The dijet production cross section for jets containing a
-hadron (
-jets) has been measured in proton-proton collisions with a centre-of-mass energy of Formula: see text TeV, using the ATLAS detector ...at the LHC. The data used correspond to an integrated luminosity of Formula: see text. The cross section is measured for events with two identified
-jets with a transverse momentum Formula: see text GeV and a minimum separation in the Formula: see text-Formula: see text plane of Formula: see text. At least one of the jets in the event is required to have Formula: see text GeV. The cross section is measured differentially as a function of dijet invariant mass, dijet transverse momentum, boost of the dijet system, and the rapidity difference, azimuthal angle and angular distance between the
-jets. The results are compared to different predictions of leading order and next-to-leading order perturbative quantum chromodynamics matrix elements supplemented with models for parton-showers and hadronization.
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The decays Formula: see text and Formula: see text are studied with the ATLAS detector at the LHC using a dataset corresponding to integrated luminosities of 4.9 and 20.6 fbFormula: see text of
...collisions collected at centre-of-mass energies Formula: see text TeV and 8 TeV, respectively. Signal candidates are identified through Formula: see text and Formula: see text decays. With a two-dimensional likelihood fit involving the Formula: see text reconstructed invariant mass and an angle between the Formula: see text and Formula: see text candidate momenta in the muon pair rest frame, the yields of Formula: see text and Formula: see text, and the transverse polarisation fraction in Formula: see text decay are measured. The transverse polarisation fraction is determined to be Formula: see text, and the derived ratio of the branching fractions of the two modes is Formula: see text, where the first error is statistical and the second is systematic. Finally, a sample of Formula: see text decays is used to derive the ratios of branching fractions Formula: see text and Formula: see text, where the third error corresponds to the uncertainty of the branching fraction of Formula: see text decay. The available theoretical predictions are generally consistent with the measurement.
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The luminosity determination for the ATLAS detector at the LHC during
collisions at Formula: see text 8 TeV in 2012 is presented. The evaluation of the luminosity scale is performed using several ...luminometers, and comparisons between these luminosity detectors are made to assess the accuracy, consistency and long-term stability of the results. A luminosity uncertainty of Formula: see text is obtained for the Formula: see text of
collision data delivered to ATLAS at Formula: see text 8 TeV in 2012.
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Fiducial cross-sections for Formula: see text production with one or two additional
-jets are reported, using an integrated luminosity of 20.3 fbFormula: see text 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 Formula: see text events with at least one additional
-jet is measured to be 950 Formula: see text 70 (stat.) Formula: see text (syst.) fb in the lepton-plus-jets channel and 50 Formula: see text 10 (stat.) Formula: see text (syst.) fb in the Formula: see text channel. The cross-section times branching ratio for events with at least two additional
-jets is measured to be 19.3 Formula: see text 3.5 (stat.) Formula: see text 5.7 (syst.) fb in the dilepton channel (Formula: see text, Formula: see text, and
) using a method based on tight selection criteria, and 13.5 Formula: see text 3.3 (stat.) Formula: see text 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 Formula: see text 0.33 (stat.) Formula: see text 0.28 (syst.)% for the ratio of Formula: see text production with two additional
-jets to Formula: see text production with any two additional jets. All measurements are in good agreement with recent theory predictions.
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The results of a search for gluinos in final states with an isolated electron or muon, multiple jets and large missing transverse momentum using proton-proton collision data at a centre-of-mass ...energy of Formula: see text are presented. The dataset used was recorded in 2015 by the ATLAS experiment at the Large Hadron Collider and corresponds to an integrated luminosity of 3.2 fbFormula: see text. Six signal selections are defined that best exploit the signal characteristics. The data agree with the Standard Model background expectation in all six signal selections, and the largest deviation is a 2.1 standard deviation excess. The results are interpreted in a simplified model where pair-produced gluinos decay via the lightest chargino to the lightest neutralino. In this model, gluinos are excluded up to masses of approximately 1.6 Te V depending on the mass spectrum of the simplified model, thus surpassing the limits of previous searches.
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The paper presents studies of Bose-Einstein Correlations (BEC) for pairs of like-sign charged particles measured in the kinematic range Formula: see text 100 MeV and Formula: see text 2.5 in proton ...collisions at centre-of-mass energies of 0.9 and 7 TeV with the ATLAS detector at the CERN Large Hadron Collider. The integrated luminosities are approximately 7 Formula: see textbFormula: see text, 190 Formula: see textbFormula: see text and 12.4 nbFormula: see text for 0.9 TeV, 7 TeV minimum-bias and 7 TeV high-multiplicity data samples, respectively. The multiplicity dependence of the BEC parameters characterizing the correlation strength and the correlation source size are investigated for charged-particle multiplicities of up to 240. A saturation effect in the multiplicity dependence of the correlation source size parameter is observed using the high-multiplicity 7 TeV data sample. The dependence of the BEC parameters on the average transverse momentum of the particle pair is also investigated.
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Many extensions of the Standard Model predict the existence of charged heavy long-lived particles, such as
-hadrons or charginos. These particles, if produced at the Large Hadron Collider, should be ...moving non-relativistically and are therefore identifiable through the measurement of an anomalously large specific energy loss in the ATLAS pixel detector. Measuring heavy long-lived particles through their track parameters in the vicinity of the interaction vertex provides sensitivity to metastable particles with lifetimes from 0.6 ns to 30 ns. A search for such particles with the ATLAS detector at the Large Hadron Collider is presented, based on a data sample corresponding to an integrated luminosity of Formula: see text fbFormula: see text of
collisions at Formula: see text TeV. No significant deviation from the Standard Model background expectation is observed, and lifetime-dependent upper limits on
-hadrons and chargino production are set. Gluino
-hadrons with 10 ns lifetime and masses up to 1185 GeV are excluded at 95 Formula: see text confidence level, and so are charginos with 15 ns lifetime and masses up to 482 GeV.
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A search for Higgs boson pair production Formula: see text is performed with 19.5 fbFormula: see text of proton-proton collision data at Formula: see text TeV, which were recorded by the ATLAS ...detector at the Large Hadron Collider in 2012. The decay products of each Higgs boson are reconstructed as a high-momentum Formula: see text system with either a pair of small-radius jets or a single large-radius jet, the latter exploiting jet substructure techniques and associated
-tagged track-jets. No evidence for resonant or non-resonant Higgs boson pair production is observed. The data are interpreted in the context of the Randall-Sundrum model with a warped extra dimension as well as the two-Higgs-doublet model. An upper limit on the cross-section for Formula: see text of 3.2 (2.3) fb is set for a Kaluza-Klein graviton Formula: see text mass of 1.0 (1.5) TeV, at the 95 % confidence level. The search for non-resonant Standard Model
production sets an observed 95 % confidence level upper limit on the production cross-section Formula: see text of 202 fb, compared to a Standard Model prediction of Formula: see text fb.
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