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Publications (10 of 915) Show all publications
Aaboud, M., Kastanas, K. A., Lund-Jensen, B., Ripellino, G., Sidebo, P. E., Strandberg, J., . . . et.al., . (2018). A search for pair-produced resonances in four-jet final states at root s=13 TeV with the ATLAS detector. European Physical Journal C, 78(3)
Open this publication in new window or tab >>A search for pair-produced resonances in four-jet final states at root s=13 TeV with the ATLAS detector
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2018 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 78, no 3Article in journal (Refereed) Published
Abstract [en]

A search for massive coloured resonances which are pair-produced and decay into two jets is presented. The analysis uses 36.7 fb(-1) of root s = 13 TeV pp collision data recorded by the ATLAS experiment at the LHC in 2015 and 2016. No significant deviation from the background prediction is observed. Results are interpreted in a SUSY simplified model where the lightest supersymmetric particle is the top squark, (t) over tilde, which decays promptly into two quarks through R-parity-violating couplings. Top squarks with masses in the range 100 GeV < m((T) over tilde) < 410 GeV are excluded at 95% confidence level. If the decay is into a b-quark and a light quark, a dedicated selection requiring two b-tags is used to exclude masses in the ranges 100 GeV < m((t) over tilde) < 470 GeV and 480 GeV < m(<(t)over tilde>) < 610 GeV. Additional limits are set on the pair-production of massive colour-octet resonances.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-225873 (URN)10.1140/epjc/s10052-018-5693-4 (DOI)000428180600005 ()
Note

QC 20180411

Available from: 2018-04-11 Created: 2018-04-11 Last updated: 2018-06-04Bibliographically approved
Aaboud, M., Kastanas, K. A., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., . . . et al., . (2018). A search for resonances decaying into a Higgs boson and a new particle X in the XH -> qqbb final state with the ATLAS detector. Physics Letters B, 779, 24-45
Open this publication in new window or tab >>A search for resonances decaying into a Higgs boson and a new particle X in the XH -> qqbb final state with the ATLAS detector
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2018 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 779, p. 24-45Article in journal (Refereed) Published
Abstract [en]

A search for heavy resonances decaying into a Higgs boson (H) and a new particle (X) is reported, utilizing 36.1 fb(-1) of proton-proton collision data at root s = 13 TeV collected during 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. The particle Xis assumed to decay to a pair of light quarks, and the fully hadronic final state XH -> q (q) over bar 'b (b) over bar is analysed. The search considers the regime of high XH resonance masses, where the X and H bosons are both highly Lorentz-boosted and are each reconstructed using a single jet with large radius parameter. A two-dimensional phase space of XH mass versus X mass is scanned for evidence of a signal, over a range of XH resonance mass values between 1 TeV and 4 TeV, and for X particles with masses from 50 GeV to 1000 GeV. All search results are consistent with the expectations for the background due to Standard Model processes, and 95% CL upper limits are set, as a function of XH and X masses, on the production cross-section of the XH -> q (q) over bar 'b (b) over bar resonance.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-228200 (URN)10.1016/j.physletb.2018.01.042 (DOI)000429098900004 ()2-s2.0-85046461175 (Scopus ID)
Note

QC 20180518

Available from: 2018-05-18 Created: 2018-05-18 Last updated: 2018-11-13Bibliographically approved
Aaboud, M., Kastanas, K. A., Lund-Jensen, B., Ohm, C., Sidebo, P. E., Strandberg, J., . . . et al., . (2018). Angular analysis of B-d(0) -> K* mu(+)mu(-) decays in pp collisions at root s=8 TeV with the ATLAS detector. Journal of High Energy Physics (JHEP) (10), Article ID 047.
Open this publication in new window or tab >>Angular analysis of B-d(0) -> K* mu(+)mu(-) decays in pp collisions at root s=8 TeV with the ATLAS detector
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2018 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 10, article id 047Article in journal (Refereed) Published
Abstract [en]

An angular analysis of the decay B-d(0) -> K*mu(+)mu(-) is presented, based on proton-proton collision data recorded by the ATLAS experiment at the LHC. The study is using 20.3 fb(-1) of integrated luminosity collected during 2012 at centre-of-mass energy of root s = 8TeV. Measurements of the K* longitudinal polarisation fraction and a set of angular parameters obtained for this decay are presented. The results are compatible with the Standard Model predictions.

Place, publisher, year, edition, pages
SPRINGER, 2018
Keywords
Hadron-Hadron scattering (experiments)
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-238127 (URN)10.1007/JHEP10(2018)047 (DOI)000447258900001 ()2-s2.0-85054661404 (Scopus ID)
Note

QC 20181030

Available from: 2018-10-30 Created: 2018-10-30 Last updated: 2018-10-30Bibliographically approved
Aaboud, M., Kastanas, K. A., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., . . . et al., . (2018). Combination of inclusive and differential t(t)over-bar charge asymmetry measurements using ATLAS and CMS data at root S =7 and 8 TeV. Journal of High Energy Physics (JHEP) (4), Article ID 033.
Open this publication in new window or tab >>Combination of inclusive and differential t(t)over-bar charge asymmetry measurements using ATLAS and CMS data at root S =7 and 8 TeV
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2018 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 4, article id 033Article in journal (Refereed) Published
Abstract [en]

This paper presents combinations of inclusive and differential measurements of the charge asymmetry (A(C)) in top quark pair (t(t)over-bar) events with a lepton+jets signature by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. The data correspond to integrated luminosities of about 5 and 20 fb(-1) for each experiment, respectively. The resulting combined LHC measurements of the inclusive charge asymmetry are A(C)(LHC7) = 0.005 +/- 0.007 (stat) +/- 0.006 (syst) at 7 TeV and A(C)(LHC8) = 0.0055 +/- 0.0023 (stat) +/- 0.0025 (syst) at 8 TeV. These values, as well as the combination of A(C )measurements as a function of the invariant mass of the t(t)over-bar system at 8 TeV, are consistent with the respective standard model predictions.

Place, publisher, year, edition, pages
Springer-Verlag New York, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-229060 (URN)10.1007/JEHPO4(2018)033 (DOI)000432038500001 ()2-s2.0-85048748130 (Scopus ID)
Note

QC 20180531

Available from: 2018-05-31 Created: 2018-05-31 Last updated: 2018-11-23Bibliographically approved
Aaboud, M., Kastanas, K. A., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., . . . et al., . (2018). Combination of searches for heavy resonances decaying into bosonic and leptonic final states using 36 fb(-1) of proton-proton collision data at root s=13 TeV with the ATLAS detector. Physical Review D. Particles and fields, 98(5), Article ID 052008.
Open this publication in new window or tab >>Combination of searches for heavy resonances decaying into bosonic and leptonic final states using 36 fb(-1) of proton-proton collision data at root s=13 TeV with the ATLAS detector
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2018 (English)In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 98, no 5, article id 052008Article in journal (Refereed) Published
Abstract [en]

Searches for new heavy resonances decaying into different pairings of W, Z, or Higgs bosons, as well as dirffiffiffiectly into leptons, are presented using a data sample corresponding to 36.1 fb(-1) of pp collisions at root s = 13 TeV collected during 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Analyses selecting bosonic decay modes in the qqqq, vvqq, evqq, eeqq, evev, eevv, evee, eeee, qqbb, vvbb, evbb, and eebb final states are combined, searching for a narrow-width resonance. Likewise, analyses selecting the leptonic ev and ee final states are also combined. These two sets of analyses are then further combined. No significant deviation from the Standard Model predictions is observed. Three benchmark models are tested: a model predicting the existence of a new heavy scalar singlet, a simplified model predicting a heavy vector-boson triplet, and a bulk Randall-Sundrum model with a heavy spin-2 Kaluza-Klein excitation of the graviton. Cross section limits are set at the 95% confidence level using an asymptotic approximation and are compared with predictions for the benchmark models. These limits are also expressed in terms of constraints on couplings of the heavy vector-boson triplet to quarks, leptons, and the Higgs boson. The data exclude a heavy vector-boson triplet with mass below 5.5 TeV in a weakly coupled scenario and 4.5 TeV in a strongly coupled scenario, as well as a Kaluza-Klein graviton with mass below 2.3 TeV.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-236067 (URN)10.1103/PhysRevD.98.052008 (DOI)000445727900001 ()
Funder
Wallenberg Foundations
Note

QC 20181015

Available from: 2018-10-15 Created: 2018-10-15 Last updated: 2018-10-15Bibliographically approved
Aaboud, M., Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J. & et. al, . (2018). Combination of the Searches for Pair-Produced Vectorlike Partners of the Third-Generation Quarks at root s=13 TeV with the ATLAS Detector. Physical Review Letters, 121(21), Article ID 211801.
Open this publication in new window or tab >>Combination of the Searches for Pair-Produced Vectorlike Partners of the Third-Generation Quarks at root s=13 TeV with the ATLAS Detector
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2018 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 121, no 21, article id 211801Article in journal (Refereed) Published
Abstract [en]

A combination of the searches for pair-produced vectorlike partners of the top and bottom quarks in various decay channels (T -> Zt/Wb/Ht, B -> Zb/Wt/Hb) is performed using 36.1 fb(-1) of pp collision data at root s = 13 TeV with the ATLAS detector at the Large Hadron Collider. The observed data are found to be in good agreement with the standard model background prediction in all individual searches. Therefore, combined 95% confidence-level upper limits are set on the production cross section for a range of vectorlike quark scenarios, significantly improving upon the reach of the individual searches. Model-independent limits are set assuming the vectorlike quarks decay to standard model particles. A singlet T is excluded for masses below 1.31 TeV and a singlet B is excluded for masses below 1.22 TeV. Assuming a weak isospin (T, B) doublet and vertical bar V-Tb vertical bar << vertical bar V-tB vertical bar, T and B masses below 1.37 TeV are excluded.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-239998 (URN)10.1103/PhysRevLett.121.211801 (DOI)000451008600002 ()30517796 (PubMedID)
Note

QC 20181210

Available from: 2018-12-10 Created: 2018-12-10 Last updated: 2018-12-10Bibliographically approved
Aaboud, M., Kastanas, K. A., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., . . . Zwalinski, L. (2018). Combined measurement of differential and total cross sections in the H → γγ and the H → ZZ⁎ → 4ℓ decay channels at s=13 TeV with the ATLAS detector. Physics Letters B, 786, 114-133
Open this publication in new window or tab >>Combined measurement of differential and total cross sections in the H → γγ and the H → ZZ⁎ → 4ℓ decay channels at s=13 TeV with the ATLAS detector
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2018 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 786, p. 114-133Article in journal (Refereed) Published
Abstract [en]

A combined measurement of differential and inclusive total cross sections of Higgs boson production is performed using 36.1 fb−1 of 13 TeV proton–proton collision data produced by the LHC and recorded by the ATLAS detector in 2015 and 2016. Cross sections are obtained from measured H→γγ and H→ZZ⁎→4ℓ event yields, which are combined taking into account detector efficiencies, resolution, acceptances and branching fractions. The total Higgs boson production cross section is measured to be 57.0−5.9 +6.0 (stat.) −3.3 +4.0 (syst.) pb, in agreement with the Standard Model prediction. Differential cross-section measurements are presented for the Higgs boson transverse momentum distribution, Higgs boson rapidity, number of jets produced together with the Higgs boson, and the transverse momentum of the leading jet. The results from the two decay channels are found to be compatible, and their combination agrees with the Standard Model predictions.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-239556 (URN)10.1016/j.physletb.2018.09.019 (DOI)000452318400016 ()2-s2.0-85054192203 (Scopus ID)
Note

QC 20181126

Available from: 2018-11-26 Created: 2018-11-26 Last updated: 2019-01-08Bibliographically approved
Aaboudd, M., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E. & Strandberg, J. (2018). Constraints on off-shell Higgs boson production and the Higgs boson total width in ZZ -> 4l and ZZ -> 2l2v final states with the ATLAS detector. Physics Letters B, 786, 223-244
Open this publication in new window or tab >>Constraints on off-shell Higgs boson production and the Higgs boson total width in ZZ -> 4l and ZZ -> 2l2v final states with the ATLAS detector
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2018 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 786, p. 223-244Article in journal (Refereed) Published
Abstract [en]

A measurement of off-shell Higgs boson production in the ZZ -> 4l and ZZ -> 2l2v decay channels, where stands for either an electron or a muon, is performed using data from proton-proton collisions at a centre-of-mass energy of root s = 13 TeV. The data were collected by the ATLAS experiment in 2015 and 2016 at the Large Hadron Collider, and they correspond to an integrated luminosity of 36.1 fb(-1). An observed (expected) upper limit on the off-shell Higgs signal strength, defined as the event yield normalised to the Standard Model prediction, of 3.8 (3.4) is obtained at 95% confidence level (CL). Assuming the ratio of the Higgs boson couplings to the Standard Model predictions is independent of the momentum transfer of the Higgs production mechanism considered in the analysis, a combination with the on-shell signal-strength measurements yields an observed (expected) 95% CL upper limit on the Higgs boson total width of 14.4 (15.2) MeV.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-241166 (URN)10.1016/j.physletb.2018.09.048 (DOI)000452318400028 ()2-s2.0-850544292492-s2.0-85054429249 (Scopus ID)
Note

QC 20190115

Available from: 2019-01-15 Created: 2019-01-15 Last updated: 2019-01-15Bibliographically approved
Aaboud, M., Kastanas, K. A., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., . . . et al., . (2018). Direct top-quark decay width measurement in the t(t)over-bar lepton+jetschannel at root s=8 TeV with the ATLAS experiment. European Physical Journal C, 78(2), Article ID 129.
Open this publication in new window or tab >>Direct top-quark decay width measurement in the t(t)over-bar lepton+jetschannel at root s=8 TeV with the ATLAS experiment
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2018 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 78, no 2, article id 129Article in journal (Refereed) Published
Abstract [en]

This paper presents a direct measurement of the decay width of the top quark using t (t) over bar events in the lepton+jets final state. The data sample was collected by the ATLAS detector at the LHC in proton-proton collisions at a centre-of-mass energy of 8 TeV and corresponds to an integrated luminosity of 20.2 fb(-1). The decay width of the top quark is measured using a template fit to distributions of kinematic observables associated with the hadronically and semileptonically decaying top quarks. The result, Gamma(t) = 1.76 +/- 0.33 (stat.) (+0.79)(-0.68) (syst.) GeV for a top-quark mass of 172.5 GeV, is consistent with the prediction of the Standard Model.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-224773 (URN)10.1140/epjc/s10052-018-5595-5 (DOI)000425393800001 ()2-s2.0-85042217176 (Scopus ID)
Note

QC 20180323

Available from: 2018-03-23 Created: 2018-03-23 Last updated: 2018-05-17Bibliographically approved
Aaboud, M., Kastanas, K. A., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., . . . et.al., . (2018). Evidence for the associated production of the Higgs boson and a top quark pair with the ATLAS detector. Physical Review C. Nuclear Physics
Open this publication in new window or tab >>Evidence for the associated production of the Higgs boson and a top quark pair with the ATLAS detector
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2018 (English)In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490XArticle in journal (Refereed) Published
Abstract [en]

A search for the associated production of the Higgs boson with a top quark pair ((tt) over barH) is reported. The search is performed in multilepton final states using a data set corresponding to an integrated luminosity of 36.1 fb(-1) of proton-proton collision data recorded by the ATLAS experiment at a center-of-mass energy root s = 13 TeV at the Large Hadron Collider. Higgs boson decays to WW*, tau tau, and ZZ* are targeted. Seven final states, categorized by the number and flavor of charged-lepton candidates, are examined for the presence of the Standard Model Higgs boson with a mass of 125 GeVand a pair of top quarks. An excess of events over the expected background from Standard Model processes is found with an observed significance of 4.1 standard deviations, compared to an expectation of 2.8 standard deviations. The best fit for the (tt) over barH production cross section is sot (tt) over barH) = 790(-210)(+230) fb, in agreement with the Standard Model prediction of 507(-50)(+35) fb. The combination of this result with other t <overline> tH searches from the ATLAS experiment using the Higgs boson decay modes to b (b) over bar, gamma gamma and ZZ* -> 4l, has an observed significance of 4.2 standard deviations, compared to an expectation of 3.8 standard deviations. This provides evidence for the (tt) over barH production mode.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-227854 (URN)10.1103/PhysRevD.97.072003 (DOI)000429456900001 ()2-s2.0-85046831163 (Scopus ID)
Note

QC 20180514

Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2018-11-13Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-8913-0981

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