Combination of the W boson polarization measurements in top quark decays using ATLAS and CMS data at $\sqrt{s}=$ 8 TeV

Abstract

The combination of measurements of the W boson polarization in top quark decays performed by the ATLAS and CMS Collaborations is presented. The measurements are based on proton-proton collision data produced at the LHC at a centre-of-mass energy of 8 TeV, and corresponding to an integrated luminosity of about 20 fb${}^{-1}$ for each experiment. The measurements used events containing one lepton and having different jet multiplicities in the final state. The results are quoted as fractions of W bosons with longitudinal ($F_0$), left-handed ($F_{\mathrm{L}}$), or right-handed ($F_{\mathrm{R}}$) polarizations. The resulting combined measurements of the polarization fractions are $F_0=$ 0.693 $\pm$ 0.014 and $F_{\mathrm{L}}=$ 0.315 $\pm$ 0.011. The fraction $F_{\mathrm{R}}$ is calculated from the unitarity constraint to be $F_{\mathrm{R}}=-$0.008 $\pm$ 0.007. These results are in agreement with the standard model predictions at next-to-next-to-leading order in perturbative quantum chromodynamics and represent an improvement in precision of 25 (29)% for $F_0$ ($F_{\mathrm{L}}$) with respect to the most precise single measurement. A limit on anomalous right-handed vector ($V_{\text{R}}$), and left- and right-handed tensor ($g_{\text{L}},g_{\text{R}}$) tWb couplings is set while fixing all others to their standard model values. The allowed regions are [$-$0.11, 0.16] for $V_{\text{R}}$, [$-$0.08, 0.05] for $g_{\text{L}}$, and [$-$0.04, 0.02] for $g_{\text{R}}$, at 95% confidence level. Limits on the corresponding Wilson coefficients are also derived.

arXiv commentReplaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/TOP-19-004 (CMS Public Pages) and https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2018-02 (ATLAS Public Pages)

References in corpus (40)

• PYTHIA 6.4 Physics and Manual
• PYTHIA 6.2 Physics and Manual
• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• FastJet user manual
• Parton distributions for the LHC
• A Unified Approach to the Classical Statistical Analysis of Small Signals
• A general framework for implementing NLO calculations in shower Monte Carlo programs: the POWHEG BOX
• A New Method for Combining NLO QCD with Shower Monte Carlo Algorithms
• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• New parton distributions for collider physics
• HERWIG 6.5: an event generator for Hadron Emission Reactions With Interfering Gluons (including supersymmetric processes)
• Parton distributions with LHC data
• Matching NLO QCD computations and parton shower simulations
• Implications of CTEQ global analysis for collider observables
• A Positive-Weight Next-to-Leading-Order Monte Carlo for Heavy Flavour Hadroproduction
• Particle-flow reconstruction and global event description with the CMS detector
• Tuning Monte Carlo Generators: The Perugia Tunes
• NLO single-top production matched with shower in POWHEG: s- and t-channel contributions
• CompHEP 4.4 - Automatic Computations from Lagrangians to Events
• Topological cell clustering in the ATLAS calorimeters and its performance in LHC Run 1
• The PDF4LHC Working Group Interim Recommendations
• Luminosity determination in pp collisions at $\sqrt{s}$ = 8 TeV using the ATLAS detector at the LHC
• A minimal set of top anomalous couplings
• Impact of Heavy Quark Masses on Parton Distributions and LHC Phenomenology
• The PDF4LHC Working Group Interim Report
• Measurement of the differential cross section for top quark pair production in pp collisions at sqrt(s) = 8 TeV
• Helicity fractions of W bosons from top quark decays at NNLO in QCD
• Probing anomalous Wtb couplings in top pair decays
• A likelihood-based reconstruction algorithm for top-quark pairs and the KLFitter framework
• Measurement of the W boson polarization in top quark decays with the ATLAS detector
• Measurement of the top quark mass in the $t\bar{t}\to$ dilepton channel from $\sqrt{s}=8$ TeV ATLAS data
• Fiducial, total and differential cross-section measurements of $t$-channel single top-quark production in $pp$ collisions at 8 TeV using data collected by the ATLAS detector
• On the combination of correlated estimates of a physics observable
• A General Analysis of Wtb anomalous Couplings
• EFTfitter---A tool for interpreting measurements in the context of effective field theories
• Measurement of the W boson helicity fractions in the decays of top quark pairs to lepton + jets final states produced in pp collisions at sqrt(s) = 8 TeV
• Measurement of the $W$ boson polarisation in $t\bar{t}$ events from $pp$ collisions at $\sqrt{s}$ = 8 TeV in the lepton+jets channel with ATLAS
• Measurement of the single top quark and antiquark production cross sections in the $t$ channel and their ratio in proton-proton collisions at $\sqrt{s}=$ 13 TeV
• Measurement of the W-boson helicity in top-quark decays from ttbar production in lepton+jets events in pp collisions at sqrt(s) = 7 TeV
• Measurement of the W boson helicity in events with a single reconstructed top quark in pp collisions at sqrt(s) = 8 TeV

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• Measurement of Higgs boson self-couplings through $2\to 3$ vector bosons scattering in future muon colliders
• Reconstruction of Unstable Heavy Particles Using Deep Symmetry-Preserving Attention Networks
• Amplitude-assisted tagging of longitudinally polarised bosons using wide neural networks
• Reconstruction of Missing Resonances Combining Nearest Neighbors Regressors and Neural Network Classifiers
• A combined approach to the analysis of space and ground experimental data within a simplified E6SSM
• $CP$ violation in the $HZZ$ vertex and left-right asymmetries
• Single-top quark physics at the LHC: from precision measurements to rare processes and top quark properties
• NLO EW and QCD corrections to polarized ZZ production in the four-charged-lepton channel at the LHC
• Probing top quark anomalous moments in $W$ boson associated single top quark production at the LHC using polarization and spin correlation
• First order electroweak radiative corrections to the decay of the polarised $W$ boson
• Probing effective operators in single top quark production in association with a lepton-neutrino pair
• W-boson helicity fractions in top decay as probes of dimension-6 and dimension-8 SMEFT operators
• $CP$-odd form factor in the $HWW$ vertex