| 1. |
- Abulaiti, Yiming, et al.
(author)
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Measurement of WW/WZ -> lvqq ' production with the hadronically decaying boson reconstructed as one or two jets in pp collisions at root s=8 TeV with ATLAS, and constraints on anomalous gauge couplings
- 2017
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In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 77:8
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Journal article (peer-reviewed)abstract
- This paper presents a study of the production of WW or WZ boson pairs, with one W boson decaying to ev or mu v and one W or Z boson decaying hadronically. The analysis uses 20.2 fb(-1) of root s = 8 TeV pp collision data, collected by the ATLAS detector at the Large Hadron Collider. Crosssections for WW/WZ production are measured in high-p(T) fiducial regions defined close to the experimental event selection. The cross-section is measured for the case where the hadronically decaying boson is reconstructed as two resolved jets, and the case where it is reconstructed as a single jet. The transverse momentum distribution of the hadronically decaying boson is used to search for new physics. Observations are consistent with the Standard Model predictions, and 95% confidence intervals are calculated for parameters describing anomalous triple gauge-boson couplings.
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| 2. |
- Abulaiti, Yiming, et al.
(author)
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Search for a scalar partner of the top quark in the jets plus missing transverse momentum final state at root s=13 TeV with the ATLAS detector
- 2017
-
In: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :12
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Journal article (peer-reviewed)abstract
- A search for pair production of a scalar partner of the top quark in events with four or more jets plus missing transverse momentum is presented. An analysis of 36.1 fb(-1) of root s = 13 TeV proton-proton collisions collected using the ATLAS detector at the LHC yields no significant excess over the expected Standard Model background. To interpret the results a simplified supersymmetric model is used where the top squark is assumed to decay via (t) over tilde (1) -> t((*)) (chi) over tilde (0)(1) and (t) over tilde (1) -> b (chi) over tilde (+/-)(1) -> bW((*)) (chi) over tilde (0)(1), where (chi) over tilde (0)(1) ((chi) over tilde (+/-)(1) denotes the lightest neutralino (chargino). Exclusion limits are placed in terms of the top-squark and neutralino masses. Assuming a branching ratio of 100% to t (chi) over tilde (0)(1), top-squark masses in the range 450-1000 GeV are excluded for (chi) over tilde (0)(1) masses below 160 GeV. In the case where m((t) over tilde1) similar to m(t) + m((chi) over tilde 10), top-squark masses in the range 235-590 GeV are excluded.
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| 3. |
- Abulaiti, Yiming, et al.
(author)
-
Search for new phenomena in a lepton plus high jet multiplicity final state the ATLAS experiment using root S=13 TeV proton-proton collision data
- 2017
-
In: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :9
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Journal article (peer-reviewed)abstract
- A search for new phenomena in final states characterized by high jet multiplicity, an isolated lepton ( electron or muon) and either zero or at least three b-tagged jets is presented. The search uses 36.1 fb(-1) of root s = 13TeV proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider in 2015 and 2016. The dominant sources of background are estimated using parameterized extrapolations, based on observables at medium jet multiplicity, to predict the b-tagged jet multiplicity distribution at the higher jet multiplicities used in the search. No significant excess over the Standard Model expectation is observed and 95% confidence-level limits are extracted constraining four simplified models of R-parity-violating supersymmetry that feature either gluino or top-squark pair production. The exclusion limits reach as high as 2.1TeV in gluino mass and 1.2TeV in top-squark mass in the models considered. In addition, an upper limit is set on the cross-section for Standard Model t (t) over bart (t) over bar production of 60 fb (6.5 x the Standard Model prediction) at 95% confidence level. Finally, model-independent limits are set on the contribution from new phenomena to the signal-region yields.
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| 4. |
- Abulaiti, Yiming, et al.
(author)
-
Search for new phenomena with large jet multiplicities and missing transverse momentum using large-radius jets and flavour-tagging at ATLAS in 13 TeV pp collisions
- 2017
-
In: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :12
-
Journal article (peer-reviewed)abstract
- A search is presented for particles that decay producing a large jet multiplicity and invisible particles. The event selection applies a veto on the presence of isolated electrons or muons and additional requirements on the number of b-tagged jets and the scalar sum of masses of large-radius jets. Having explored the full ATLAS 2015-2016 dataset of LHC proton-proton collisions at root s = 13 TeV, which corresponds to 36.1 fb(-1) of integrated luminosity, no evidence is found for physics beyond the Standard Model. The results are interpreted in the context of simplified models inspired by R-parity-conserving and R-parity-violating supersymmetry, where gluinos are pair-produced. More generic models within the phenomenological minimal supersymmetric Standard Model are also considered.
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| 5. |
- Milstead, David A., et al.
(author)
-
Search for the Dimuon Decay of the Higgs Boson in pp Collisions at s =13 TeV with the ATLAS Detector
- 2017
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In: Physical Review Letters. - : American Physical Society. - 1079-7114 .- 0031-9007. ; 119:5
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Journal article (peer-reviewed)abstract
- A search for the dimuon decay of the Higgs boson was performed using data corresponding to an integrated luminosity of 36.1 fb-1 collected with the ATLAS detector in pp collisions at s=13 TeV at the Large Hadron Collider. No significant excess is observed above the expected background. The observed (expected) upper limit on the cross section times branching ratio is 3.0 (3.1) times the Standard Model prediction at the 95% confidence level for a Higgs boson mass of 125 GeV. When combined with the pp collision data at s=7 TeV and s=8 TeV, the observed (expected) upper limit is 2.8 (2.9) times the Standard Model prediction. © 2017 CERN.
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| 6. |
- Aaboud, M, et al.
(author)
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Search for a Structure in the Bs0 π± Invariant Mass Spectrum with the ATLAS Experiment
- 2018
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In: Physical Review Letters. - : AMER PHYSICAL SOC. - 1079-7114 .- 0031-9007. ; 120:20
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Journal article (peer-reviewed)abstract
- A search for the narrow structure, X(5568), reported by the D0 Collaboration in the decay sequence X→Bs0π±, Bs0→J/ψφ, is presented. The analysis is based on a data sample recorded with the ATLAS detector at the LHC corresponding to 4.9 fb-1 of pp collisions at 7 TeV and 19.5 fb-1 at 8 TeV. No significant signal was found. Upper limits on the number of signal events, with properties corresponding to those reported by D0, and on the X production rate relative to Bs0 mesons, ρX, were determined at 95% confidence level. The results are N(X)
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| 7. |
- Abulaiti, Yiming, et al.
(author)
-
A search for pair-produced resonances in four-jet final states at root s=13 TeV with the ATLAS detector
- 2018
-
In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 78:3
-
Journal article (peer-reviewed)abstract
- 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.
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| 8. |
- Abulaiti, Yiming, et al.
(author)
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Angular analysis of B-d(0) -> K* mu(+)mu(-) decays in pp collisions at root s=8 TeV with the ATLAS detector
- 2018
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In: Journal of High Energy Physics (JHEP). - : SPRINGER. - 1126-6708 .- 1029-8479. ; :10
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Journal article (peer-reviewed)abstract
- 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.
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| 9. |
- Abulaiti, Yiming, et al.
(author)
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Identification and rejection of pile-up jets at high pseudorapidity with the ATLAS detector
- 2017
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In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 77:9
-
Journal article (peer-reviewed)abstract
- The rejection of forward jets originating from additional proton-proton interactions (pile-up) is crucial for a variety of physics analyses at the LHC, including Standard Model measurements and searches for physics beyond the Standard Model. The identification of such jets is challenging due to the lack of track and vertex information in the pseudorapidity range vertical bar eta vertical bar > 2.5. This paper presents a novel strategy for forward pile-up jet tagging that exploits jet shapes and topological jet correlations in pile-up interactions. Measurements of the per-jet tagging efficiency are presented using a data set of 3.2 fb(-1) of proton-proton collisions at a centre-of-mass energy of 13 TeV collected with the ATLAS detector. The fraction of pile-up jets rejected in the range 2.5 < vertical bar eta vertical bar < 4.5 is estimated in simulated events with an average of 22 interactions per bunch-crossing. It increases with jet transverse momentum and, for jets with transverse momentum between 20 and 50 GeV, it ranges between 49% and 67% with an efficiency of 85% for selecting hard-scatter jets. A case study is performed in Higgs boson production via the vector-boson fusion process, showing that these techniques mitigate the background growth due to additional proton-proton interactions, thus enhancing the reach for such signatures.
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| 10. |
- Abulaiti, Yiming, et al.
(author)
-
Measurement of b-hadron pair production with the ATLAS detector in proton-proton collisions at root s=8 TeV
- 2017
-
In: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :11
-
Journal article (peer-reviewed)abstract
- A measurement of b-hadron pair production is presented, based on a data set corresponding to an integrated luminosity of 11.4 fb(-1) of proton-proton collisions recorded at root s = 8TeV with the ATLAS detector at the LHC. Events are selected in which a b-hadron is reconstructed in a decay channel containing J = psi -> mu mu, and a second b-hadron is reconstructed in a decay channel containing a muon. Results are presented in a fiducial volume de fined by kinematic requirements on three muons based on those used in the analysis. The fiducial cross section is measured to be 17.7 +/- 0.1(stat.) +/- 2.0(syst.) nb. A number of normalised differential cross sections are also measured, and compared to predictions from the PYTHIA8, HERWIG++, MADGRAPH5_AMC@NLO+PYTHIA8 and SHERPA event generators, providing new constraints on heavy flavour production.
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