The $W$ boson angular distribution in events with high transverse momentum jets is measured using data collected by the ATLAS experiment from proton-proton collisions at a centre-of-mass energy $\sqrt{s}=$ 8 TeV at the Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb$^{-1}$. The focus is on the contributions to $W$ + jets processes from real $W$ emission, which is achieved by studying events where a muon is observed close to a high transverse momentum jet. At small angular separations, these contributions are expected to be large. Various theoretical models of this process are compared to the data in terms of the absolute cross-section and the angular distributions of the muon from the leptonic $W$ decay.
Measured integrated cross-sections as a function of leading jet transverse momentum for the collinear region ($0.2 < \Delta R < 2.4$), the back-to-back region ($\Delta R > 2.4$) and inclusively.
Measured cross-section as a function of angular separation between the muon and the closest jet. Multiplicative correction factors for using prompt muons and prompt dressing photons in the particle-level selection, derived from ALPGEN 2.14 interfaced with PYTHIA 6.426, are also shown.
Breakdown of uncertainties in percent.
The WZ production cross section is measured by the CMS experiment at the CERN LHC in proton-proton collision data samples corresponding to integrated luminosities of 4.9 inverse femtobarns collected at sqrt(s)= 7 TeV, and 19.6 inverse femtobarns at sqrt(s)= 8 TeV. The measurements are performed using the fully-leptonic WZ decay modes with electrons and muons in the final state. The measured cross sections for 71 < m[Z] < 111 GeV are sigma(pp to WZ; sqrt(s)= 7 TeV) = 20.14 +/- 1.32 (stat) +/- 1.13 (syst) +/- 0.44 (lumi) pb and sigma(pp to WZ; sqrt(s)= 8 TeV) = 24.09 +/- 0.87 (stat) +/- 1.62 (syst) +/- 0.63 (lumi) pb. Differential cross sections with respect to the Z boson pt, the leading jet pt, and the number of jets are obtained using the sqrt(s)= 8 TeV data. The results are consistent with standard model predictions and constraints on anomalous triple gauge couplings are obtained.
The measured WZ cross section for 71 < mZ < 111 GeV using 7 TeV data. The theory uncertainty only includes QCD scales variations.
The measured WZ cross section for 71 < mZ < 111 GeV using 8 TeV data. The theory uncertainty only includes QCD scales variations.
Differential cross section as function of the Z boson transverse momentum.
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.
A first measurement of the top quark mass using the decay channel t to (W to l nu) (b to J/psi + X to mu+ mu- + X) is presented. The analysis uses events selected from the proton-proton collisions recorded with the CMS detector at the LHC at a center-of-mass energy of 8 TeV. The data correspond to an integrated luminosity of 19.7 inverse femtobarns, with 666 t t-bar and single top quark candidate events containing a reconstructed J/psi candidate decaying into an oppositely-charged muon pair. The mass of the (J/psi + l) system, where l is an electron or a muon from W boson decay, is used to extract a top quark mass of 173.5 +/- 3.0 (stat) +/- 0.9 (syst) GeV.
Number of selected events from simulations and observed in data. The uncertainties are statistical.
Summary of the impact of systematic uncertainties on the top quark mass according to the contributions from each source.
Measurements of normalized differential cross-sections of top quark pair ($t\bar t$) production are presented as a function of the mass, the transverse momentum and the rapidity of the $t\bar t$ system in proton-proton collisions at center-of-mass energies of $\sqrt{s}$ = 7 TeV and 8 TeV. The dataset corresponds to an integrated luminosity of 4.6 fb$^{-1}$ at 7 TeV and 20.2 fb$^{-1}$ at 8 TeV, recorded with the ATLAS detector at the Large Hadron Collider. Events with top quark pair signatures are selected in the dilepton final state, requiring exactly two charged leptons and at least two jets with at least one of the jets identified as likely to contain a $b$-hadron. The measured distributions are corrected for detector effects and selection efficiency to cross-sections at the parton level. The differential cross-sections are compared with different Monte Carlo generators and theoretical calculations of $t\bar t$ production. The results are consistent with the majority of predictions in a wide kinematic range.
Parton-level normalized $t\bar t$ differential cross-sections for $t\bar t$ system mass $m_{t\bar t}$ at $\sqrt{s}$ = 7 TeV. The cross-sections in the last bins include events (if any) beyond of the bin edges. The uncertainties quoted in the second column represent the statistical and systematic uncertainties added in quadrature.
Parton-level normalized $t\bar t$ differential cross-sections for the $t\bar t$ system transverse momentum $p_{T, t\bar t}$ at $\sqrt{s}$ = 7 TeV. The cross-sections in the last bins include events (if any) beyond of the bin edges. The uncertainties quoted in the second column represent the statistical and systematic uncertainties added in quadrature.
Parton-level normalized $t\bar t$ differential cross-sections for the $t\bar t$ system absolute rapidity $|y_{t\bar t}|$ at $\sqrt{s}$ = 7 TeV. The cross-sections in the last bins include events (if any) beyond of the bin edges. The uncertainties quoted in the second column represent the statistical and systematic uncertainties added in quadrature.
A measurement is presented of the cross section for the electroweak production of a W boson in association with two jets in proton-proton collisions at a center-of-mass energy of 8 TeV. The data set was collected with the CMS detector and corresponds to an integrated luminosity of 19.3 inverse femtobarns. The measured fiducial cross section for W bosons decaying to electrons or muons and for pT(j1) > 60 GeV, pT(j2) > 50 GeV, |eta(j)| < 4.7, and m(jj) > 1000 GeV is 0.42 +/- 0.04 (stat) +/- 0.09 (syst) +/- 0.01 (lumi) pb. This result is consistent with the standard model leading-order prediction of 0.50 +/- 0.02 (scale) +/- 0.02 (PDF) pb obtained with MADGRAPH5_aMC@NLO 2.1 interfaced to PYTHIA 6.4. This is the first cross section measurement for this process.
The measured values for the EW W(-->env, munv)+2-jets fiducial cross section.
Measurements are reported of the normalized differential cross sections for top quark pair production with respect to four kinematic event variables: the missing transverse energy; the scalar sum of the jet transverse momentum (pT); the scalar sum of the pT of all objects in the event; and the pT of leptonically decaying W bosons from top quark decays. The data sample, collected using the CMS detector at the LHC, consists of 5.0 inverse femtobarns of proton-proton collisions at sqrt(s) = 7 TeV and 19.7 inverse femtobarns at sqrt(s) = 8 TeV. Top quark pair events containing one electron or muon are selected. The results are presented after correcting for detector effects to allow direct comparison with theoretical predictions. No significant deviations from the predictions of several standard model event simulation generators are observed.
Normalized $t\bar{t}$ differential cross section measurements with respect to the $E^{miss}_{T}$ variable at a center-of-mass energy of 7 TeV (combination of electron and muon channels).
Normalized $t\bar{t}$ differential cross section measurements with respect to the $H_T$ variable at a center-of-mass energy of 7 TeV (combination of electron and muon channels).
Normalized $t\bar{t}$ differential cross section measurements with respect to the $S_T$ variable at a center-of-mass energy of 7 TeV (combination of electron and muon channels).
This paper presents a measurement of the double-differential cross section for the Drell-Yan $Z/\gamma^{*} \rightarrow \ell^{+} \ell^{-}$ and photon-induced $\gamma\gamma \rightarrow \ell^{+} \ell^{-}$ processes where $\ell$ is an electron or muon. The measurement is performed for invariant masses of the lepton pairs, $m_{\ell\ell}$, between 116 GeV and 1500 GeV, using a sample of 20.3 fb$^{-1}$ of pp collisions data at centre-of-mass energy of $\sqrt{s}$ = 8 TeV collected by the ATLAS detector at the LHC in 2012. The data are presented double differentially in invariant mass and absolute dilepton rapidity as well as in invariant mass and absolute pseudorapidity separation of the lepton pair. The single-differential cross section as a function of $m_{\ell\ell}$ is also reported. The electron and muon channel measurements are combined and a total experimental precision of better than 1% is achieved at low $m_{\ell\ell}$. A comparison to next-to-next-to-leading order perturbative QCD predictions using several recent parton distribution functions and including next-to-leading order electroweak effects indicates the potential of the data to constrain parton distribution functions. In particular, a large impact of the data on the photon PDF is demonstrated.
The combined Born-level single-differential cross section as a function of invariant mass. The measurements are listed together with the statistical and systematic uncertainties. The systematic uncertainties are separated into one uncorrelated, 35 correlated sources and the luminosity uncertainty. The sign of the uncertainty corresponds to a one standard deviation upward shift of the uncertainty source, where +/- means "+" and -/+ means "-".
The combined Born-level double-differential cross section as a function of invariant mass and absolute rapidity. The measurements are listed together with the statistical and systematic uncertainties. The systematic uncertainties are separated into one uncorrelated, 35 correlated sources and the luminosity uncertainty. The sign of the uncertainty corresponds to a one standard deviation upward shift of the uncertainty source, where +/- means "+" and -/+ means "-".
The combined Born-level double-differential cross section as a function of invariant mass and absolute pseudorapidity separation of the leptons. The measurements are listed together with the statistical and systematic uncertainties. The systematic uncertainties are separated into one uncorrelated, 35 correlated sources and the luminosity uncertainty. The sign of the uncertainty corresponds to a one standard deviation upward shift of the uncertainty source, where +/- means "+" and -/+ means "-".
The cross section for Higgs boson production in pp collisions is studied using the H to WW decay mode, followed by leptonic decays of the W bosons to an oppositely charged electron-muon pair in the final state. The measurements are performed using data collected by the CMS experiment at the LHC at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.4 inverse femtobarns. The Higgs boson transverse momentum (pT) is reconstructed using the lepton pair pT and missing pT. The differential cross section times branching fraction is measured as a function of the Higgs boson pT in a fiducial phase space defined to match the experimental acceptance in terms of the lepton kinematics and event topology. The production cross section times branching fraction in the fiducial phase space is measured to be 39 +/- 8 (stat) +/- 9 (syst) fb. The measurements are found to agree, within experimental uncertainties, with theoretical calculations based on the standard model.
The fiducial differential cross section in each Higgs pT bin. The first uncertainty is the total (stat+syst) uncertainty. The second is the statistical uncertainty and the third and fourth are Type A and Type B systematic uncertainties, respectively. The last one is the model dependence uncertainty (Type C).
The measured total cross section in the fiducial region. The first systematic uncertainty is the statistical uncertainty and the second is the systematic.
Correlation matrix among the Higgs pT bins of the differential spectrum.
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.
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