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Agustoni, M.

Publications and source records attributed to Agustoni, M..

At least 55 records · Page 3
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DOE OSTI2015

Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at $\sqrt{s}=8 $ TeV with the ATLAS detector

The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. The search is based on proton-proton collision data at a centre-of-mass energy √ = 8 TeV collected in 2012, corresponding to an integrated luminosity of 20 fb -1 . No significant excess above the Standard Model expectation is observed. Limits are set on supersymmetric particle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV. Limits are also set on the parameters of a minimal universal extra dimension model, excluding a compactification radius of 1/R c = 950 GeV for a cut-off scale times radius (ΛR c ) of approximately 30.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of Spin Correlation in Top-Antitop Quark Events and Search for Top Squark Pair Production in p p Collisions at s = 8 TeV Using the ATLAS Detector

A measurement of spin correlation in tt¯ production is presented using data collected with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb⁻¹. The correlation between the top and antitop quark spins is extracted from dilepton tt¯ events by using the difference in the azimuthal angle between the two charged leptons in the laboratory frame. In the helicity basis the measured degree of correlation corresponds to A helicity =0.38±0.04, in agreement with the standard model prediction. A search is performed for pair production of top squarks with masses close to the top quark mass decaying to predominantly right-handed top quarks and a light neutralino, the lightest supersymmetric particle. Top squarks with masses between the top quark mass and 191 GeV are excluded at the 95% confidence level.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Search for charged Higgs bosons decaying via H ± → τ ± ν in fully hadronic final states using pp collision data at s $$ \sqrt{s} $$ = 8 TeV with the ATLAS detector

The results of a search for charged Higgs bosons decaying to a τ lepton and a neutrino, H ± → τ ± ν, are presented. The analysis is based on 19.5 fb –1 of proton-proton collision data at √s = 8 TeV collected by the ATLAS experiment at the Large Hadron Collider. Charged Higgs bosons are searched for in events consistent with top-quark pair production or in associated production with a top quark, depending on the considered H ± mass. The final state is characterized by the presence of a hadronic τ decay, missing transverse momentum, b-tagged jets, a hadronically decaying W boson, and the absence of any isolated electrons or muons with high transverse momenta. The data are consistent with the expected background from Standard Model processes. A statistical analysis leads to 95% confidence-level upper limits on the product of branching ratios Β(t → bH ± ) × Β(H ± → τ ± ν), between 0.23% and 1.3% for charged Higgs boson masses in the range 80-160GeV. It also leads to 95% confidence-level upper limits on the production cross section times branching ratio, σ(pp → tH ± + X) × Β(H ± → τ ± ν), between 0.76 pb and 4.5 fb, for charged Higgs boson masses ranging from 180 GeV to 1000 GeV. In the context of different scenarios of the Minimal Supersymmetric Standard Model, these results exclude nearly all values of tan β above one for charged Higgs boson masses between 80 GeV and 160 GeV, and exclude a region of parameter space with high tan β for H ± masses between 200 GeV and 250 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Search for anomalous production of prompt same-sign lepton pairs and pair-produced doubly charged Higgs bosons with $ \sqrt{s}=8 $ TeV pp collisions using the ATLAS detector

A low-background inclusive search for new physics in events with same-sign dileptons is presented. The search uses proton-proton collisions corresponding to 20.3 fb -1 of integrated luminosity taken in 2012 at a centre-of-mass energy of 8 TeV with the ATLAS detector at the LHC. Pairs of isolated leptons with the same electric charge and large transverse momenta of the type e ± e ± , e ± μ ± , and μ ± μ ± are selected and their invariant mass distribution is examined. No excess of events above the expected level of Standard Model background is found. The results are used to set upper limits on the cross-sections for processes beyond the Standard Model. Limits are placed as a function of the dilepton invariant mass within a fiducial region corresponding to the signal event selection criteria. Exclusion limits are also derived for a specific model of doubly charged Higgs boson production.[Figure not available: see fulltext.]

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Simultaneous measurements of the t t ¯ , W + W – , and Z / γ * → τ τ production cross-sections in p p collisions at s = 7 TeV with the ATLAS detector

Simultaneous measurements of the tt¯, W⁺W⁻, and Z/γ ∗ → ττ production cross-sections using an integrated luminosity of 4.6 fb⁻¹ of pp collisions at √s = 7 TeV collected by the ATLAS detector at the LHC are presented. Events are selected with two high transverse momentum leptons consisting of an oppositely charged electron and muon pair. The three processes are separated using the distributions of the missing transverse momentum of events with zero and greater than zero jet multiplicities. Measurements of the fiducial cross-section are presented along with results that quantify for the first time the underlying correlations in the predicted and measured cross-sections due to proton parton distribution functions. These results indicate that the correlated next-to-leading-order predictions for tt¯ and Z/γ ∗ → ττ underestimate the data, while those at next-to-next-to-leading-order generally describe the data well. The full cross-sections are measured to be σ(tt¯) = 181.2 ± 2.8⁺⁹̣˙⁷₋₉̣₅ ± 3.3 ± 3.3 pb, σ(W⁺W⁻) = 53.3 ± 2.7⁺⁷˙³₋₈̣₀ ± 1.0 ± 0.5 pb, and σ(Z/γ ∗ → ττ) = 1174 ± 24⁺⁷²₋₈₇ ± 21 ± 9 pb, where the cited uncertainties are due to statistics, systematic effects, luminosity and the LHC beam energy measurement, respectively. The W⁺W⁻ measurement includes the small contribution from Higgs boson decays, H → W⁺W⁻.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Search for Higgs Boson pair production in the γ γ b b ¯ final state using p p collision data at s = 8 TeV from the ATLAS Detector

Searches are performed for resonant and nonresonant Higgs boson pair production in the γγbb¯ final state using 20 fb⁻¹ of proton-proton collisions at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the CERN Large Hadron Collider. A 95% confidence level upper limit on the cross section times branching ratio of nonresonant production is set at 2.2 pb, while the expected limit is 1.0 pb. The difference derives from a modest excess of events, corresponding to 2.4 standard deviations from the background-only hypothesis. The limit observed in the search for a narrow X → hh resonance ranges between 0.7 and 3.5 pb as a function of the resonance mass.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of the inclusive jet cross-section in proton-proton collisions at $ \sqrt{s}=7 $ TeV using 4.5 fb -1 of data with the ATLAS detector

The inclusive jet cross-section is measured in proton-proton collisions at a centre-of-mass energy of 7 TeV using a data set corresponding to an integrated luminosity of 4.5 fb -1 collected with the ATLAS detector at the Large Hadron Collider in 2011. Jets are identified using the anti-k t algorithm with radius parameter values of 0.4 and 0.6. The double-differential cross-sections are presented as a function of the jet transverse momentum and the jet rapidity, covering jet transverse momenta from 100 GeV to 2 TeV. Next-to-leading-order QCD calculations corrected for non-perturbative effects and electroweak effects, as well as Monte Carlo simulations with next-to-leading-order matrix elements interfaced to parton showering, are compared to the measured cross-sections. A quantitative comparison of the measured cross-sections to the QCD calculations using several sets of parton distribution functions is performed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Search for resonant diboson production in the $\mathrm {\ell \ell }q\bar{q}$ final state in $pp$ collisions at $\sqrt{s} = 8$ TeV with the ATLAS detector

This study reports on a search for narrow resonances in diboson production in the ℓℓqq¯ final state using pp collision data corresponding to an integrated luminosity of 20 fb –1 collected at √s=8 TeV with the ATLAS detector at the Large Hadron Collider. No significant excess of data events over the Standard Model expectation is observed. Upper limits at the 95 % confidence level are set on the production cross section times branching ratio for Kaluza–Klein gravitons predicted by the Randall–Sundrum model and for Extended Gauge Model W' bosons. These results lead to the exclusion of mass values below 740 and 1590 GeV for the graviton and W' boson respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Search for new phenomena in events with a photon and missing transverse momentum in p p collisions at s = 8 TeV with the ATLAS detector

Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum with the ATLAS experiment at the LHC are reported. Data were collected in proton-proton collisions at a center-of-mass energy of 8 TeV and correspond to an integrated luminosity of 20.3 fb⁻¹. The observed data are well described by the expected Standard Model backgrounds. The expected (observed) upper limit on the fiducial cross section for the production of events with a photon and large missing transverse momentum is 6.1 (5.3) fb at 95% confidence level. Exclusion limits are presented on models of new phenomena with large extra spatial dimensions, supersymmetric quarks, and direct pair production of dark-matter candidates.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Search for the $ b\overline{b} $ decay of the Standard Model Higgs boson in associated ( W/Z ) H production with the ATLAS detector

A search for the $ b\overline{b} $ decay of the Standard Model Higgs boson is performed with the ATLAS experiment using the full dataset recorded at the LHC in Run 1. The integrated luminosities used are 4.7 and 20.3 fb -1 from pp collisions at √s = 7 and 8 TeV, respectively. The processes considered are associated (W/Z)H production, where W → eν/μν, Z → ee/μμ and Z → νν. The observed (expected) deviation from the background-only hypothesis corresponds to a significance of 1.4 (2.6) standard deviations and the ratio of the measured signal yield to the Standard Model expectation is found to be μ = 0.52 ± 0.32 (stat.) ± 0.24 (syst.) for a Higgs boson mass of 125.36 GeV. The analysis procedure is validated by a measurement of the yield of (W/Z)Z production with Z → $ b\overline{b} $ in the same final states as for the Higgs boson search, from which the ratio of the observed signal yield to the Standard Model expectation is found to be 0.74 ± 0.09 (stat.) ± 0.14 (syst.).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of the W W + W Z cross section and limits on anomalous triple gauge couplings using final states with one lepton, missing transverse momentum, and two jets with the ATLAS detector at $ \sqrt{s}=7 $ TeV

The production of a W boson decaying to eν or μν in association with a W or Z boson decaying to two jets is studied using 4.6 fb -1 of proton-proton collision data at $ \sqrt{s}$ =7 TeV recorded with the ATLAS detector at the LHC. The combined WW + WZ cross section is measured with a significance of 3.4σ and is found to be 68 ± 7 (stat.)±19 (syst.) pb , in agreement with the Standard Model expectation of 61.1 ± 2.2 pb . The distribution of the transverse momentum of the dijet system is used to set limits on anomalous contributions to the triple gauge coupling vertices and on parameters of an effective-field-theory model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗