A study of dijet production in proton-proton collisions was performed at sqrt(s) = 7 TeV for jets with pt > 35 GeV and abs(y) < 4.7 using data collected with the CMS detector at the LHC in 2010. Events with at least one pair of jets are denoted as 'inclusive'. Events with exactly one pair of jets are called 'exclusive'. The ratio of the cross section of all pairwise combinations of jets to the exclusive dijet cross section as a function of the rapidity difference between jets abs(Delta(y)) is measured for the first time up to abs(Delta(y)) = 9.2. The ratio of the cross section for the pair consisting of the most forward and the most backward jet from the inclusive sample to the exclusive dijet cross section is also presented. The predictions of the Monte Carlo event generators PYTHIA6 and PYTHIA8 agree with the measurements. In both ratios the HERWIG++ generator exhibits a more pronounced rise versus abs(Delta(y)) than observed in the data. The BFKL-motivated generators CASCADE and HEJ+ARIADNE predict for these ratios a significantly stronger rise than observed.
Inclusive to exclusive dijet production ratio.
Mueller-Navelet to exclusive dijet production ratio.
A measurement of the triple-differential cross section (sigma as a function of the photon pt and eta and the jet eta) in photon + jets final states using a data sample from proton-proton collisions at sqrt(s) = 7 TeV is presented. This sample corresponds to an integrated luminosity of 2.14 inverse femtobarns collected by the CMS detector at the LHC. Photons and jets are reconstructed within a pseudorapidity range of abs(eta) < 2.5, and are required to have transverse momenta in the range 40 < pt(gamma) < 300 GeV and pt(jet) > 30 GeV, respectively. The measurements are compared to theoretical predictions from the SHERPA leading-order QCD Monte Carlo event generator and the next-to-leading-order perturbative QCD calculation from JETPHOX. The predictions are found to be consistent with the data over most of the examined kinematic region.
The triple-differential cross sections d3sig/(dp^gamma_T deta^gamma deta^jet) for photons located in the central region ,|eta(gamma)|<0.9. A 2.2 PCT luminosity uncertainty is included in the systematic uncertainty.
The triple-differential cross sections d3sig/(dp^gamma_T deta^gamma deta^jet) for photons located in the central region,|eta(gamma)|=0.9-1.44. A 2.2 PCT luminosity uncertainty is included in the systematic uncertainty.
The triple-differential cross sections d3sig/(dp_T^gamma deta^gamma deta^jet) for photons located in forward region,|eta(gamma)|=1.57-2.1. A 2.2% luminosity uncertainty is included in the systematic uncertainty.
The first measurement of the cross section ratio $\sigma_\mathrm{ t \bar{t} b \bar{b}} / \sigma_\mathrm{ t \bar{t} jj }$ is presented using a data sample corresponding to an integrated luminosity of 19.6 fb$^{-1}$ collected in pp collisions at $\sqrt{s}$ = 8 TeV with the CMS detector at the LHC. Events with two leptons ($\mathrm{e}$ or $\mu$) and four reconstructed jets, including two identified as b quark jets, in the final state are selected. The ratio is determined for a minimum jet transverse momentum $p_\mathrm{T}$ of both 20 and 40 GeV/$c$. The measured ratio is 0.022 $\pm$ 0.003 (stat) $\pm$ 0.005 (syst) for $p_\mathrm{T}$ greater than 20 GeV/$c$. The absolute cross sections $\sigma_\mathrm{ t \bar{t} b \bar{b}}$ and $\sigma_\mathrm{ t \bar{t} jj }$ are also measured. The measured ratio for $p_\mathrm{T}$ greater than 40 GeV/$c$ is compatible with a theoretical quantum chromodynamics calculation at next-to-leading order.
The number of events for each physics process and for each dilepton category after fitting to the data, their total, and the observed total number of events. The results are after the final event selection. The $Z/\gamma^* \to \ell\ell$ uncertainty is from data, while all other uncertainties include only the statistical uncertainties in the MC samples.
Summary of the systematic uncertainties from various sources contributing to $\sigma_{t\bar{t}b\bar{b}}$, $\sigma_{t\bar{t}jj}$, and the ratio $\sigma_{t\bar{t}b\bar{b}/t\bar{t}jj}$ for a jet pt threshold of $p_{\rm T}$ > 20 GeV in the visible phase space.
The measured cross sections $\sigma_{t\bar{t}b\bar{b}}$ and $\sigma_{t\bar{t}jj}$ and their ratio are given for the visible phase space (PS) defined as two leptons with $p_{\rm T}$ > 20 GeV and $|\eta|$ < 2.4 plus four jets, including two b jets with $p_{\rm T}$ > 20 GeV and $|\eta|$ < 2.5, and the full phase space, corrected for acceptance and branching fractions. The full phase-space results are given for jet thresholds of $p_{\rm T}$ > 20 and 40 GeV. The predictions of a NLO theoretical calculation for the full phase space and $p_{\rm T}$ > 40 GeV are also given.
Measurements of the inclusive jet cross section with the anti-kt clustering algorithm are presented for two radius parameters, R=0.5 and 0.7. They are based on data from LHC proton-proton collisions at $\sqrt{s}$ = 7 TeV corresponding to an integrated luminosity of 5.0 inverse femtobarns collected with the CMS detector in 2011. The ratio of these two measurements is obtained as a function of the rapidity and transverse momentum of the jets. Significant discrepancies are found comparing the data to leading-order simulations and to fixed-order calculations at next-to-leading order, corrected for nonperturbative effects, whereas simulations with next-to-leading-order matrix elements matched to parton showers describe the data best.
Inclusive Jet cross section with R = 0.5 in the rapidity bin 0 < |y| < 0.5. The total uncorrelated uncertainty includes statistical one and systematic uncorrelated. The total systematic uncertainty includes all other sources, especially the luminosity uncertainty of 2.2%. The total error can be obtained as a quadratic sum of uncorrelated and correlated one. The NP correction can be used to scale theory prediction to compare to data at particle level.
Inclusive Jet cross section with R = 0.5 in the rapidity bin 0.5 < |y| < 1. The total uncorrelated uncertainty includes statistical one and systematic uncorrelated. The total systematic uncertainty includes all other sources, especially the luminosity uncertainty of 2.2%. The total error can be obtained as a quadratic sum of uncorrelated and correlated one. The NP correction can be used to scale theory prediction to compare to data at particle level.
Inclusive Jet cross section with R = 0.5 in the rapidity bin 1 < |y| < 1.5. The total uncorrelated uncertainty includes statistical one and systematic uncorrelated. The total systematic uncertainty includes all other sources, especially the luminosity uncertainty of 2.2%. The total error can be obtained as a quadratic sum of uncorrelated and correlated one. The NP correction can be used to scale theory prediction to compare to data at particle level.
The production cross section for a W boson and two b jets is measured using proton-proton collisions at sqrt(s) = 7 TeV in a data sample collected with the CMS experiment at the LHC corresponding to an integrated luminosity of 5.0 inverse femtobarns. The W + b b-bar events are selected in the W to mu nu decay mode by requiring a muon with transverse momentum pt > 25 GeV and pseudorapidity abs(eta) < 2.1, and exactly two b-tagged jets with pt > 25 GeV and abs(eta) < 2.4. The measured W + b b-bar production cross section in the fiducial region, calculated at the level of final-state particles, is sigma(pp to W + b b-bar) x B(W to mu nu) = 0.53 +/- 0.05 (stat.) +/- 0.09 (syst.) +/- 0.06 (theo.) +/- 0.01 (lum.) pb, in agreement with the standard model prediction. In addition, kinematic distributions of the W + b b-bar system are in agreement with the predictions of a simulation using MADGRAPH and PYTHIA.
The measured $W+b\bar{b}$ cross section.
Parameters for theoretical comparison: theoretical $W+b\bar{b}$ cross section from MCFM and the two corrections (additive double parton scattering cross section estimation at the parton jet level, and multiplicative hadronization correction factor $C_{b\rightarrow B}$ ) that need to be applied in this order to it to compare to the observed cross section.
The underlying event activity in proton-proton collisions at forward pseudorapidity (-6.6 < eta < -5.2) is studied with the CMS detector at the LHC, using a novel observable: the ratio of the forward energy density, dE/d(eta), for events with a charged-particle jet produced at central pseudorapidity (abs(eta[jet]) < 2) to the forward energy density for inclusive events. This forward energy density ratio is measured as a function of the central jet transverse momentum, pt, at three different pp centre-of-mass energies (sqrt(s) = 0.9, 2.76, and 7 TeV). In addition, the sqrt(s) evolution of the forward energy density is studied in inclusive events and in events with a central jet. The results are compared to those of Monte Carlo event generators for pp collisions and are discussed in terms of the underlying event. Whereas the dependence of the forward energy density ratio on jet pt at each sqrt(s) separately can be well reproduced by some models, all models fail to simultaneously describe the increase of the forward energy density with sqrt(s) in both inclusive events and in events with a central jet.
Ratio of the energy deposited in the pseudorapidity range $-6.6 < \eta < -5.2$ for events with a charged-particle jet with $|\eta^\text{jet}| < 2$ with respect to the energy in inclusive events, as a function of the jet transverse momentum $p_{\rm T}$ for $\sqrt{s} =$ 0.9, 2.76 , and 7 TeV. Data are taken from the Rivet Analysis.
Event-shape variables, which are sensitive to perturbative and nonperturbative aspects of quantum chromodynamic (QCD) interactions, are studied in multijet events recorded in proton-proton collisions at sqrt(s) = 7 TeV. Events are selected with at least one jet with transverse momentum pt > 110 GeV and pseudorapidity abs(eta) < 2.4, in a data sample corresponding to integrated luminosities of up to 5 inverse femtobarns. The distributions of five event-shape variables in various leading jet pt ranges are compared to predictions from different QCD Monte Carlo event generators.
Transverse thrust for $110 < p_{T,1} < 170$ GeV.
Transverse thrust for $170 < p_{T,1} < 250$ GeV.
Transverse thrust for $250 < p_{T,1} < 320$ GeV.
Measurements of inclusive jet and dijet production cross sections are presented. Data from LHC proton-proton collisions at $\sqrt{s}$ = 7 TeV, corresponding to 5.0 inverse femtobarns of integrated luminosity, have been collected with the CMS detector. Jets are reconstructed up to rapidity 2.5, transverse momentum 2 TeV, and dijet invariant mass 5 TeV, using the anti-k$_t$ clustering algorithm with distance parameter R = 0.7. The measured cross sections are corrected for detector effects and compared to perturbative QCD predictions at next-to-leading order, using five sets of parton distribution functions.
Inclusive Jet Cross Section for |rapidity| < 0.5 as a function of the jet transverse momentum. The (sys) error is the total systematic error, including the luminosity uncertainty of 2.2%.
Inclusive Jet Cross Section for |rapidity| 0.5 TO 1.0 as a function of the jet transverse momentum. The (sys) error is the total systematic error, including the luminosity uncertainty of 2.2%.
Inclusive Jet Cross Section for |rapidity| 1.0 TO 1.5 as a function of the jet transverse momentum. The (sys) error is the total systematic error, including the luminosity uncertainty of 2.2%.
The normalised differential top quark-antiquark production cross section is measured as a function of the jet multiplicity in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC with the CMS detector. The measurement is performed in both the dilepton and lepton + jets decay channels using data corresponding to an integrated luminosity of 5.0 inverse femtobarns. Using a procedure to associate jets to decay products of the top quarks, the differential cross section of the t t-bar production is determined as a function of the additional jet multiplicity in the lepton + jets channel. Furthermore, the fraction of events with no additional jets is measured in the dilepton channel, as a function of the threshold on the jet transverse momentum. The measurements are compared with predictions from perturbative quantum chromodynamics and no significant deviations are observed.
Normalised differential TOP TOPBAR production cross section as a function of the jet multiplicity for jets with PT(JET) > 30 GeV in the dilepton channel. The statistical and main experimental and model systematic uncertainties are displayed.
Normalised differential TOP TOPBAR production cross section as a function of the jet multiplicity for jets with PT(JET) > 60 GeV in the dilepton channel. The statistical and main experimental and model systematic uncertainties are displayed.
Normalised differential TOP TOPBAR production cross section as a function of the jet multiplicity for jets with PT(JET) > 35 GeV in the lepton+jets channel. The statistical and main experimental and model systematic uncertainties are displayed.
A search for quark compositeness using dijet angular distributions from pp collisions at sqrt(s) = 7 TeV is presented. The search has been carried out using a data sample corresponding to an integrated luminosity of 2.2 inverse femtobarns, recorded by the CMS experiment at the LHC. Normalized dijet angular distributions have been measured for dijet invariant masses from 0.4 TeV to above 3 TeV and compared with a variety of contact interaction models, including those which take into account the effects of next-to-leading-order QCD corrections. The data are found to be in agreement with the predictions of perturbative QCD, and lower limits are obtained on the contact interaction scale, ranging from 7.5 up to 14.5 TeV at 95% confidence level.
Normalized dijet angular distributions for |yboost| < 1.11 and Mjj > 3.0 TeV.
Normalized dijet angular distributions for yboost < 1.11 and 2.4 < Mjj < 3.0 TeV.
Normalized dijet angular distributions for yboost < 1.11 and 1.9 < Mjj < 2.4 TeV.
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