Measurements of the cross sections of the production of pairs of electroweak gauge bosons at the LHC constitute stringent tests of the electroweak sector of the Standard Model and provide a model-independent means to search for new physics at the TeV scale. The ATLAS collaboration has performed detailed measurements of integrated and differential cross sections of the production of heavy...
We present predictions for diboson production (with exact decays) that are next-to-next-to-leading order (NNLO) accurate and consistently matched to a parton shower (NNLOPS). The matching is achieved by upgrading the NLO WW+j calculation with MiNLO, in such a way that NLO accuracy is guaranteed for W+W- inclusive observables and by then performing a reweighting of the WWJ-MiNLO events,...
Measurements of the cross sections of the production of three electroweak gauge bosons and of vector-boson scattering processes at the LHC constitute stringent tests of the electroweak sector of the Standard Model and provide a model-independent means to search for new physics at the TeV scale. The ATLAS collaboration searched for the production of three W bosons or of a W boson and a photon...
The most recent results on the production of single W and Z bosons with two jets at high invariant mass at centre-of-mass energies of 7, 8 and 13 TeV are presented. Integrated and differential cross sections are measured in many different phase space regions with varying degree of sensitivity to the electroweak production in vector boson fusion. The cross section for the electroweak W boson...
The production of massive vector boson pairs is a key process for the understanding of the non-abelian gauge structure of the standard model and for the comprehension of the electroweak symmetry breaking mechanism. In this presentation, we will report the most recent inclusive and differential measurements of multiboson production with data collected by the CMS. The recent study of the...
In ultra-peripheral heavy-ion collisions the ions encounter with such a large impact parameter that no strong interaction can take place. However, the photons produced by the colliding ion can interact either with the other nucleus or with a photon from the another nucleus. The former corresponds to photoproduction studied earlier in electron-proton collisions at HERA but with a nuclear...
Muon reconstruction and identification play a fundamental role in many analyses of central importance in the LHC run-2 Physics pro- gramme. The algorithms and the criteria used in ATLAS for the re- construction and identification of muons with transverse momentum from a few GeV to the TeV scale will be presented. Their performance is measured in data based on the decays of Z and J/ψ to pair of...
Isolated photons with high transverse energy have been studied in
deep inelastic $ep$ scattering with the ZEUS detector at HERA, using
an integrated luminosity of $326\, \mathrm{pb}^{-1}$ in the range of
exchanged-photon virtuality $10 - 350 \,\, \mathrm{GeV}^2$. Outgoing
isolated photons with transverse energy $4< E_T^\gamma< 15$ GeV and
pseudorapidity $-0.7 < \eta^\gamma < 0.9$ were measured...
We report a measurement of the cross section for K^0_S pair production in single-tag two-photon collisions, gamma gamma → K^0_S K^0_S for Q^2 up to 30 GeV^2, where Q^2 is the negative of the invariant mass squared of the tagged photon. The measurement covers the kinematic range 1.0 GeV < W < 2.6 GeV and |cos theta|<1.0 for the total energy and kaon scattering angle, respectively, in the...
In a recent article (1801.06113), we discussed the possibility of using simple matrix elements to produce probabilities of rearranging the colour chains in dipole shower algorithms. Due to the changed density of larger and smaller dipole chains, particle spectra and standard observables are modified. In the talk, I will discuss the idea and the consequences for tuning and the soft model of...
Over the years many different types of fits for the strong coupling constant have been performed. However one high precision result that currently significantly differs from the world average are results from event shapes at electron positron colliders. One possible source for the difference in these results could be the degeneracy between the fit of the strong coupling constant and...
Calculations of jet substructure observables which are accurate beyondleading-logarithmic accuracy have recently become available. Such observables are significant not only for probing a new regime of QCD at a hadron collider, but also for improving the understanding of jet substructure properties that are used in many studies at the Large Hadron Collider. In this talk, we discuss first...
In order to exploit the abundance of high momentum heavy particles produced at LHC (top, W/Z and Higgs) and decaying hadronically, the study of jet substucture has become increasingly important throughout a wide array of searches and measurements. The latest ATLAS results in terms of jet substructure measurements and calibrations are presented including studies of performance sensitivity to...
We present results on measurements of characteristics of events with jets, from jet-charge over investigations of shapes to jet mass distributions, and angular correlations in multi-jet events. The measurements are compared to theoretical predictions including those matched to parton shower and hadronization.
The production of jets and electroweak gauge bosons in association with a jet, V+jet, constitute two important classes of standard-candle processes at the LHC. Owing to the large event rate and the direct sensitivity to the strong coupling constant and the gluon PDF, they provide an ideal testing ground for our understanding of perturbative QCD in a hadron-collider environment.
I give an...
We present the first threshold and jet radius jointly resummed cross section for single-inclusive hadronic jet production. We work at next-to-leading logarithmic accuracy and our framework allows for a systematic extension beyond the currently achieved precision. Longstanding numerical issues are overcome by performing the resummation directly in momentum space within Soft Collinear Effective...
We present measurements of differential jet cross sections over a wide range in transverse momenta from inclusive jets to multi-jet final states. Studies on the impact that these measurements have on the determination of the strong coupling alpha_s as well as on parton density functions are reported.
The production of inclusive jets and di-jets at hadron colliders provides a stringent test of perturbative QCD at the highest energies. The process can also be used to probe the gluon density function of the proton. The ATLAS collaboration has measured the inclusive jet production cross section in 20.3 /fb of data collected at a center-of-mass energy of 8TeV and in 3.2 /fb of data collected at...
The production of jets in association with vector bosons is an important process to study QCD in a multi-scale environment. The ATLAS collaboration has performed measurements of vector boson+jets cross sections, differential in several kinematic variables, in proton-proton collision data taken at center-of-mass energies of 8TeV and 13TeV. The measurements are compared to state-of-the art...
The production of vector bosons (W, Z, gamma) in association with jets is a stringent test of perturbative QCD and is a background process in searches for new physics. Total and differential cross-section measurements of vector bosons produced in association with jets in proton-proton collisions performed by the CMS collaboration at the LHC are presented. The measurements are compared to the...
I will present the current status of the determination of the QCD coupling $\alpha_s$ from the 15 methods where high-precision theoretical calculations and experimental measurements are (or will be) available including, among others: (i) lattice QCD, (ii) $\tau$ hadronic decays, (iii) soft parton-to-hadron fragmentation functions, (iv) proton structure functions, (v) e+e- event shapes and jet...
I will present a method for the computation of logarithmically
enhanced terms at all orders for observables featuring kinematic cancellations
away from the Sudakov limit. I will describe the approach in the context of observables of interest at colliders, and comment on extensions to more general cases.
We study lepton-pair production in association with bottom quarks at the LHC,
and present the predictions obtained at next-to-leading order in QCD,
both at fixed order and matched with a QCD parton shower, for several differential distributions.
We discuss the estimate of the theoretical uncertainties
and consider the dependence on the perturbative QCD scales (renormalisation, factorisation...
With the high integrated luminosities recorded at the LHC and the very good understanding of the ATLAS detector, it is possible to measure electroweak observables to the highest precision. In this talk, we review the measurement of the W boson mass using data, collected at 7 TeV. Special focus is drawn on a discussion of the modeling uncertainties and the physics potential of the latest low-mu...
State-of-the-art theoretical predictions accurate to next-to-leading order QCD interfaced with Pythia8, Herwig, and Sherpa event generators are tested by comparing the unfolded ttbar differential data collected with the CMS detector at 8 and 13 TeV. These predictions are also compared with the underlying event activity distributions in ttbar events using CMS proton-proton data collected at a...
We calculate the different angular distribution spectra of $\gamma$-jet and jet-jet pairs in associated $\gamma+2$ jet production at the energies of the Tevatron and the LHC Colliders in the leading order approximation of the parton Reggeization approach [1-3]. Last one is based on high-energy factorization ($k_T-$factorization) and L.N. Lipatov's Effective Theory of Reggeized gluon and...
We study azimuthal ratios in Mueller-Navalet jets after imposing a rapidity veto constraint. In particular, we restrict the minijet radiation activity by not allowing subsequent emissions to be closer in rapidity than some fixed value b, the value of the rapidity veto. Previous studies in the literature suggest that for the NLL BFKL Green's function a rapidity veto with a value of two units of...
To simplify the calculation of DIS processes, many papers employed a form of the leptonic tensor which will lead to wrong results when the transverse momentum or rapidity of a final-state hadron is measured in the laboratory frame. Among these papers are there some highly cited ones and those employed by the event generators. To this end, many experimental data need to be reanalysed. I will...
The $p_\perp$ dependence of the nuclear modification factor $R_{AA}$ measured in PbPb collisions at the LHC exhibits a universal shape, which can be very well reproduced in a simple energy loss model based on the Baier-Dokshitzer-Mueller-Peigné-Schiff medium-induced gluon spectrum. The scaling is observed for various hadron species ($h^\pm$, $D$, $J/\psi$) in different centrality classes and...
