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At least 343 records · Page 19

Measurement of forward-backward multiplicity correlations in lead-lead, proton-lead, and proton-proton collisions with the ATLAS detector

Two-particle pseudorapidity correlations are measured in √ s NN = 2.76TeV Pb + Pb, √ s NN = 5.02TeV p + Pb, and √s = 13 TeV pp collisions at the Large Hadron Collider (LHC), with total integrated luminosities of approximately 7μb –1 , 28 nb –1 , and 65 nb –1 , respectively. The correlation function C N (η 1 ,η 2 ) is measured as a function of event multiplicity using charged particles in the pseudorapidity range |η| < 2.4. The correlation function contains a significant short-range component, which is estimated and subtracted. After removal of the short-range component, the shape of the correlation function is described approximately by 1 + < a2 1 > 1/2 η 1 η 2 in all collision systems over the full multiplicity range. The values of < a 2 1 > 1/2 are consistent for the opposite-charge pairs and same-charge pairs, and for the three collision systems at similar multiplicity. The values of < a 2 1 > 1/2 and the magnitude of the short-range component both follow a power-law dependence on the event multiplicity. Here, the short-range component in p + Pb collisions, after symmetrizing the proton and lead directions, is found to be smaller at a given η than in pp collisions with comparable multiplicity.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Search for the standard model Higgs boson produced in association with a vector boson and decaying into a tau pair in p p collisions at s = 8 TeV with the ATLAS detector

A search for the standard model Higgs boson produced in association with a vector boson with the decay H → τ τ is presented. The data correspond to 20.3 fb -1 of integrated luminosity from proton-proton collisions at √ s = 8 TeV recorded by the ATLAS experiment at the LHC during 2012.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Measurement of exclusive γ γ → W + W - production and search for exclusive Higgs boson production in p p collisions at s = 8 TeV using the ATLAS detector

Searches for exclusively produced W boson pairs in the process p p ( γ γ ) → p W + W - p and an exclusively produced Higgs boson in the process p p ( g g ) → p H p have been performed using e ± μ ∓ final states. These measurements use 20.2 fb - 1 of p p collisions collected by the ATLAS experiment at a center-of-mass energy √ s = 8 TeV at the LHC. Exclusive production of W + W - consistent with the Standard Model prediction is found with 3.0 σ significance. The exclusive W + W - production cross section is determined to be σ ( γ γ → W + W - → e ± μ ∓ X ) = 6.9 ± 2.2 ( stat ) ± 1.4 ( sys ) fb , in agreement with the Standard Model prediction. Limits on anomalous quartic gauge couplings are set at 95% confidence level as - 1.7 × 10 - 6 < a W 0 / Λ 2 < 1.7 × 10 - 6 GeV - 2 and - 6.4 × 10 - 6 < a W C / Λ 2 < 6.3 × 10 - 6 GeV - 2 . A 95% confidence-level upper limit on the total production cross section for an exclusive Higgs boson is set to 1.2 pb.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Search for anomalous electroweak production of W W / W Z in association with a high-mass dijet system in p p collisions at s = 8 TeV with the ATLAS detector

A search is presented for anomalous quartic gauge boson couplings in vector-boson scattering. Here, the data for the analysis correspond to 20.2 fb -1 of √ s = 8 TeV pp collisions and were collected in 2012 by the ATLAS experiment at the Large Hadron Collider. The search looks for the production of WW or WZ boson pairs accompanied by a high-mass dijet system, with one W decaying leptonically and a W or Z decaying hadronically. The hadronically decaying W/Z is reconstructed as either two small-radius jets or one large-radius jet using jet substructure techniques. Constraints on the anomalous quartic gauge boson coupling parameters α 4 and α 5 are set by fitting the transverse mass of the diboson system, and the resulting 95% confidence intervals are - 0.024 < α 4 < 0.030 and - 0.028 < α 5 < 0.033 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗