607 research outputs found
Measurements of production cross sections in collisions at TeV with the ATLAS detector and limits on anomalous gauge boson self-couplings
No full textSee paper for full list of authors – 38 pages plus author list + cover pages (56 pages total), 16 figures, 9 tables. Submitted to Phys. Rev. D. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2014-02/International audienceThis paper presents measurements of production in collisions at a center-of-mass energy of 8 TeV. The gauge bosons are reconstructed using their leptonic decay modes into electrons and muons. The data were collected in 2012 by the ATLAS experiment at the Large Hadron Collider, and correspond to an integrated luminosity of 20.3 fb. The measured inclusive cross section in the detector fiducial region is 0.9 (stat.) (sys.) (lumi.) fb, for one leptonic decay channel. In comparison, the next-to-leading-order Standard Model expectation is 30.0 2.1 fb. Cross sections for and production and their ratio are presented as well as differential cross sections for several kinematic observables. Limits on anomalous triple gauge boson couplings are derived from the transverse mass spectrum of the system. From the analysis of events with a and a boson associated with two or more forward jets an upper limit at 95% confidence level on the scattering cross section of 0.63 fb, for each leptonic decay channel, is established, while the Standard Model prediction at next-to-leading order is 0.13 fb. Limits on anomalous quartic gauge boson couplings are also extracted
Measurement of the production of a boson in association with a charmed hadron in collisions at with the ATLAS detector
No full textThe production of a boson in association with a single charm quark is studied using 140 of proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider. The charm quark is tagged by a charmed hadron, reconstructed with a secondary-vertex fit. The boson is reconstructed from an electron/muon decay and the missing transverse momentum. The mesons reconstructed are and , where , , and , , and . The integrated and normalized differential cross-sections as a function of the pseudorapidity of the lepton from the boson decay, and of the transverse momentum of the meson, are extracted from the data using a profile likelihood fit. The measured fiducial cross-sections are , , , and . Results are compared with the predictions of next-to-leading-order quantum chromodynamics calculations performed using state-of-the-art parton distribution functions. The ratio of charm to anti-charm production cross-sections is studied to probe the - quark asymmetry and is found to be
Measurement of the production cross section in collisions at a centre-of-mass energy of = 13 TeV with the ATLAS experiment
No full textSee paper for full list of authors - 37 pages in total, author list starting page 21, 8 figures, 8 tables, submitted to Phys. Lett. B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2015-20/International audienceThe production of opposite-charge -boson pairs in proton-proton collisions at = 13 TeV is measured using data corresponding to 3.16 fb of integrated luminosity collected by the ATLAS detector at the CERN Large Hadron Collider in 2015. Candidate -boson pairs are selected by identifying their leptonic decays into an electron, a muon and neutrinos. Events with reconstructed jets are not included in the candidate event sample. The cross-section measurement is performed in a fiducial phase space close to the experimental acceptance and is compared to theoretical predictions. Agreement is found between the measurement and the most accurate calculations available
Test of the universality of and lepton couplings in -boson decays from events with the ATLAS detector
No full textThe Standard Model of particle physics encapsulates our current best
understanding of physics at the smallest scales. A fundamental axiom of this
theory is the universality of the couplings of the different generations of
leptons to the electroweak gauge bosons. The measurement of the ratio of the
rate of decay of bosons to -leptons and muons, , constitutes an important test of this
axiom. A measurement of this quantity with a novel technique using di-leptonic
events is presented based on 139 fb of data recorded with
the ATLAS detector in proton--proton collisions at TeV. Muons
originating from bosons and those originating from an intermediate
-lepton are distinguished using the lifetime of the -lepton,
through the muon transverse impact parameter, and differences in the muon
transverse momentum spectra. The value of is found to be and is in agreement with the
hypothesis of universal lepton couplings as postulated in the Standard Model.
This is the most precise measurement of this ratio, and the only such
measurement from the Large Hadron Collider, to date.Comment: 33 pages in total, author list starting page 17, 4 figures, 2 tables,
submitted to Nature Physics. All figures including auxiliary figures are
available at
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2018-2
Measurements of W(+/-)Z production cross sections in pp collisions at root s=8 TeV with the ATLAS detector and limits on anomalous gauge boson self-couplings
No full textThis paper presents measurements of W(+/-)Z production in pp collisions at a center-of-mass energy of 8 TeV. The gauge bosons are reconstructed using their leptonic decay modes into electrons and muons. The data were collected in 2012 by the ATLAS experiment at the Large Hadron Collider and correspond to an integrated luminosity of 20.3 fb(-1). The measured inclusive cross section in the detector fiducial region is sigma W(+/-)Z -> l'nu ll = 35.1 +/- 0.9(stat) +/- 0.8(sys) +/- 0.8(lumi) fb, for one leptonic decay channel. In comparison, the next-to-leading-order Standard Model expectation is 30.0 +/- 2.1 fb. Cross sections for W(+)Z and W(-)Z production and their ratio are presented as well as differential cross sections for several kinematic observables. Limits on anomalous triple gauge boson couplings are derived from the transverse mass spectrum of the W(+/-)Z system. From the analysis of events with a W and a Z boson associated with two or more forward jets an upper limit at 95% confidence level on the W(+/-)Z scattering cross section of 0.63 fb, for each leptonic decay channel, is established, while the Standard Model prediction at next-to-leading order is 0.13 +/- 0.01 fb. Limits on anomalous quartic gauge boson couplings are also extracted
Measurements of W+ W- production in decay topologies inspired by searches for electroweak supersymmetry
No full textThis paper presents a measurement of fiducial and differential cross-sections for W+W- production in proton–proton collisions at s=13 TeV with the ATLAS experiment at the Large Hadron Collider using a dataset corresponding to an integrated luminosity of 139 fb - 1 . Events with exactly one electron, one muon and no hadronic jets are studied. The fiducial region in which the measurements are performed is inspired by searches for the electroweak production of supersymmetric charginos decaying to two-lepton final states. The selected events have moderate values of missing transverse momentum and the ‘stransverse mass’ variable mT2 , which is widely used in searches for supersymmetry at the LHC. The ranges of these variables are chosen so that the acceptance is enhanced for direct W+W- production and suppressed for production via top quarks, which is treated as a background. The fiducial cross-section and particle-level differential cross-sections for six variables are measured and compared with two theoretical SM predictions from perturbative QCD calculations
Measurement of the and production cross sections in multilepton final states using 3.2 fb of collisions at = 13 TeV with the ATLAS detector
No full textSee paper for full list of authors - 22 pages plus author list + cover page (40 pages total), 8 figures, 5 tables. Submitted to Eur. Phys. J. C. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2015-22/International audienceA measurement of the and production cross sections in final states with either two same-charge muons, or three or four leptons (electrons or muons) is presented. The analysis uses a data sample of proton-proton collisions at TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015, corresponding to a total integrated luminosity of 3.2 fb. The inclusive cross sections are extracted using likelihood fits to signal and control regions, resulting in pb and pb, in agreement with the Standard Model predictions
Observation of photon-induced W+W− production in pp collisions at √s = 13 TeV using the ATLAS detector
No full textThis letter reports the observation of photon-induced production of W -boson pairs, γγ → W W . The
analysis uses 139 fb−1 of LHC proton–proton collision data taken at √s = 13 TeV recorded by the
ATLAS experiment during the years 2015–2018. The measurement is performed selecting one electron
and one muon, corresponding to the decay of the diboson system as W W → e±νμ∓ν final state. The
background-only hypothesis is rejected with a significance of well above 5 standard deviations consistent
with the expectation from Monte Carlo simulation. A cross section for the γγ → W W process of
3.13±0.31(stat.)±0.28(syst.) fb is measured in a fiducial volume close to the acceptance of the detector,
by requiring an electron and a muon of opposite signs with large dilepton transverse momentum and
exactly zero additional charged particles. This is found to be in agreement with the Standard Model
prediction
Measurements of W + W − + ≥ 1 jet production cross-sections in pp collisions at s = 13 TeV with the ATLAS detector
No full textAbstract: Fiducial and differential cross-section measurements of W+W− production in association with at least one hadronic jet are presented. These measurements are sensitive to the properties of electroweak-boson self-interactions and provide a test of perturbative quantum chromodynamics and the electroweak theory. The analysis is performed using proton-proton collision data collected at s = 13 TeV with the ATLAS experiment, corresponding to an integrated luminosity of 139 fb−1. Events are selected with exactly one oppositely charged electron-muon pair and at least one hadronic jet with a transverse momentum of pT> 30 GeV and a pseudorapidity of |η| < 4.5. After subtracting the background contributions and correcting for detector effects, the jet-inclusive W+W−+ ≥ 1 jet fiducial cross-section and W+W−+ jets differential cross-sections with respect to several kinematic variables are measured. These measurements include leptonic quantities, such as the lepton transverse momenta and the transverse mass of the W+W− system, as well as jet-related observables such as the leading jet transverse momentum and the jet multiplicity. Limits on anomalous triple-gauge-boson couplings are obtained in a phase space where interference between the Standard Model amplitude and the anomalous amplitude is enhanced
Measurement of boson angular distributions in events with high transverse momentum jets at 8 TeV using the ATLAS detector
No full textSee paper fo full list of authors. 38 pages in total, author list starting page 22, 5 figures, 6 tables, submitted to Phys. Lett. B, All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2015-16/International audienceThe boson angular distribution in events with high transverse momentum jets is measured using data collected by the ATLAS experiment from proton--proton collisions at a centre-of-mass energy 8 TeV at the Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb. The focus is on the contributions to + jets processes from real emission, which is achieved by studying events where a muon is observed close to a high transverse momentum jet. At small angular separations, these contributions are expected to be large. Various theoretical models of this process are compared to the data in terms of the absolute cross-section and the angular distributions of the muon from the leptonic decay
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