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 .

The Large Hadron–Electron Collider (LHeC) is designed to move the field of deep inelastic scattering (DIS) to the energy and intensity frontier of particle physics. Exploiting energy-recovery technology, it collides a novel, intense electron beam with a proton or ion beam from the High-Luminosity Large Hadron Collider (HL-LHC). The accelerator and interaction region are designed for concurrent electron–proton and proton–proton operations. This report represents an update to the LHeC’s conceptual design report (CDR), published in 2012. It comprises new results on the parton structure of the proton and heavier nuclei, QCD dynamics, and electroweak and top-quark physics. It is shown how the LHeC will open a new chapter of nuclear particle physics by extending the accessible kinematic range of lepton–nucleus scattering by several orders of magnitude. Due to its enhanced luminosity and large energy and the cleanliness of the final hadronic states, the LHeC has a strong Higgs physics programme and its own discovery potential for new physics. Building on the 2012 CDR, this report contains a detailed updated design for the energy-recovery electron linac (ERL), including a new lattice, magnet and superconducting radio-frequency technology, and further components. Challenges of energy recovery are described, and the lower-energy, high-current, three-turn ERL facility, PERLE at Orsay, is presented, which uses the LHeC characteristics serving as a development facility for the design and operation of the LHeC. An updated detector design is presented corresponding to the acceptance, resolution, and calibration goals that arise from the Higgs and parton-density-function physics programmes. This paper also presents novel results for the Future Circular Collider in electron–hadron (FCC-eh) mode, which utilises the same ERL technology to further extend the reach of DIS to even higher centre-of-mass energies.

Searches for both resonant and nonresonant Higgs boson pair production are performed in the hh → bbττ, γγWW Ã final states using 20.3 fb −1 of pp collision data at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the Large Hadron Collider. No evidence of their production is observed and 95% confidence-level upper limits on the production cross sections are set. These results are then combined with the published results of the hh → γγbb, bbbb analyses. An upper limit of 0.69 (0.47) pb on the nonresonant hh production is observed (expected), corresponding to 70 (48) times the SM gg → hh cross section. For production via narrow resonances, cross-section limits of hh production from a heavy Higgs boson decay are set as a function of the heavy Higgs boson mass. The observed (expected) limits range from 2.1 (1.1) pb at 260 GeV to 0.011 (0.018) pb at 1000 GeV. These results are interpreted in the context of two simplified scenarios of the Minimal Supersymmetric Standard Model.

Study of the underlying event at forward rapidity in pp collisions at √ s = 0.9, 2.76, and 7 TeVThe CMS collaboration E-mail: cms-publication-committee-chair@cern.chAbstract: The underlying event activity in proton-proton collisions at forward pseudorapidity (−6.6 < η < −5.2) is studied with the CMS detector at the LHC, using a novel observable: the ratio of the forward energy density, dE/dη, for events with a chargedparticle jet produced at central pseudorapidity (|η jet | < 2) to the forward energy density for inclusive events. This forward energy density ratio is measured as a function of the central jet transverse momentum, p T , at three different pp centre-of-mass energies ( √ s = 0.9, 2.76, and 7 TeV). In addition, the √ s evolution of the forward energy density is studied in inclusive events and in events with a central jet. The results are compared to those of Monte Carlo event generators for pp collisions and are discussed in terms of the underlying event. Whereas the dependence of the forward energy density ratio on jet p T at each √ s separately can be well reproduced by some models, all models fail to simultaneously describe the increase of the forward energy density with √ s in both inclusive events and in events with a central jet.

Inclusive jet production cross-sections are measured in proton-proton collisions at a centre-of-mass energy of √ s = 8 TeV recorded by the ATLAS experiment at the Large Hadron Collider at CERN. The total integrated luminosity of the analysed data set amounts to 20.2 fb −1 . Double-differential cross-sections are measured for jets defined by the anti-k t jet clustering algorithm with radius parameters of R = 0.4 and R = 0.6 and are presented as a function of the jet transverse momentum, in the range between 70 GeV and 2.5 TeV and in six bins of the absolute jet rapidity, between 0 and 3.0. The measured cross-sections are compared to predictions of quantum chromodynamics, calculated at next-to-leading order in perturbation theory, and corrected for non-perturbative and electroweak effects. The level of agreement with predictions, using a selection of different parton distribution functions for the proton, is quantified. Tensions between the data and the theory predictions are observed. 5 Event and jet selection 5 6 Jet energy calibration and resolution 6 6.1 Jet reconstruction 6 6.2 Jet energy calibration 6 6.3 Jet energy scale uncertainties 7 6.4 Jet energy resolution and uncertainties 8 6.5 Jet angular resolution and uncertainties 97 Unfolding of detector effects 98 Propagation of the statistical and systematic uncertainties 10 9 Theoretical predictions 11 9.1 Next-to-leading-order QCD calculation 11 9.2 Electroweak corrections 13 9.3 Non-perturbative corrections Conclusion 27A Quantitative comparison of data to NLO QCD calculations with alternate correlation scenarios 29The ATLAS collaboration 37-1 - JHEP09(2017)020 1 IntroductionThe Large Hadron Collider (LHC) [1] at CERN, colliding protons on protons, provides a unique opportunity to explore the production of hadronic jets in the TeV energy range. In Quantum Chromodynamics (QCD), jet production can be interpreted as the fragmentation of quarks and gluons produced in a short-distance scattering process. The inclusive jet production cross-section (p + p → jet + X) gives valuable information about the strong coupling constant (α s ) and the structure of the proton. It is also among the processes directly testing the experimentally accessible space-time distances. Next-to-leading-order (NLO) perturbative QCD calculations [2,3] give quantitative predictions of the jet production cross-sections. Progress in next-to-next-to-leading-order (NNLO) QCD calculations has been made over the past several years [4][5][6][7][8][9]. After the completion of the first calculations of some sub-processes [10,11], the complete NNLO QCD inclusive jet cross-section calculation was published recently [12].As fixed-order QCD calculations only make predictions for the quarks and gluons associated with the short-distance scattering process, corrections for the fragmentation of these partons to particles need to be applied. The measurements can also be compared to Monte Carlo event generator predictions that directly simulate the particles entering the detector. These event gen...