing harmonic order n, the v(n) values in Xe + Xe collisions become smaller than those in Pb + Pb collisions. The v(n) in Xe + Xe and Pb + Pb collisions are also compared as a function of the mean number of participating nucleons, < N-part >, and the measured charged-particle multiplicity in the detector. The v(3) values in Xe + Xe and Pb + Pb collisions are observed to be similar at the same < N-part > or multiplicity, but the other harmonics are significantly different. The ratios of the measured v(n) in Xe + Xe and Pb + Pb collisions, as a function of centrality, are also compared to theoretical calculations.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2020
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-407465 (URN)10.1103/PhysRevC.101.024906 (DOI)000513213800003 ()
Funder
Swedish Research CouncilEU, European Research CouncilEU, Horizon 2020
Note

For complete list of authors see http://dx.doi.org/10.1103/PhysRevC.101.024906

Available from: 2020-03-26 Created: 2020-03-26 Last updated: 2020-03-26Bibliographically approved
Aad, G., Asimakopoulou, E. M., Bergeås Kuutmann, E., Bokan, P., Brenner, R., Ekelöf, T., . . . Zwalinski, L. (2020). Search for direct stau production in events with two hadronic tau-leptons in root s=13 TeV pp collisions with the ATLAS detector. Physical Review D: covering particles, fields, gravitation, and cosmology, 101(3), Article ID 032009.
Open this publication in new window or tab >>Search for direct stau production in events with two hadronic tau-leptons in root s=13 TeV pp collisions with the ATLAS detector
Show others...
2020 (English)In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 101, no 3, article id 032009Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2020
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-407958 (URN)10.1103/PhysRevD.101.032009 (DOI)000517252200003 ()
Funder
Swedish Research CouncilEU, European Research CouncilEU, Horizon 2020Wallenberg Foundations
Note

For complete list of authors see http://dx.doi.org/10.1103/PhysRevD.101.032009

Available from: 2020-04-02 Created: 2020-04-02 Last updated: 2020-04-02Bibliographically approved
Aaboud, M., Asimakopoulou, E. M., Bergeås Kuutmann, E., Bokan, P., Brenner, R., Ekelöf, T., . . . Zwalinski, L. (2020). Search for displaced vertices of oppositely charged leptons from decays of long-lived particles in pp collisions at root s=13 TeV with the ATLAS detector. Physics Letters B, 801, Article ID 135114.
Open this publication in new window or tab >>Search for displaced vertices of oppositely charged leptons from decays of long-lived particles in pp collisions at root s=13 TeV with the ATLAS detector
Show others...
2020 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 801, article id 135114Article in journal (Refereed) Published
Abstract [en]

A search for long-lived particles decaying into an oppositely charged lepton pair, mu mu, ee, or e mu, is presented using 32.8 fb(-1) of pp collision data collected at root s = 13 TeV by the ATLAS detector at the LHC. Candidate leptons are required to form a vertex, within the inner tracking volume of ATLAS, displaced from the primary pp interaction region. No lepton pairs with an invariant mass greater than 12 GeV are observed, consistent with the background expectations derived from data. The detection efficiencies for generic resonances with lifetimes (c tau) of 100-1000 mm decaying into a dilepton pair with masses between 0.1-1.0 TeV are presented as a function of p(T) and decay radius of the resonances to allow the extraction of upper limits on the cross sections for theoretical models. The result is also interpreted in a supersymmetric model in which the lightest neutralino, produced via squark-antisquark production, decays into l(+) l'(-) nu(l, l' = e, mu) with a finite lifetime due to the presence of R-parity violating couplings. Cross-section limits are presented for specific squark and neutralino masses. For a 700 GeV squark, neutralinos with masses of 50-500 GeV and mean proper lifetimes corresponding to c tau values between 1 mm to 6 m are excluded. For a 1.6 TeV squark, c tau values between 3 mm to 1 m are excluded for 1.3 TeV neutralinos.

Place, publisher, year, edition, pages
ELSEVIER, 2020
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-406221 (URN)10.1016/j.physletb.2019.135114 (DOI)000508018500036 ()
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.2019.135114

Available from: 2020-03-09 Created: 2020-03-09 Last updated: 2020-03-09Bibliographically approved
Aaboud, M., Asimakopoulou, E. M., Bergeås Kuutmann, E., Bokan, P., Brenner, R., Ekelöf, T., . . . Zwalinski, L. (2020). Search for electroweak production of charginos and sleptons decaying into final states with two leptons and missing transverse momentum in root s=13 TeV pp collisions using the ATLAS detector. European Physical Journal C, 80(2), Article ID 123.
Open this publication in new window or tab >>Search for electroweak production of charginos and sleptons decaying into final states with two leptons and missing transverse momentum in root s=13 TeV pp collisions using the ATLAS detector
Show others...
2020 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 80, no 2, article id 123Article in journal (Refereed) Published
Abstract [en]

A search for the electroweak production of charginos and sleptons decaying into final states with two electrons or muons is presented. The analysis is based on 139 fb(-1) of proton-proton collisions recorded by the ATLAS detector at the Large Hadron Collider at v s = 13 TeV. Three R-parity-conserving scenarios where the lightest neutralino is the lightest supersymmetric particle are considered: the production of chargino pairs with decays via eitherW bosons or sleptons, and the direct production of slepton pairs. The analysis is optimised for the first of these scenarios, but the results are also interpreted in the others. No significant deviations from the Standard Model expectations are observed and limits at 95% confidence level are set on the masses of relevant supersymmetric particles in each of the scenarios. For a massless lightest neutralino, masses up to 420 GeV are excluded for the production of the lightest-chargino pairs assuming W-boson-mediated decays and up to 1 TeV for slepton-mediated decays, whereas for slepton-pair production masses up to 700 GeV are excluded assuming three generations of mass-degenerate sleptons.

Place, publisher, year, edition, pages
SPRINGER, 2020
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-407957 (URN)10.1140/epjc/s10052-019-7594-6 (DOI)000515792500002 ()
Funder
Swedish Research CouncilEU, European Research CouncilEU, Horizon 2020Wallenberg Foundations
Note

For complete list of authors see http://dx.doi.org/10.1140/epjc/s10052-019-7594-6

Available from: 2020-04-03 Created: 2020-04-03 Last updated: 2020-04-03Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-8204-4124

Search in DiVA

Show all publications