A search is presented for extra spatial dimensions, quantum black holes, and quark contact interactions in measurements of dijet angular distributions in proton-proton collisions at sqrt(s) = 13 TeV. The data were collected with the CMS detector at the LHC and correspond to an integrated luminosity of 2.6 inverse femtobarns. The distributions are found to be in agreement with predictions from perturbative quantum chromodynamics that include electroweak corrections. Limits for different contact interaction models are obtained in a benchmark model, valid to next-to-leading order in QCD, in which only left-handed quarks participate, quark contact interactions are excluded up to a scale of 11.5 or 14.7 TeV for destructive or constructive interference, respectively. The production of quantum black holes is excluded for masses below 7.8 or 5.3 TeV, depending on the model. The lower limits for the scales of virtual graviton exchange in the Arkani-Hamed--Dimopoulos--Dvali model of extra spatial dimensions are in the range 7.9-11.2 TeV, and are the most stringent set of limits available.
Normalized dijet angular distribution for events with dijet mass > 4.8 TeV.
Normalized dijet angular distribution for events with 4.2 < dijet mass < 4.8 TeV.
Normalized dijet angular distribution for events with 3.6 < dijet mass < 4.2 TeV.
We report the first measurement of the longitudinal double-spin asymmetry $A_{LL}$ for mid-rapidity di-jet production in polarized $pp$ collisions at a center-of-mass energy of $\sqrt{s} = 200$ GeV. The di-jet cross section was measured and is shown to be consistent with next-to-leading order (NLO) perturbative QCD predictions. $A_{LL}$ results are presented for two distinct topologies, defined by the jet pseudorapidities, and are compared to predictions from several recent NLO global analyses. The measured asymmetries, the first such correlation measurements, support those analyses that find positive gluon polarization at the level of roughly 0.2 over the region of Bjorken-$x > 0.05$.
Data simulation comparison (with arbitrary normalization). Di-jet invariant mass.
Data simulation comparison (with arbitrary normalization). Difference between jet pseudorapidities.
Data simulation comparison (with arbitrary normalization). Difference between jet azimuthal angles.
A search is presented for narrow heavy resonances X decaying into pairs of Higgs bosons (H) in proton-proton collisions collected by the CMS experiment at the LHC at sqrt(s) = 8 TeV. The data correspond to an integrated luminosity of 19.7 inverse femtobarns. The search considers HH resonances with masses between 1 and 3 TeV, having final states of two b quark pairs. Each Higgs boson is produced with large momentum, and the hadronization products of the pair of b quarks can usually be reconstructed as single large jets. The background from multijet and t t-bar events is significantly reduced by applying requirements related to the flavor of the jet, its mass, and its substructure. The signal would be identified as a peak on top of the dijet invariant mass spectrum of the remaining background events. No evidence is observed for such a signal. Upper limits obtained at 95% confidence level for the product of the production cross section and branching fraction sigma(gg to X) B(X to HH to b b-bar b b-bar) range from 10 to 1.5 fb for the mass of X from 1.15 to 2.0 TeV, significantly extending previous searches. For a warped extra dimension theory with a mass scale Lambda[R] = 1 TeV, the data exclude radion scalar masses between 1.15 and 1.55 TeV.
Observed $m_\mathrm{jj}$ spectrum (black points) compared with a background estimate (black line), obtained in background only hypothesis, for HPHP category. The simulated radion resonances of $m_\mathrm{X} = 1.5$ and 2 TeV are also shown.
Observed $m_\mathrm{jj}$ spectrum (black points) compared with a background estimate (black line), obtained in background only hypothesis, for HPLP category. The simulated radion resonances of $m_\mathrm{X} = 1.5$ and 2 TeV are also shown.
Observed $m_\mathrm{jj}$ spectrum (black points) compared with a background estimate (black line), obtained in background only hypothesis, for LPHP category. The simulated radion resonances of $m_\mathrm{X} = 1.5$ and 2 TeV are also shown.
A search for new phenomena in LHC proton-proton collisions at a center-of-mass energy of $\sqrt{s}=8$ TeV was performed with the ATLAS detector using an integrated luminosity of 17.3 fb$^{-1}$. The angular distributions are studied in events with at least two jets; the highest dijet mass observed is 5.5 TeV. All angular distributions are consistent with the predictions of the Standard Model. In a benchmark model of quark contact interactions, a compositeness scale below 8.1 TeV in a destructive interference scenario and 12.0 TeV in a constructive interference scenario is excluded at 95 % CL; median expected limits are 8.9 TeV for the destructive interference scenario and 14.1 TeV for the constructive interference scenario.
mjj region 600 - 800 GeV. The observed systematic is the experimental uncertainty, while the SM prediction systematic is the theoretical uncertainty.
mjj region 800 - 1200 GeV. The observed systematic is the experimental uncertainty, while the SM prediction systematic is the theoretical uncertainty.
mjj region 1200 - 1600 GeV. The observed systematic is the experimental uncertainty, while the SM prediction systematic is the theoretical uncertainty.
A search is presented for quark contact interactions and extra spatial dimensions in proton-proton collisions at sqrt(s) = 8 TeV using dijet angular distributions. The search is based on a data set corresponding to an integrated luminosity of 19.7 inverse femtobarns collected by the CMS detector at the CERN LHC. Dijet angular distributions are found to be in agreement with the perturbative QCD predictions that include electroweak corrections. Limits on the contact interaction scale from a variety of models at next-to-leading order in QCD corrections are obtained. A benchmark model in which only left-handed quarks participate is excluded up to a scale of 9.0 (11.7) TeV for destructive (constructive) interference at 95% confidence level. Lower limits between 5.9 and 8.4 TeV on the scale of virtual graviton exchange are extracted for the Arkani-Hamed--Dimopoulos--Dvali model of extra spatial dimensions.
Measured dijet angular distributions in bin of dijet invariant mass. P=3 and P=4 refers to the two jets in the final state.
Measured dijet angular distributions in bin of dijet invariant mass.P=3 and P=4 refers to the two jets in the final state.
Measured dijet angular distributions in bin of dijet invariant mass. P=3 and P=4 refers to the two jets in the final state.
Additional jet activity in dijet events is measured using $pp$ collisions at ATLAS at a centre-of-mass energy of 7 TeV, for jets reconstructed using the anti-kt algorithm with radius parameter R=0.6. This is done using variables such as the fraction of dijet events without an additional jet in the rapidity interval bounded by the dijet subsystem and correlations between the azimuthal angles of the dijets. They are presented, both with and without a veto on additional jet activity in the rapidity interval, as a function of the mean transverse momentum of the dijets and of the rapidity interval size. The double differential dijet cross section is also measured as a function of the interval size and the azimuthal angle between the dijets. These variables probe differences in the approach to resummation of large logarithms when performing QCD calculations. The data are compared to POWHEG, interfaced to the PYTHIA 8 and HERWIG parton shower generators, as well as to HEJ with and without interfacing it to the ARIADNE parton shower generator. None of the theoretical predictions agree with the data across the full phase-space considered; however, POWHEG+PYTHIA 8 and HEJ+ARIADNE are found to provide the best agreement with the data.These measurements use the full data sample collected with the ATLAS detector in 7 TeV $pp$ collisions at the LHC and correspond to integrated luminosities of 36.1 pb$^-1$ and 4.5 fb$^-1$ for data collected during 2010 and 2011 respectively.
Gap fraction as a function of leading dijet rapidity separation.
Gap fraction as a function of leading dijet scalar mean pT in GeV.
Mean number of jets in rapidity interval as a function of leading dijet rapidity separation.
Distributions sensitive to the underlying event in QCD jet events have been measured with the ATLAS detector at the LHC, based on 37/pb of proton-proton collision data collected at a centre-of-mass energy of 7 TeV. Charged-particle mean $p_T$ and densities of all-particle $E_T$ and charged-particle multiplicity and $p_T$ have been measured in regions azimuthally transverse to the hardest jet in each event. These are presented both as one-dimensional distributions and with their mean values as functions of the leading-jet transverse momentum from 20 GeV to 800 GeV. The correlation of charged-particle mean $p_T$ with charged-particle multiplicity is also studied, and the $E_T$ densities include the forward rapidity region; these features provide extra data constraints for Monte Carlo modelling of colour reconnection and beam-remnant effects respectively. For the first time, underlying event observables have been computed separately for inclusive jet and exclusive dijet event selections, allowing more detailed study of the interplay of multiple partonic scattering and QCD radiation contributions to the underlying event. Comparisons to the predictions of different Monte Carlo models show a need for further model tuning, but the standard approach is found to generally reproduce the features of the underlying event in both types of event selection.
Transverse $\langle \sum p_T^\text{ch} / \delta\eta\,\delta\phi \rangle$ vs. $p_T^\text{lead}$ in $|\eta| < 2.5$ in incl jet / excl dijet events.
Trans-max $\langle \sum p_T^\text{ch} / \delta\eta\,\delta\phi \rangle$ vs. $p_T^\text{lead}$ in $|\eta| < 2.5$ in incl jet / excl dijet events.
Trans-min $\langle \sum p_T^\text{ch} / \delta\eta\,\delta\phi \rangle$ vs. $p_T^\text{lead}$ in $|\eta| < 2.5$ in incl jet / excl dijet events.
Double-differential dijet cross sections measured in pp collisions at the LHC with a 7 TeV centre-of-mass energy are presented as functions of dijet mass and rapidity separation of the two highest-pT jets. These measurements are obtained using data corresponding to an integrated luminosity of 4.5/fb, recorded by the ATLAS detector in 2011. The data are corrected for detector effects so that cross sections are presented at the particle level. Cross sections are measured up to 5 TeV dijet mass using jets reconstructed with the anti-kt algorithm for values of the jet radius parameter of 0.4 and 0.6. The cross sections are compared with next-to-leading-order perturbative QCD calculations by NLOJET++ corrected to account for non-perturbative effects. Comparisons with POWHEG predictions, using a next-to-leading-order matrix element calculation interfaced to a parton-shower Monte Carlo simulation, are also shown. Electroweak effects are accounted for in both cases. The quantitative comparison of data and theoretical predictions obtained using various parameterizations of the parton distribution functions is performed using a frequentist method. An example setting a lower limit on the compositeness scale for a model of contact interactions is presented, showing that the unfolded results can be used to constrain contributions to dijet production beyond that predicted by the Standard Model.
Measured double-differential dijet cross sections for the range 0.0 <= y* < 0.5 and jet radius parameter R = 0.4. The statistical uncertainties from data and MC simulation have been combined. The three columns correspond to nominal, stronger or weaker correlations between jet energy scale uncertainty components.
Measured double-differential dijet cross sections for the range 0.5 <= y* < 1.0 and jet radius parameter R = 0.4. The statistical uncertainties from data and MC simulation have been combined. The three columns correspond to nominal, stronger or weaker correlations between jet energy scale uncertainty components.
Measured double-differential dijet cross sections for the range 1.0 <= y* < 1.5 and jet radius parameter R = 0.4. The statistical uncertainties from data and MC simulation have been combined. The three columns correspond to nominal, stronger or weaker correlations between jet energy scale uncertainty components.
Invariant mass spectra for jets reconstructed using the anti-kt and Cambridge-Aachen algorithms are studied for different jet "grooming" techniques in data corresponding to an integrated luminosity of 5 inverse femtobarns, recorded with the CMS detector in proton-proton collisions at the LHC at a center-of-mass energy of 7 TeV. Leading-order QCD predictions for inclusive dijet and W/Z+jet production combined with parton-shower Monte Carlo models are found to agree overall with the data, and the agreement improves with the implementation of jet grooming methods used to distinguish merged jets of large transverse momentum from softer QCD gluon radiation.
The unfolded distributions (x1000) for the mean mass of the two leading jets in in dijet events for reconstructed AK7 jets, for the mean PT of the two leading jets in the range 220-300 GeV/c.
The unfolded distributions (x1000) for the mean mass of the two leading jets in in dijet events for reconstructed AK7 jets, for the mean PT of the two leading jets in the range 300-450 GeV/c.
The unfolded distributions (x1000) for the mean mass of the two leading jets in in dijet events for reconstructed AK7 jets, for the mean PT of the two leading jets in the range 450-500 GeV/c.
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%.
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