The production of W$^\pm$ bosons is studied in proton-lead (pPb) collisions at a nucleon-nucleon centre-of-mass energy of $\sqrt{s_\mathrm{NN}} =$ 8.16 TeV. Measurements are performed in the W$^\pm$ $\to$ $\mu^\pm\nu_\mu$ channel using a data sample corresponding to an integrated luminosity of 173.4 $\pm$ 8.7 nb$^{-1}$, collected by the CMS Collaboration at the LHC. The number of positively and negatively charged W bosons is determined separately in the muon pseudorapidity region in the laboratory frame $|\eta^\mu_\mathrm{lab}|$ $<$ 2.4 and transverse momentum $p_\mathrm{T}^\mu$ $>$ 25 GeV/$c$. The W$^\pm$ boson differential cross sections, muon charge asymmetry, and the ratios of W$^\pm$ boson yields for the proton-going over the Pb-going beam directions are reported as a function of the muon pseudorapidity in the nucleon-nucleon centre-of-mass frame. The measurements are compared to the predictions from theoretical calculations based on parton distribution functions (PDFs) at next-to-leading-order. The results favour PDF calculations that include nuclear modifications and provide constraints on the nuclear PDF global fits.
Muon charge asymmetry, $(N_{\mu}^{+} - N_{\mu}^{-})/(N_{\mu}^{+} + N_{\mu}^{-})$, as a function of the muon pseudorapidity in the centre-of-mass frame.
Differential production cross sections for $\textrm{pPb} \to W^{+} + X \to \mu^{+} \nu + X$ for positively charged muons of $p_T$ larger than 25 GeV$/c$, in nanobarns, as a function of the muon pseudorapidity in the centre-of-mass frame. The global normalisation uncertainty of 3.5% is listed separately.
Differential production cross sections for $\textrm{pPb} \to W^{-} + X \to \mu^{-} \bar{\nu} + X$ for negatively charged muons of $p_T$ larger than 25 GeV$/c$, in nanobarns, as a function of the muon pseudorapidity in the centre-of-mass frame. The global normalisation uncertainty of 3.5% is listed separately.
Measurements are presented of W gamma gamma and Z gamma gamma production in proton-proton collisions. Fiducial cross sections are reported based on a data sample corresponding to an integrated luminosity of 19.4 inverse femtobarns collected with the CMS detector at a center-of-mass energy of 8 TeV. Signal is identified through the W to l nu and Z to ll decay modes, where l is a muon or an electron. The production of W gamma gamma and Z gamma gamma, measured with significances of 2.6 and 5.9 standard deviations, respectively, is consistent with standard model predictions. In addition, limits on anomalous quartic gauge couplings in W gamma gamma production are determined in the context of a dimension-8 effective field theory.
Measured fiducial cross section for each channel and for the combination of channels for the WGG and ZGG analyses. The first systematic uncertainty is the combined systematic uncertainty excluding luminosity, the second is the luminosity.
Expected and observed 95% CL limits on anomalous quartic gauge couplings. Limits are obtained using WGG events in which the leading photon pT exceeds 70 GeV.
Differential cross sections for a W boson produced in association with jets are measured in a data sample of proton-proton collisions at a center-of-mass energy of 8 TeV recorded with the CMS detector and corresponding to an integrated luminosity of 19.6 inverse femtobarns. The W bosons are identified through their decay mode W to mu nu. The cross sections are reported as functions of jet multiplicity, transverse momenta, and the scalar sum of jet transverse momenta (HT) for different jet multiplicities. Distributions of the angular correlations between the jets and the muon are examined, as well as the average number of jets as a function of HT and as a function of angular variables. The measured differential cross sections are compared with tree-level and higher-order recent event generators, as well as next-to-leading-order and next-to-next-to-leading-order theoretical predictions. The agreement of the generators with the measurements builds confidence in their use for the simulation of W+jets background processes in searches for new physics at the LHC.
The cross section measurement as a function of the exclusive jet multiplicity, for jet multiplicities of up to 7.
The cross section measurement as a function of the exclusive jet multiplicity, for jet multiplicities of up to 7.
The cross section measurement as a function of the inclusive jet multiplicity, for jet multiplicities of up to 7.
The production cross section of a W boson in association with two b jets is measured using a sample of proton-proton collisions at sqrt(s) = 8 TeV collected by the CMS experiment at the CERN LHC. The data sample corresponds to an integrated luminosity of 19.8 inverse femtobarns. The W bosons are reconstructed via their leptonic decays, W to l nu, where l = mu or e. The fiducial region studied contains exactly one lepton with transverse momentum pt[l] > 30 GeV and pseudorapidity abs(eta[l]) < 2.1, with exactly two b jets with pt > 25 GeV and abs(eta) < 2.4 and no other jets with pt > 25 GeV and abs(eta) < 4.7. The cross section is measured to be sigma(pp to W (l nu)+ bb-bar) = 0.64 +/- 0.03 (stat) +/- 0.10 (syst) +/- 0.06 (theo) +/- 0.02 (lumi) pb, in agreement with standard model predictions.
Wbb production cross section in pb.
The W boson helicity fractions from top quark decays in t t-bar events are measured using data from proton-proton collisions at a centre-of-mass energy of 8 TeV. The data were collected in 2012 with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.8 inverse femtobarns. Events are reconstructed with either one muon or one electron, along with four jets in the final state, with two of the jets being identified as originating from b quarks. The measured helicity fractions from both channels are combined, yielding F[0] = 0.681 +/- 0.012 (stat) +/- 0.023 (syst), F[L] = 0.323 +/- 0.008 (stat) +/- 0.014 (syst), and F[R] = -0.004 +/- 0.005 (stat) +/- 0.014 (syst) for the longitudinal, left-, and right-handed components of the helicity, respectively. These measurements of the W boson helicity fractions are the most accurate to date and they agree with the predictions from the standard model.
Measurement of the W longitudinal (F0), left- (FL) and righ- (FR) components of the boson helicity fractions from electron+jets final states in top quark pair decays. The helicity fractions F0 and FL are measured simultaneously and are strongly anti-correlated, with statistical correlation coefficient -0.950.
Measurement of the W longitudinal (F0), left- (FL) and righ- (FR) components of the boson helicity fractions from muon+jets final states in top quark pair decays. The helicity fractions F0 and FL are measured simultaneously and are strongly anti-correlated, with statistical correlation coefficient -0.957.
Measurement of the W longitudinal (F0), left- (FL) and righ- (FR) components of the boson helicity fractions from lepton+jets final states in top quark pair decays. The helicity fractions F0 and FL are measured simultaneously and are strongly anti-correlated, with statistical correlation coefficient -0.959, and total correlation, considering both statistical and systematic uncertainties, of -0.87.
A search for exclusive or quasi-exclusive gamma gamma to W+W- production, via pp to p(*) W+W- p(*) to p(*) mu+/- e-/+ at sqrt(s) = 8 TeV, is reported using data corresponding to an integrated luminosity of 19.7 inverse femtobarns. Events are selected by requiring the presence of an electron-muon pair with large transverse momentum pt(mu+/- e-/+) > 30 GeV, and no associated charged particles detected from the same vertex. The 8 TeV results are combined with the previous 7 TeV results (obtained for 5.05 inverse femtobarns of data). In the signal region, 13 (2) events are observed over an expected background of 3.9 +/- 0.6 (0.84 +/-0.15) events for 8 (7) TeV, resulting in a combined excess of 3.4 standard deviations over the background-only hypothesis. The observed yields and kinematic distributions are compatible with the standard model prediction for exclusive and quasi-exclusive gamma gamma to W+W- production. Upper limits on the anomalous quartic gauge coupling operators a[W;0,C] (dimension-6) and f[M0,1,2,3] (dimension-8), the most stringent to date, are derived from the measured dilepton transverse momentum spectrum.
8 TeV cross section multiplied by branching fraction to opposite-sign mue final states, corrected for all experimental efficiencies and extrapolated to the full phase space.
The differential cross section and charge asymmetry for inclusive pp to W + X to mu + neutrino + X production at sqrt(s) = 8 TeV are measured as a function of muon pseudorapidity. The data sample corresponds to an integrated luminosity of 18.8 inverse femtobarns recorded with the CMS detector at the LHC. These results provide important constraints on the parton distribution functions of the proton in the range of the Bjorken scaling variable x from 10E-3 to 10E-1.
Summary of the measured differential cross section $d\sigma^{+}/d\eta$. The theoretical predictions are obtained using the FEWZ 3.1 NNLO MC tool interfaced with five different PDF sets.
Summary of the measured differential cross section $d\sigma^{-}/d\eta$. The theoretical predictions are obtained using the FEWZ 3.1 NNLO MC tool interfaced with five different PDF sets.
Summary of the measured charge asymmetry $\mathcal{A}$. The theoretical predictions are obtained using the FEWZ 3.1 NNLO MC tool interfaced with five different PDF sets.
A search for a heavy Higgs boson in the H to WW and H to ZZ decay channels is reported. The search is based upon proton-proton collision data samples corresponding to an integrated luminosity of up to 5.1 inverse femtobarns at sqrt(s) = 7 TeV and up to 19.7 inverse femtobarns at sqrt(s) = 8 TeV, recorded by the CMS experiment at the CERN LHC. Several final states of the H to WW and H to ZZ decays are analyzed. The combined upper limit at the 95% confidence level on the product of the cross section and branching fraction exclude a Higgs boson with standard model-like couplings and decays in the range 145 < m[H] < 1000 GeV. We also interpret the results in the context of an electroweak singlet extension of the standard model.
Upper limits at 95\% CL on the cross section for a heavy Higgs boson decaying to a pair of W bosons as a function of its mass and its width relative to a SM-like Higgs boson.
Upper limits at 95\% CL on the cross section for a heavy Higgs boson decaying to a pair of Z bosons as a function of its mass and its width relative to a SM-like Higgs boson.
Upper limits at 95% CL on the cross section for a heavy Higgs boson as a function of its mass and its width relative to a SM-like Higgs boson. Both, gluon-gluon fusion and VBF production processes are combined, assuming a SM-like ratio between the two.
A measurement of the W boson helicity is presented, where the W boson originates from the decay of a top quark produced in pp collisions. The event selection, optimized for reconstructing a single top quark in the final state, requires exactly one isolated lepton (muon or electron) and exactly two jets, one of which is likely to originate from the hadronization of a bottom quark. The analysis is performed using data recorded at a center-of-mass energy of 8 TeV with the CMS detector at the CERN LHC in 2012. The data sample corresponds to an integrated luminosity of 19.7 inverse femtobarns. The measured helicity fractions are F[L] = 0.298 +/- 0.028 (stat) +\- 0.032 (syst), F[0] = 0.720 +/- 0.039 (stat) +/- 0.037 (syst), and F[R] = -0.018 +/- 0.019 (stat) +/- 0.011 (syst). These results are used to set limits on the real part of the tWb anomalous couplings, gL and gR.
Measurement of the W helicity fractions using the cos(theta*l) distribution in the muon channel. The helicity fractions corresponding to the longitudinal (F0) and left-handed (FL) polarizations are extracted from the fit while FR is obtained from the constraint of FL+FR+F0 = 1. The statistical correlation between the fit parameters is about -0.90.
Measurement of the W helicity fractions using the cos(theta*l) distribution in the electron channel. The helicity fractions corresponding to the longitudinal (F0) and left-handed (FL) polarizations are extracted from the fit while FR is obtained from the constraint of FL+FR+F0 = 1. The statistical correlation between the fit parameters is about -0.90.
Measurement of the W helicity fractions using the cos(theta*l) distribution in both electron and muon channels. The helicity fractions corresponding to the longitudinal (F0) and left-handed (FL) polarizations are extracted from the combined fit while FR is obtained from the constraint of FL+FR+F0 = 1. The total correlation between the fit parameters is about -0.80.
Measurements are reported of the WZ and ZZ production cross sections in proton-proton collisions at $\sqrt{s}$ = 8 TeV in final states where one Z boson decays to b-tagged jets. The other gauge boson, either W or Z, is detected through its leptonic decay (either $W \to e\nu, \mu\nu$ or $Z \to e^+ e^-, \mu^+ \mu^-$, or $\nu\bar{\nu})$. The results are based on data corresponding to an integrated luminosity of 18.9 inverse-femtobarns collected with the CMS detector at the Large Hadron Collider. The measured cross sections, $\sigma(pp \to WZ)$ = 30.7 $\pm$ 9.3 (stat.) $\pm$ 7.1 (syst.) $\pm$ 4.1 (th.) $\pm$ 1.0 (lum.) pb and $\sigma(pp \to ZZ)$ = 6.5 $\pm$ 1.7 (stat.) $\pm$ 1.0 (syst.) $\pm$ 0.9 (th.) $\pm$ 0.2 (lum.) pb, are consistent with next-to-leading order quantum chromodynamics calculations.
The cross section for inclusive WZ production for the mass range 60 < M(Z) < 120 GeV.
The cross section for inclusive ZZ production for the mass range 60 < M(Z) < 120 GeV.
The cross section for inclusive WZ production in the region defined by 60 < M(Z) < 120 GeV and PT(W) > 100 GeV.
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