Change search
Link to record
Permanent link

Direct link
Publications (10 of 355) Show all publications
Bertoli, G., Bessidskaia Bylund, O., Bohm, C., Carney, R. M. D., Clément, C., Gellerstedt, K., . . . Wallängen, V. (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.
Open this publication in new window or tab >>A strategy for a general search for new phenomena using data-derived signal regions and its application within the ATLAS experiment
Show others...
2019 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 79, no 2, article id 120Article in journal (Refereed) 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.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-166542 (URN)10.1140/epjc/s10052-019-6540-y (DOI)000457998500007 ()
Available from: 2019-03-06 Created: 2019-03-06 Last updated: 2022-03-23Bibliographically approved
Abulaiti, Y., Bertoli, G., Bessidskaia Bylund, O., Bohm, C., Carney, R. M. D., Clement, C., . . . Wallängen, V. (2019). Search for light resonances decaying to boosted quark pairs and produced in association with a photon or a jet in proton-proton collisions at root s=13 TeV with the ATLAS detector. Physics Letters B, 788, 316-335
Open this publication in new window or tab >>Search for light resonances decaying to boosted quark pairs and produced in association with a photon or a jet in proton-proton collisions at root s=13 TeV with the ATLAS detector
Show others...
2019 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 788, p. 316-335Article in journal (Refereed) Published
Abstract [en]

This Letter presents a search for new light resonances decaying to pairs of quarks and produced in association with a high-p(T) photon or jet. The dataset consists of proton-proton collisions with an integrated luminosity of 36.1 fb(-1) at a centre-of-mass energy of root s = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider. Resonance candidates are identified as massive large-radius jets with substructure consistent with a particle decaying into a quark pair. The mass spectrum of the candidates is examined for local excesses above background. No evidence of a new resonance is observed in the data, which are used to exclude the production of a lepto-phobic axial-vector Z' boson.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-165672 (URN)10.1016/j.physletb.2018.09.062 (DOI)000455364400042 ()
Available from: 2019-02-06 Created: 2019-02-06 Last updated: 2022-03-23Bibliographically approved
Abulaiti, Y., Åkerstedt, H., Bendtz, K., Bertoli, G., Bessidskaia Bylund, O., Bohm, C., . . . Wallängen, V. (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), Article ID 250.
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
Show others...
2018 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 78, no 3, article id 250Article 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.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-156093 (URN)10.1140/epjc/s10052-018-5693-4 (DOI)000428180600005 ()
Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2022-03-23Bibliographically approved
Abulaiti, Y., Åkerstedt, H., Bertoli, G., Bessidskaia Bylund, O., Bohm, C., Carney, R. M. D., . . . Wallängen, V. (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
Show others...
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.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-156739 (URN)10.1016/j.physletb.2018.01.042 (DOI)000429098900004 ()
Available from: 2018-06-18 Created: 2018-06-18 Last updated: 2022-03-23Bibliographically approved
Abulaiti, Y., Åkerstedt, H., Bendtz, K., Bertoli, G., Bessidskaia Bylund, O., Bohm, C., . . . Wallängen, V. (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
Show others...
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.

Keywords
Hadron-Hadron scattering (experiments)
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-161981 (URN)10.1007/JHEP10(2018)047 (DOI)000447258900001 ()
Available from: 2018-11-20 Created: 2018-11-20 Last updated: 2022-03-23Bibliographically approved
Abulaiti, Y., Bertoli, G., Bessidskaia Bylund, O., Bohm, C., Carney, R. M. D., Clément, C., . . . Wallängen, V. (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
Show others...
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.

Keywords
Hadron-Hadron scattering (experiments), Top physics
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-157818 (URN)10.1007/JHEP04(2018)033 (DOI)000432038500001 ()
Available from: 2018-06-26 Created: 2018-06-26 Last updated: 2022-03-23Bibliographically approved
Bertoli, G., Bessidskaia Bylund, O., Bohm, C., Carney, R. M. D., Clement, C., Gellerstedt, K., . . . Wallängen, V. (2018). Evidence for the associated production of the Higgs boson and a top quark pair with the ATLAS detector. Physical Review D: covering particles, fields, gravitation, and cosmology, 97(7), Article ID 072003.
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
Show others...
2018 (English)In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 97, no 7, article id 072003Article 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.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-155948 (URN)10.1103/PhysRevD.97.072003 (DOI)000429456900001 ()
Available from: 2018-05-22 Created: 2018-05-22 Last updated: 2022-03-23Bibliographically approved
Abulaiti, Y., Bertoli, G., Bessidskaia Bylund, O., Bohm, C., Carney, R. M. D., Gellerstedt, K., . . . Wallängen, V. (2018). Measurement of colour flow using jet-pull observables in in t(t)over-bar events with the ATLAS experiment at root s=13TeV. European Physical Journal C, 78(10), Article ID 847.
Open this publication in new window or tab >>Measurement of colour flow using jet-pull observables in in t(t)over-bar events with the ATLAS experiment at root s=13TeV
Show others...
2018 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 78, no 10, article id 847Article in journal (Refereed) Published
Abstract [en]

Previous studies have shown that weighted angular moments derived from jet constituents encode the colour connections between partons that seed the jets. This paper presents measurements of two such distributions, the jet-pull angle and jet-pull magnitude, both of which are derived from the jet-pull angular moment. The measurement is performed in delivered by the Large Hadron Collider. The observables are measured for two dijet systems, corresponding to the colour-connected daughters of the Wboson and the two b-jets from the top-quark decays, which are not expected to be colour connected. To allow the comparison of the measured distributions to colour model predictions, the measured distributions are unfolded to particle level, after correcting for experimental effects introduced by the detector. While good agreement can be found for some combinations of predictions and observables, none of the predictions describes the data well across all observables.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-161920 (URN)10.1140/epjc/s10052-018-6290-2 (DOI)000448080300001 ()
Available from: 2018-11-13 Created: 2018-11-13 Last updated: 2022-03-23Bibliographically approved
Abulaiti, Y., Åkerstedt, H., Bertoli, G., Bessidskaia Bylund, O., Bohm, C., Carney, R. M. D., . . . Wallängen, V. (2018). Measurement of differential cross sections and W+/W- cross-section ratios for W boson production in association with jets at root s=8 TeV with the ATLAS detector. Journal of High Energy Physics (JHEP) (5), Article ID 077.
Open this publication in new window or tab >>Measurement of differential cross sections and W+/W- cross-section ratios for W boson production in association with jets at root s=8 TeV with the ATLAS detector
Show others...
2018 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 5, article id 077Article in journal (Refereed) Published
Abstract [en]

This paper presents a measurement of the W boson production cross section and the W+/W- cross-section ratio, both in association with jets, in proton-proton collisions at root s = 8 TeV with the ATLAS experiment at the Large Hadron Collider. The measurement is performed in final states containing one electron and missing transverse momentum using data corresponding to an integrated luminosity of 20.2 fb(-1). Differential cross sections for events with at least one or two jets are presented for a range of observables, including jet transverse momenta and rapidities, the scalar sum of transverse momenta of the visible particles and the missing transverse momentum in the event, and the transverse momentum of the W boson. For a subset of the observables, the differential cross sections of positively and negatively charged W bosons are measured separately. In the cross-section ratio of W+/W- the dominant systematic uncertainties cancel out, improving the measurement precision by up to a factor of nine. The observables and ratios selected for this paper provide valuable input for the up quark, down quark, and gluon parton distribution functions of the proton.

Keywords
Hadron-Hadron scattering (experiments)
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-157774 (URN)10.1007/JHEP05(2018)077 (DOI)000432561800001 ()
Available from: 2018-06-25 Created: 2018-06-25 Last updated: 2022-03-23Bibliographically approved
Abulaiti, Y., Åkerstedt, H., Bertoli, G., Bessidskaia Bylund, O., Bohm, C., Carney, R. M. D., . . . Wallängen, V. (2018). Measurement of differential cross sections of isolated-photon plus heavy-flavour jet production in pp collisions at root s=8 TeV using the ATLAS detector. Physics Letters B, 776, 295-317
Open this publication in new window or tab >>Measurement of differential cross sections of isolated-photon plus heavy-flavour jet production in pp collisions at root s=8 TeV using the ATLAS detector
Show others...
2018 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 776, p. 295-317Article in journal (Refereed) Published
Abstract [en]

This Letter presents the measurement of differential cross sections of isolated prompt photons produced in association with a b-jet or a c-jet. These final states provide sensitivity to the heavy-flavour content of the proton and aspects related to the modelling of heavy-flavour quarks in perturbative QCD. The measurement uses proton-proton collision data at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of up to 20.2 fb(-1). The differential cross sections are measured for each jet flavour with respect to the transverse energy of the leading photon in two photon pseudorapidity regions: vertical bar eta(gamma)vertical bar < 1.37 and 1.56 < vertical bar eta(gamma)vertical bar < 2.37. The measurement covers photon transverse energies 25 < E-T(gamma) < 400 GeV and 25 < E-T(gamma) < 350 GeV respectively for the two vertical bar eta(gamma)vertical bar regions. For each jet flavour, the ratio of the cross sections in the two vertical bar eta(gamma)vertical bar regions is also measured. The measurement is corrected for detector effects and compared to leading-order and next-to-leading-order perturbative QCD calculations, based on various treatments and assumptions about the heavy-flavour content of the proton. Overall, the predictions agree well with the measurement, but some deviations are observed at high photon transverse energies. The total uncertainty in the measurement ranges between 13% and 66%, while the central gamma+b measurement exhibits the smallest uncertainty, ranging from 13% to 27%, which is comparable to the precision of the theoretical predictions.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-153827 (URN)10.1016/j.physletb.2017.11.054 (DOI)000419641100043 ()
Available from: 2018-03-09 Created: 2018-03-09 Last updated: 2022-03-23Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5690-0521

Search in DiVA

Show all publications