Search for high-mass dilepton resonances using139 fb −1 of p p collision data collected at √ s = 13 TeV with the ATLAS detectorThe ATLAS Collaboration A search for high-mass dielectron and dimuon resonances in the mass range of 250 GeV to 6 TeV is presented. The data were recorded by the ATLAS experiment in proton-proton collisions at a centre-of-mass energy of √ s = 13 TeV during Run 2 of the Large Hadron Collider and correspond to an integrated luminosity of 139 fb −1 . A functional form is fitted to the dilepton invariant-mass distribution to model the contribution from background processes, and a generic signal shape is used to determine the significance of observed deviations from this background estimate. No significant deviation is observed and upper limits are placed at the 95% confidence level on the fiducial cross-section times branching ratio for various resonance width hypotheses. The derived limits are shown to be applicable to spin-0, spin-1 and spin-2 signal hypotheses. For a set of benchmark models, the limits are converted into lower limits on the resonance mass and reach 4.5 TeV for the E 6 -motivated Z ψ boson. Also presented are limits on Heavy Vector Triplet model couplings.ATLAS [14-16] is a multipurpose detector with a forward-backward symmetric cylindrical geometry with respect to the LHC beam axis.1 The innermost layers consist of tracking detectors in the pseudorapidity range |η| < 2.5. This inner detector (ID) is surrounded by a thin superconducting solenoid that provides a 1 ATLAS uses a right-handed coordinate system with its origin at the nominal interaction point (IP) in the centre of the detector and the z-axis along the beam pipe. The x-axis points from the IP to the centre of the LHC ring, and the y-axis points upwards. Cylindrical coordinates (r, φ) are used in the transverse plane, φ being the azimuthal angle around the z-axis. The pseudorapidity is defined in terms of the polar angle θ as η = − ln tan(θ/2). Angular distance is measured in units of ∆R ≡ (∆η) 2 + (∆φ) 2 .

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Measurement of the production cross section of prompt J/ψ mesons in association with a W ± boson in pp collisions at √ s = 7 TeV with the ATLAS detectorThe ATLAS collaboration E-mail: atlas.publications@cern.ch Abstract: The process pp → W ± J/ψ provides a powerful probe of the production mechanism of charmonium in hadronic collisions, and is also sensitive to multiple parton interactions in the colliding protons. Using the 2011 ATLAS dataset of 4.5 fb −1 of √ s = 7 TeV pp collisions at the LHC, the first observation is made of the production of W ± + prompt J/ψ events in hadronic collisions, using W ± → µν µ and J/ψ → µ + µ − . A yield of 27.4 +7.5 −6.5 W ± + prompt J/ψ events is observed, with a statistical significance of 5.1σ. The production rate as a ratio to the inclusive W ± boson production rate is measured, and the double parton scattering contribution to the cross section is estimated. The ATLAS collaboration 20 IntroductionStudy of the production of a W boson in association with a prompt J/ψ meson offers new tests of Quantum Chromodynamics (QCD) at the perturbative/non-perturbative boundary as well as developing the framework for future probes of the Higgs sector and beyond-thestandard-model searches in such final states. Perturbative calculations of heavy quarkonium production in hadronic collisions distinguish between terms that produce a heavy quark system (QQ) in a colour-singlet (CS) or a colour-octet (CO) state. The relative importance of these terms for inclusive J/ψ production is a subject of debate [1][2][3][4][5][6][7]. In the case of prompt J/ψ production in association with a W ± boson, the relative contributions of CS and CO processes differ from the inclusive process. Some theoretical studies [8,9] suggest W ± + prompt J/ψ production should be dominated by colour-octet processes, and thus be a distinctive test of the non-relativistic QCD (NRQCD) framework [10,11]. In contrast, recent work [12] suggests that in 7 TeV pp collisions, CO and CS (in particular, electromagnetic W ± γ * →W ± J/ψ) contributions to the W ± + prompt J/ψ cross section are comparable. Measurements of the production cross sections can help distinguish between these models. A search for the related processes W ± +Υ(1S) and Z + Υ(1S) performed by the CDF experiment saw no excess of events above the expected background and set upper limits on the production rate [13].Observation and measurement of W ± + prompt J/ψ production for the first time represents a step in our understanding toward measurements of the Higgs boson in rare quarkonia and associated vector boson decay modes, first proposed in ref. [14]. Recent -1 - JHEP04(2014)172phenomenological studies [15] have emphasised the value of these rare decay modes to provide a unique probe of the Higgs boson charm couplings. Such final states can also be sensitive probes of beyond-the-standard-model (BSM) frameworks. The presence of an anomalous rate of W ± /Z + prompt J/ψ/Υ associated production over standard model predictions can, for example, be an indication of a sig...

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We present a measurement of the forward-backward asymmetry in top quark-antiquark production using the full Tevatron Run II data set collected by the D0 experiment at Fermilab. The measurement is performed in lepton þ jets final states using a new kinematic fitting algorithm for events with four or more jets and a new partial reconstruction algorithm for events with only three jets. Corrected for detector acceptance and resolution effects, the asymmetry is evaluated to be A FB ¼ ð10.6 AE 3.0Þ%. Results are consistent with the standard model predictions which range from 5.0% to 8.8%. We also present the dependence of the asymmetry on the invariant mass of the top quark-antiquark system and the difference in rapidities of the top quark and antiquark.