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Aad, G., Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J., . . . et al., . (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.
Åpne denne publikasjonen i ny fane eller vindu >>Combination of searches for Higgs boson pairs in pp collisions at root s=13 TeV with the ATLAS detector
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2020 (engelsk)Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 800, artikkel-id 135103Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
ELSEVIER, 2020
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-266934 (URN)10.1016/j.physletb.2019.135103 (DOI)000503832500009 ()2-s2.0-85075879322 (Scopus ID)
Merknad

QC 20200130

Tilgjengelig fra: 2020-01-30 Laget: 2020-01-30 Sist oppdatert: 2020-01-30bibliografisk kontrollert
Aaboud, M., Kastanas, K. A., Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., . . . et al., . (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.
Åpne denne publikasjonen i ny fane eller vindu >>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 (engelsk)Inngår i: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 101, nr 1, artikkel-id 012002Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
AMER PHYSICAL SOC, 2020
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-266930 (URN)10.1103/PhysRevD.101.012002 (DOI)000505485600001 ()
Merknad

QC 20200131

Tilgjengelig fra: 2020-01-31 Laget: 2020-01-31 Sist oppdatert: 2020-01-31bibliografisk kontrollert
Aaboud, M., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J., . . . et al., . (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.
Åpne denne publikasjonen i ny fane eller vindu >>Measurement of J/psi production in association with a W-+/- boson with pp data at 8 TeV
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2020 (engelsk)Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 1, artikkel-id 95Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
SPRINGER, 2020
Emneord
Hadron-Hadron scattering (experiments)
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-269490 (URN)10.1007/JHEP01(2020)095 (DOI)000511676700001 ()2-s2.0-85078165339 (Scopus ID)
Merknad

QC 20200309

Tilgjengelig fra: 2020-03-09 Laget: 2020-03-09 Sist oppdatert: 2020-03-09bibliografisk kontrollert
Aad, G., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J., . . . et al., . (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.
Åpne denne publikasjonen i ny fane eller vindu >>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
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2020 (engelsk)Inngår i: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 101, nr 2, artikkel-id 024906Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
AMER PHYSICAL SOC, 2020
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-269462 (URN)10.1103/PhysRevC.101.024906 (DOI)000513213800003 ()
Merknad

QC 20200310

Tilgjengelig fra: 2020-03-10 Laget: 2020-03-10 Sist oppdatert: 2020-03-10bibliografisk kontrollert
Aad, G., Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J., . . . et al., . (2020). Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb(-1) of pp collisions at root s=13 TeV with the ATLAS experiment. Physics Letters B, 800, Article ID 135082.
Åpne denne publikasjonen i ny fane eller vindu >>Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb(-1) of pp collisions at root s=13 TeV with the ATLAS experiment
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2020 (engelsk)Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 800, artikkel-id 135082Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

A search for flavour-changing neutral current (FCNC) events via the coupling of a top quark, a photon, and an up or charm quark is presented using 81 fb(-1) of proton-proton collision data taken at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Events with a photon, an electron or muon, a b-tagged jet, and missing transverse momentum are selected. A neural network based on kinematic variables differentiates between events from signal and background processes. The data are consistent with the background-only hypothesis, and limits are set on the strength of the tq gamma coupling in an effective field theory. These are also interpreted as 95% CL upper limits on the cross section for FCNC t gamma production via a left-handed (right-handed) tu gamma coupling of 36 fb (78 fb) and on the branching ratio for t -> gamma u of 2.8 x 10(-5) (6.1 x 10(-5)). In addition, they are interpreted as 95% CL upper limits on the cross section for FCNC t gamma production via a left-handed (right-handed) tc.coupling of 40 fb (33 fb) and on the branching ratio for t -> gamma c of 22 x 10(-5) (18 x 10(-5)).

sted, utgiver, år, opplag, sider
ELSEVIER, 2020
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-266933 (URN)10.1016/j.physletb.2019.135082 (DOI)000503832500051 ()2-s2.0-85075235650 (Scopus ID)
Merknad

QC 20200130

Tilgjengelig fra: 2020-01-30 Laget: 2020-01-30 Sist oppdatert: 2020-01-30bibliografisk kontrollert
Aad, G., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J. & Zwalinski, L. (2020). Search for Magnetic Monopoles and Stable High-Electric-Charge Objects in 13 Tev Proton-Proton Collisions with the ATLAS Detector. Physical Review Letters, 124(3), Article ID 031802.
Åpne denne publikasjonen i ny fane eller vindu >>Search for Magnetic Monopoles and Stable High-Electric-Charge Objects in 13 Tev Proton-Proton Collisions with the ATLAS Detector
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2020 (engelsk)Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 124, nr 3, artikkel-id 031802Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

A search for magnetic monopoles and high-electric-charge objects is presented using 34.4 fb(-1) of 13 TeV pp collision data collected by the ATLAS detector at the LHC during 2015 and 2016. The considered signature is based upon high ionization in the transition radiation tracker of the inner detector associated with a pencil-shape energy deposit in the electromagnetic calorimeter. The data were collected by a dedicated trigger based on the tracker high-threshold hit capability. The results are interpreted in models of Drell-Yan pair production of stable particles with two spin hypotheses (0 and 1/2) and masses ranging from 200 to 4000 GeV. The search improves by approximately a factor of 5 the constraints on the direct production of magnetic monopoles carrying one or two Dirac magnetic charges and stable objects with electric charge in the range 20 <= vertical bar z vertical bar <= 60 and extends the charge range to 60 < vertical bar z vertical bar <= 100.

sted, utgiver, år, opplag, sider
American Physical Society, 2020
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-268812 (URN)10.1103/PhysRevLett.124.031802 (DOI)000509506300003 ()32031842 (PubMedID)2-s2.0-85079081039 (Scopus ID)
Merknad

QC 20200224

Tilgjengelig fra: 2020-02-24 Laget: 2020-02-24 Sist oppdatert: 2020-02-24bibliografisk kontrollert
Aad, G., Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J., . . . et al., . (2020). Searches for lepton-flavour-violating decays of the Higgs boson in root s=13 TeV pp collisions with the ATLAS detector. Physics Letters B, 800, Article ID 135069.
Åpne denne publikasjonen i ny fane eller vindu >>Searches for lepton-flavour-violating decays of the Higgs boson in root s=13 TeV pp collisions with the ATLAS detector
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2020 (engelsk)Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 800, artikkel-id 135069Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This Letter presents direct searches for lepton flavour violation in Higgs boson decays, H -> e tau and H -> mu tau, performed with the ATLAS detector at the LHC. The searches are based on a data sample of proton-proton collisions at a centre-of-mass energy root s = 13 TeV, corresponding to an integrated luminosity of 36.1 fb(-1). No significant excess is observed above the expected background from Standard Model processes. The observed (median expected) 95% confidence-level upper limits on the lepton-flavour-violating branching ratios are 0.47%(0.34(-0.10)(+0.13)%) and 0.28%(0.37(-0.10)(+0.14)%) for H -> e tau and H -> mu tau, respectively.

sted, utgiver, år, opplag, sider
ELSEVIER, 2020
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-266932 (URN)10.1016/j.physletb.2019.135069 (DOI)000503832500048 ()2-s2.0-85074945898 (Scopus ID)
Merknad

QC 20200131

Tilgjengelig fra: 2020-01-31 Laget: 2020-01-31 Sist oppdatert: 2020-01-31bibliografisk kontrollert
Aaboud, M., Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J. & Zwalinski, L. (2020). Transverse momentum and process dependent azimuthal anisotropies in root S-NN=8.16 TeV p plus Pb collisions with the ATLAS detector. European Physical Journal C, 80(1), Article ID 73.
Åpne denne publikasjonen i ny fane eller vindu >>Transverse momentum and process dependent azimuthal anisotropies in root S-NN=8.16 TeV p plus Pb collisions with the ATLAS detector
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2020 (engelsk)Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 80, nr 1, artikkel-id 73Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The azimuthal anisotropy of charged particles produced in sNN=8.16TeV p+Pb collisions is measured with the ATLAS detector at the LHC. The data correspond to an integrated luminosity of 165 nb-1 that was collected in 2016. Azimuthal anisotropy coefficients, elliptic v2 and triangular v3\, extracted using two-particle correlations with a non-flow template fit procedure, are presented as a function of particle transverse momentum (pT) between 0.5 and 50 GeV. The v2 results are also reported as a function of centrality in three different particle pTintervals. The results are reported from minimum-bias events and jet-triggered events, where two jet pT thresholds are used. The anisotropies for particles with pT less than about 2 GeV are consistent with hydrodynamic flow expectations, while the significant non-zero anisotropies for pT in the range 9-50 GeV are not explained within current theoretical frameworks. In the pTrange 2-9 GeV, the anisotropies are larger in minimum-bias than in jet-triggered events. Possible origins of these effects, such as the changing admixture of particles from hard scattering and the underlying event, are discussed.

sted, utgiver, år, opplag, sider
SPRINGER, 2020
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-270918 (URN)10.1140/epjc/s10052-020-7624-4 (DOI)000513720900001 ()2-s2.0-85079172889 (Scopus ID)
Merknad

QC 20200316

Tilgjengelig fra: 2020-03-16 Laget: 2020-03-16 Sist oppdatert: 2020-03-16bibliografisk kontrollert
Aaboud, M., Kastanas, K. A., Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., . . . Zwalinski, L. (2019). A strategy for a general search for new phenomena using data-derived signal regions and its application within the ATLAS experiment. European Physical Journal C, 79(2), Article ID 120.
Åpne denne publikasjonen i ny fane eller vindu >>A strategy for a general search for new phenomena using data-derived signal regions and its application within the ATLAS experiment
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2019 (engelsk)Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 79, nr 2, artikkel-id 120Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This paper describes a strategy for a general search used by the ATLAS Collaboration to find potential indications of new physics. Events are classified according to their final state into many event classes. For each event class an automated search algorithm tests whether the data are compatible with the Monte Carlo simulated expectation in several distributions sensitive to the effects of new physics. The significance of a deviation is quantified using pseudo-experiments. A data selection with a significant deviation defines a signal region for a dedicated follow-up analysis with an improved background expectation. The analysis of the data-derived signal regions on a new dataset allows a statistical interpretation without the large look-elsewhere effect. The sensitivity of the approach is discussed using Standard Model processes and benchmark signals of new physics. As an example, results are shown for 3.2fb-1 of proton-proton collision data at a centre-of-mass energy of 13TeV collected with the ATLAS detector at the LHC in 2015, in which more than 700 event classes and more than 105 regions have been analysed. No significant deviations are found and consequently no data-derived signal regions for a follow-up analysis have been defined.

sted, utgiver, år, opplag, sider
SPRINGER, 2019
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-244519 (URN)10.1140/epjc/s10052-019-6540-y (DOI)000457998500007 ()2-s2.0-85061187220 (Scopus ID)
Merknad

QC 20190403

Tilgjengelig fra: 2019-04-03 Laget: 2019-04-03 Sist oppdatert: 2019-04-04bibliografisk kontrollert
Aad, G., Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J., . . . et al., . (2019). ATLAS b-jet identification performance and efficiency measurement with t(t)over-bar events in pp collisions at root s=13 TeV. European Physical Journal C, 79(11), Article ID 970.
Åpne denne publikasjonen i ny fane eller vindu >>ATLAS b-jet identification performance and efficiency measurement with t(t)over-bar events in pp collisions at root s=13 TeV
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2019 (engelsk)Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 79, nr 11, artikkel-id 970Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The algorithms used by the ATLAS Collaboration during Run 2 of the Large Hadron Collider to identify jets containing b-hadrons are presented. The performance of the algorithms is evaluated in the simulation and the efficiency with which these algorithms identify jets containing b-hadrons is measured in collision data. The measurement uses a likelihood-based method in a sample highly enriched in t (t) over bar events. The topology of the t -> Wb decays is exploited to simultaneously measure both the jet flavour composition of the sample and the efficiency in a transverse momentum range from 20 to 600 GeV. The efficiency measurement is subsequently compared with that predicted by the simulation. The data used in this measurement, corresponding to a total integrated luminosity of 80.5 fb(-1), were collected in proton-proton collisions during the years 2015-2017 at a centre-of-mass energy root s = 13 TeV. By simultaneously extracting both the efficiency and jet flavour composition, this measurement significantly improves the precision compared to previous results, with uncertainties ranging from 1 to 8% depending on the jet transverse momentum.

sted, utgiver, år, opplag, sider
SPRINGER, 2019
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-266937 (URN)10.1140/epjc/s10052-019-7450-8 (DOI)000505550300004 ()2-s2.0-85075996723 (Scopus ID)
Merknad

QC 20200129

Tilgjengelig fra: 2020-01-29 Laget: 2020-01-29 Sist oppdatert: 2020-01-29bibliografisk kontrollert
Organisasjoner
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0002-0299-8236