Explore the vast range of titles available.

The jet energy scale, jet energy resolution, and their systematic uncertainties are measured for jets reconstructed with the ATLAS detector in 2012 using proton-proton data produced at a centre-of-mass energy of 8 TeV with an integrated luminosity of [Formula omitted]. Jets are reconstructed from clusters of energy depositions in the ATLAS calorimeters using the anti- [Formula omitted] algorithm. A jet calibration scheme is applied in multiple steps, each addressing specific effects including mitigation of contributions from additional proton-proton collisions, loss of energy in dead material, calorimeter non-compensation, angular biases and other global jet effects. The final calibration step uses several in situ techniques and corrects for residual effects not captured by the initial calibration. These analyses measure both the jet energy scale and resolution by exploiting the transverse momentum balance in [Formula omitted] + jet, Z + jet, dijet, and multijet events. A statistical combination of these measurements is performed. In the central detector region, the derived calibration has a precision better than 1% for jets with transverse momentum [Formula omitted] 1500 GeV, and the relative energy resolution is [Formula omitted] for [Formula omitted] and [Formula omitted] for [Formula omitted]. The calibration scheme for jets with radius parameter [Formula omitted], for which jets receive a dedicated calibration of the jet mass, is also discussed.

Results are presented from the measurement by ATLAS of long-range ( [Formula omitted]) dihadron angular correlations in [Formula omitted] and 13 TeV pp collisions containing a Z boson. The analysis is performed using 19.4 [Formula omitted] of [Formula omitted] TeV data recorded during Run 1 of the LHC and 36.1 [Formula omitted] of [Formula omitted] TeV data recorded during Run 2. Two-particle correlation functions are measured as a function of relative azimuthal angle over the relative pseudorapidity range [Formula omitted] for different intervals of charged-particle multiplicity and transverse momentum. The measurements are corrected for the presence of background charged particles generated by collisions that occur during one passage of two colliding proton bunches in the LHC. Contributions to the two-particle correlation functions from hard processes are removed using a template-fitting procedure. Sinusoidal modulation in the correlation functions is observed and quantified by the second Fourier coefficient of the correlation function, [Formula omitted], which in turn is used to obtain the single-particle anisotropy coefficient [Formula omitted]. The [Formula omitted] values in the Z-tagged events, integrated over [Formula omitted] GeV, are found to be independent of multiplicity and [Formula omitted], and consistent within uncertainties with previous measurements in inclusive pp collisions. As a function of charged-particle [Formula omitted], the Z-tagged and inclusive [Formula omitted] values are consistent within uncertainties for [Formula omitted] GeV.

The results of a search for direct pair production of top squarks in events with two opposite-charge leptons (electrons or muons) are reported, using [Formula omitted] of integrated luminosity from proton-proton collisions at [Formula omitted] TeV collected by the ATLAS detector at the Large Hadron Collider. To cover a range of mass differences between the top squark [Formula omitted] and lighter supersymmetric particles, four possible decay modes of the top squark are targeted with dedicated selections: the decay [Formula omitted] into a b-quark and the lightest chargino with [Formula omitted], the decay [Formula omitted] into an on-shell top quark and the lightest neutralino, the three-body decay [Formula omitted] and the four-body decay [Formula omitted]. No significant excess of events is observed above the Standard Model background for any selection, and limits on top squarks are set as a function of the [Formula omitted] and [Formula omitted] masses. The results exclude at 95% confidence level [Formula omitted] masses up to about 720 GeV, extending the exclusion region of supersymmetric parameter space covered by previous searches.

Measurements of transverse energy-energy correlations and their associated asymmetries in multi-jet events using the ATLAS detector at the LHC are presented. The data used correspond to [Formula omitted] proton-proton collisions with an integrated luminosity of 20.2 [Formula omitted]. The results are presented in bins of the scalar sum of the transverse momenta of the two leading jets, unfolded to the particle level and compared to the predictions from Monte Carlo simulations. A comparison with next-to-leading-order perturbative QCD is also performed, showing excellent agreement within the uncertainties. From this comparison, the value of the strong coupling constant is extracted for different energy regimes, thus testing the running of [Formula omitted] predicted in QCD up to scales over [Formula omitted]. A global fit to the transverse energy-energy correlation distributions yields [Formula omitted], while a global fit to the asymmetry distributions yields a value of [Formula omitted].

This paper presents single lepton and dilepton kinematic distributions measured in dileptonic [Formula omitted] events produced in 20.2 [Formula omitted] of [Formula omitted] TeV pp collisions recorded by the ATLAS experiment at the LHC. Both absolute and normalised differential cross-sections are measured, using events with an opposite-charge [Formula omitted] pair and one or two b-tagged jets. The cross-sections are measured in a fiducial region corresponding to the detector acceptance for leptons, and are compared to the predictions from a variety of Monte Carlo event generators, as well as fixed-order QCD calculations, exploring the sensitivity of the cross-sections to the gluon parton distribution function. Some of the distributions are also sensitive to the top quark pole mass; a combined fit of NLO fixed-order predictions to all the measured distributions yields a top quark mass value of [Formula omitted] GeV, where the three uncertainties arise from data statistics, experimental systematics, and theoretical sources.

Observables sensitive to the anomalous production of events containing hadronic jets and missing momentum in the plane transverse to the proton beams at the Large Hadron Collider are presented. The observables are defined as a ratio of cross sections, for events containing jets and large missing transverse momentum to events containing jets and a pair of charged leptons from the decay of a [Formula omitted] boson. This definition minimises experimental and theoretical systematic uncertainties in the measurements. This ratio is measured differentially with respect to a number of kinematic properties of the hadronic system in two phase-space regions; one inclusive single-jet region and one region sensitive to vector-boson-fusion topologies. The data are found to be in agreement with the Standard Model predictions and used to constrain a variety of theoretical models for dark-matter production, including simplified models, effective field theory models, and invisible decays of the Higgs boson. The measurements use 3.2 fb [Formula omitted] of proton-proton collision data recorded by the ATLAS experiment at a centre-of-mass energy of 13 [Formula omitted] and are fully corrected for detector effects, meaning that the data can be used to constrain new-physics models beyond those shown in this paper.

This paper presents a study of [Formula omitted] and [Formula omitted] triboson production using events from proton-proton collisions at a centre-of-mass energy of [Formula omitted] recorded with the ATLAS detector at the LHC and corresponding to an integrated luminosity of 20.2 fb [Formula omitted]. The [Formula omitted] production cross-section is determined using a final state containing an electron, a muon, a photon, and neutrinos ( [Formula omitted]). Upper limits on the production cross-section of the [Formula omitted] final state and the [Formula omitted] and [Formula omitted] final states containing an electron or a muon, two jets, a photon, and a neutrino ( [Formula omitted] or [Formula omitted]) are also derived. The results are compared to the cross-sections predicted by the Standard Model at next-to-leading order in the strong-coupling constant. In addition, upper limits on the production cross-sections are derived in a fiducial region optimised for a search for new physics beyond the Standard Model. The results are interpreted in the context of anomalous quartic gauge couplings using an effective field theory. Confidence intervals at 95% confidence level are derived for the 14 coupling coefficients to which [Formula omitted] and [Formula omitted] production are sensitive.

This paper presents a study of the production of WW or WZ boson pairs, with one W boson decaying to [Formula omitted] or [Formula omitted] and one W or Z boson decaying hadronically. The analysis uses [Formula omitted] of [Formula omitted]pp collision data, collected by the ATLAS detector at the Large Hadron Collider. Cross-sections for WW / WZ production are measured in high- [Formula omitted] fiducial regions defined close to the experimental event selection. The cross-section is measured for the case where the hadronically decaying boson is reconstructed as two resolved jets, and the case where it is reconstructed as a single jet. The transverse momentum distribution of the hadronically decaying boson is used to search for new physics. Observations are consistent with the Standard Model predictions, and 95% confidence intervals are calculated for parameters describing anomalous triple gauge-boson couplings.

The distributions of transverse momentum and longitudinal momentum fraction of charged particles in jets are measured in Pb+Pb and pp collisions with the ATLAS detector at the LHC. The distributions are measured as a function of jet transverse momentum and rapidity. The analysis utilises an integrated luminosity of 0.14 nb [Formula omitted] of Pb+Pb data and 4.0 pb [Formula omitted] of pp data collected in 2011 and 2013, respectively, at the same centre-of-mass energy of 2.76 TeV per colliding nucleon pair. The distributions measured in pp collisions are used as a reference for those measured in Pb+Pb collisions in order to evaluate the impact on the internal structure of jets from the jet energy loss of fast partons propagating through the hot, dense medium created in heavy-ion collisions. Modest but significant centrality-dependent modifications of fragmentation functions in Pb+Pb collisions with respect to those in pp collisions are seen. No significant dependence of modifications on jet [Formula omitted] and rapidity selections is observed except for the fragments with the highest transverse momenta for which some reduction of yields is observed for more forward jets.

High-precision measurements by the ATLAS Collaboration are presented of inclusive [Formula omitted], [Formula omitted] and [Formula omitted] ( [Formula omitted]) Drell-Yan production cross sections at the LHC. The data were collected in proton-proton collisions at [Formula omitted] with an integrated luminosity of [Formula omitted]. Differential [Formula omitted] and [Formula omitted] cross sections are measured in a lepton pseudorapidity range [Formula omitted]. Differential [Formula omitted] cross sections are measured as a function of the absolute dilepton rapidity, for [Formula omitted], for three intervals of dilepton mass, [Formula omitted], extending from 46 to [Formula omitted]. The integrated and differential electron- and muon-channel cross sections are combined and compared to theoretical predictions using recent sets of parton distribution functions. The data, together with the final inclusive [Formula omitted] scattering cross-section data from H1 and ZEUS, are interpreted in a next-to-next-to-leading-order QCD analysis, and a new set of parton distribution functions, ATLAS-epWZ16, is obtained. The ratio of strange-to-light sea-quark densities in the proton is determined more accurately than in previous determinations based on collider data only, and is established to be close to unity in the sensitivity range of the data. A new measurement of the CKM matrix element [Formula omitted] is also provided.