The leptonic and inclusive hadronic decay branching fractions of the W boson are measured using proton-proton collision data collected at $\sqrt{s} =$ 13 TeV by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Events characterized by the production of one or two W bosons are selected and categorized based on the multiplicity and flavor of reconstructed leptons, the number of jets, and the number of jets identified as originating from the hadronization of b quarks. A binned maximum likelihood estimate of the W boson branching fractions is performed simultaneously in each event category. The measured branching fractions of the W boson decaying into electron, muon, and tau lepton final states are (10.83 $\pm$ 0.10)%, (10.94 $\pm$ 0.08)%, and (10.77 $\pm$ 0.21)%, respectively, consistent with lepton flavor universality for the weak interaction. The average leptonic and inclusive hadronic decay branching fractions are estimated to be (10.89 $\pm$ 0.08)% and (67.32 $\pm$ 0.23)%, respectively. Based on the hadronic branching fraction, three standard model quantities are subsequently derived: the sum of squared elements in the first two rows of the Cabibbo-Kobayashi-Maskawa (CKM) matrix $\sum_{ij}\vert V_{ij}\vert^{2}$ = 1.984 $\pm$ 0.021, the CKM element $\vert V_\mathrm{cs}\vert$ = 0.967 $\pm$ 0.011, and the strong coupling constant at the W boson mass scale, $\alpha_\mathrm{S}(m^2_\mathrm{W})$ = 0.095 $\pm$ 0.033.
Summary of the impacts of each source of uncertainty (quoted as a percent of the total systematic uncertainty) for each W branching fraction. Whenever multiple NPs impact a common source of systematic uncertainty, each component is varied independently and the range of impacts is given.
Values of the W boson decay branching fractions based on CMS measurement.
Ratios of W boson leptonic branching fractions.
The inclusive cross section for top quark pair production is measured in proton-proton collisions at sqrt(s) = 7 and 8 TeV, corresponding to 5.0 and 19.7 invers-femtobarns, respectively, with the CMS experiment at the LHC. The cross sections are measured in the electron-muon channel using a binned likelihood fit to multi-differential final state distributions related to identified b quark jets and other jets in the event. The measured cross section values are 173.6 +/- 2.1 (stat) +4.5-4.0 (syst) +/- 3.8 (lumi) pb at sqrt(s) = 7 TeV, and 244.9 +/- 1.4 (stat) +6.3-5.5 (syst) +/- 6.4 (lumi) pb at sqrt(s) = 8 TeV, in good agreement with QCD calculations at next-to-next-to-leading-order accuracy. The ratio of the cross sections measured at 7 and 8 TeV is determined, as well as cross sections in the fiducial regions defined by the acceptance requirements on the two charged leptons in the final state. The cross section results are used to determine the top quark pole mass via the dependence of the theoretically predicted cross section on the mass, giving a best result of 173.8 +1.7-1.8 GeV. The data at sqrt(s) = 8 TeV are also used to set limits, for two neutralino mass values, on the pair production of supersymmetric top squarks with masses close to the top quark mass.
Measurement of the visible $t\bar{t}$ production cross-section in $pp$ collisions at $\sqrt{s} = 7$ and $8$ TeV. The visible cross section is defined for events containing an oppositely charged $\rm{e}\mu$ pair from the decay chain ${\rm t} \rightarrow {\rm W b} \rightarrow {\ell} \nu {\rm b}$ (including ${\rm W} \rightarrow \tau \nu \rightarrow {\ell} \nu \nu \nu$) and with both leptons satisfying $p_T > 20\, \rm{GeV}$ and $|{\eta}| < 2.4$.
Measurement of the inclusive $t\bar{t}$ production cross-section in $pp$ collisions at $\sqrt{s} = 7$ and $8$ TeV.
Top quark pole mass at NNLO+NNLL extracted by comparing the measured $t\bar{t}$ production cross sections at 7 and 8 TeV with predictions employing different PDF sets. The uncertainties of the CT14 PDF set are scaled to 68% confidence level.
A search is reported for a light pseudoscalar Higgs boson decaying to a pair of tau leptons, produced in association with a b b-bar pair, in the context of two-Higgs-doublet models. The results are based on pp collision data at a centre-of-mass energy of 8 TeV collected by the CMS experiment at the LHC and corresponding to an integrated luminosity of 19.7 inverse femtobarns. Pseudoscalar boson masses between 25 and 80 GeV are probed. No evidence for a pseudoscalar boson is found and upper limits are set on the production cross section times branching fraction to tau pairs between 7 and 39 pb at the 95% confidence level. This excludes pseudoscalar A bosons with masses between 25 and 80 GeV, with standard model-like Higgs boson negative couplings to down-type fermions, produced in association with b b-bar pairs, in Type-II, two-Higgs-doublet models.
Expected and observed 95 % CL combined upper limits in pb on pseudoscalar Higgs bosons produced in association with bb pairs, along with their 1 and 2 standard deviation uncertainties.
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