(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Fiducial cross-sections for ... production with one or two additional b-jets are reported, using an integrated luminosity ...of 20.3 fb... of proton-proton collisions at a centre-of-mass energy of 8 TeV at the Large Hadron Collider, collected with the ATLAS detector. The cross-section times branching ratio for ... events with at least one additional b-jet is measured to be 950 ... 70 (stat.) ... (syst.) fb in the lepton-plus-jets channel and 50 ... 10 (stat.) ... (syst.) fb in the ... channel. The cross-section times branching ratio for events with at least two additional b-jets is measured to be 19.3 ... 3.5 (stat.) ... 5.7 (syst.) fb in the dilepton channel (..., ..., and ee) using a method based on tight selection criteria, and 13.5 ... 3.3 (stat.) ... 3.6 (syst.) fb using a looser selection that allows the background normalisation to be extracted from data. The latter method also measures a value of 1.30 ... 0.33 (stat.) ... 0.28 (syst.)% for the ratio of ... production with two additional b-jets to ... production with any two additional jets. All measurements are in good agreement with recent theory predictions.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The production of a Z boson in association with a J/psi meson in proton-proton collisions probes the production mechanisms of quarkonium and heavy flavour in association with vector bosons, and ...allows studies of multiple parton scattering. Using 20.3 fb^-1 of data collected with the ATLAS experiment at the LHC in pp collisions at (sqrt)s=8 TeV, the first measurement of associated Z + Jpsi production is presented for both prompt and non-prompt J/psi production, with both signatures having a significance in excess of 5(sigma). The inclusive production cross-sections for Z boson production (analysed in mu^+mu^- or e^+e^- decay modes) in association with prompt and non-prompt J/psi (rightarrow mu^+mu^-) are measured relative to the inclusive production rate of Z bosons in the same fiducial volume to be (36.8 +/- 6.7 +/- 2.5) x 10^-7 and (65.8 +/- 9.2 +/- 4.2) x 10^-7 respectively. Normalised differential production cross-section ratios are also determined as a function of the Jpsi transverse momentum. The fraction of signal events arising from single and double parton scattering is estimated, and a lower limit of 5.3 (3.7) mb at 68 (95)% confidence level is placed on the effective cross-section regulating double parton interactions.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) A search for a charged Higgs boson (H ^sup +^) in ... decays is presented, where one of the top quarks decays via tarrow ...rightH ^sup +^ b, followed by H ^sup +^arrow right two jets (...). The other top quark decays to Wb, where the W boson then decays into a lepton (e/mu) and a neutrino. The data were recorded in pp collisions at ... by the ATLAS detector at the LHC in 2011, and correspond to an integrated luminosity of 4.7 fb^sup -1^. With no observation of a signal, 95 % confidence level (CL) upper limits are set on the decay branching ratio of top quarks to charged Higgs bosons varying between 5 % and 1 % for H ^sup +^ masses between 90 GeV and 150 GeV, assuming ...
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A measurement of splitting scales, as defined by the k ^sub T^ clustering algorithm, is presented for final states containing a W boson produced in proton-proton collisions at a centre-of-mass energy ...of 7 TeV. The measurement is based on the full 2010 data sample corresponding to an integrated luminosity of 36 pb^sup -1^ which was collected using the ATLAS detector at the CERN Large Hadron Collider. Cluster splitting scales are measured in events containing W bosons decaying to electrons or muons. The measurement comprises the four hardest splitting scales in a k ^sub T^ cluster sequence of the hadronic activity accompanying the W boson, and ratios of these splitting scales. Backgrounds such as multi-jet and top-quark-pair production are subtracted and the results are corrected for detector effects. Predictions from various Monte Carlo event generators at particle level are compared to the data. Overall, reasonable agreement is found with all generators, but larger deviations between the predictions and the data are evident in the soft regions of the splitting scales.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A measurement of the top quark pair production cross section in the final state with a hadronically decaying tau lepton and jets is presented. The analysis is based on proton-proton collision data ...recorded by the ATLAS experiment at the LHC, with a centre-of-mass energy of 7 TeV. The data sample corresponds to an integrated luminosity of 1.67 fb.sup.-1. The cross section is measured to be σ.sub.tbar.t = 194 ± 18 (stat.) ± 46 (syst.) pb and is in agreement with other measurements and with the Standard Model prediction.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) This article presents searches for the Zγ decay of the Higgs boson and for narrow high-mass resonances decaying to Zγ, ...exploiting Z boson decays to pairs of electrons or muons. The data analysis uses 36.1 fb−1 of pp collisions at ... recorded by the ATLAS detector at the CERN Large Hadron Collider. The data are found to be consistent with the expected Standard Model background. The observed (expected — assuming Standard Model pp → H → Zγ production and decay) upper limit on the production cross section times the branching ratio for pp → H → Zγ is 6.6. (5.2) times the Standard Model prediction at the 95% confidence level for a Higgs boson mass of 125.09 GeV. In addition, upper limits are set on the production cross section times the branching ratio as a function of the mass of a narrow resonance between 250 GeV and 2.4 TeV, assuming spin-0 resonances produced via gluon-gluon fusion, and spin-2 resonances produced via gluon-gluon or quark-antiquark initial states. For high-mass spin-0 resonances, the observed (expected) limits vary between 88 fb (61 fb) and 2.8 fb (2.7 fb) for the mass range from 250 GeV to 2.4 TeV at the 95% confidence level. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) A search for strongly produced supersymmetric particles using signatures involving multiple energetic jets and either two ...isolated same-sign leptons (e or μ), or at least three isolated leptons, is presented. The analysis relies on the identification of b-jets and high missing transverse momentum to achieve good sensitivity. A data sample of proton-proton collisions at ... TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015 and 2016, corresponding to a total integrated luminosity of 36.1 fb−1, is used for the search. No significant excess over the Standard Model prediction is observed. The results are interpreted in several simplified supersymmetric models featuring R-parity conservation or R-parity violation, extending the exclusion limits from previous searches. In models considering gluino pair production, gluino masses are excluded up to 1.87 TeV at 95% confidence level. When bottom squarks are pair-produced and decay to a chargino and a top quark, models with bottom squark masses below 700 GeV and light neutralinos are excluded at 95% confidence level. In addition, model-independent limits are set on a possible contribution of new phenomena to the signal region yields. Figure not available: see fulltext.
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