We present a measurement of the $W$ boson production charge asymmetry in $p\bar{p}\rightarrow W+X \rightarrow e\nu +X$ events at a center of mass energy of 1.96 TeV, using 9.7 fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The neutrino longitudinal momentum is determined using a neutrino weighting method, and the asymmetry is measured as a function of the $W$ boson rapidity. The measurement extends over wider electron pseudorapidity region than previous results, and is the most precise to date, allowing for precise determination of proton parton distribution functions in global fits.
${\it CP}$-folded $W$ charge asymmetry for data and predictions from MC@NLO using NNPDF2.3 PDFs tabulated in percent (%) for each $|y_W|$ bin. The $\langle|y_W|\rangle$ is calculated as the cross section weighted average of $y_W$ in each bin from RESBOS with photos. For data, the first uncertainty is statistical and the second is systematic. The uncertainties on the prediction come from both the PDF uncertainties and $\alpha_s$ uncertainties. The numbers in this table are the revised data published on 10th December 2014 (after the journal publication).
Correlation coefficients between central values of asymmetry in different $|y_W|$ bins.
First measurements of the W -> lnu and Z/gamma* -> ll (l = e, mu) production cross sections in proton-proton collisions at sqrt(s) = 7 TeV are presented using data recorded by the ATLAS experiment at the LHC. The results are based on 2250 W -> lnu and 179 Z/gamma* -> ll candidate events selected from a data set corresponding to an integrated luminosity of approximately 320 nb-1. The measured total W and Z/gamma*-boson production cross sections times the respective leptonic branching ratios for the combined electron and muon channels are $\stotW$ * BR(W -> lnu) = 9.96 +- 0.23(stat) +- 0.50(syst) +- 1.10(lumi) nb and $\stotZg$ * BR(Z/gamma* -> ll) = 0.82 +- 0.06(stat) +- 0.05(syst) +- 0.09(lumi) nb (within the invariant mass window 66 < m_ll < 116 GeV). The W/Z cross-section ratio is measured to be 11.7 +- 0.9(stat) +- 0.4(syst). In addition, measurements of the W+ and W- production cross sections and of the lepton charge asymmetry are reported. Theoretical predictions based on NNLO QCD calculations are found to agree with the measurements.
Measured fiducial cross section times leptonic branching ratio for W+ production in the W+ -> e+ nu final state.
Measured fiducial cross section times leptonic branching ratio for W- production in the W- -> e- nubar final state.
Measured fiducial cross section times leptonic branching ratio for W+/- production in the combined W+ -> e+ nu and W- -> e- nubar final state.
Dijet angular distributions from the first LHC pp collisions at center-of-mass energy sqrt(s) = 7 TeV have been measured with the ATLAS detector. The dataset used for this analysis represents an integrated luminosity of 3.1 pb-1. Dijet $\chi$ distributions and centrality ratios have been measured up to dijet masses of 2.8 TeV, and found to be in good agreement with Standard Model predictions. Analysis of the $\chi$ distributions excludes quark contact interactions with a compositeness scale $\Lambda$ below 3.4 TeV, at 95% confidence level, significantly exceeding previous limits.
CHI distribution for mass bin 340 to 520 GeV.
CHI distribution for mass bin 520 to 800 GeV.
CHI distribution for mass bin 800 to 1200 GeV.
A search for new heavy particles manifested as resonances in two-jet final states is presented. The data were produced in 7 TeV proton-proton collisions by the Large Hadron Collider (LHC) and correspond to an integrated luminosity of 315 nb^-1 collected by the ATLAS detector. No resonances were observed. Upper limits were set on the product of cross section and signal acceptance for excited-quark (q*) production as a function of q* mass. These exclude at the 95% CL the q* mass interval 0.30 < mq* < 1.26 TeV, extending the reach of previous experiments.
The dijet mass distribution (NUMBER OF EVENTS).
95 PCT CL upper limit of the cross section x acceptance.
This paper presents a search for the t-channel exchange of an R-parity violating scalar top quark (\={t}) in the emu continuum using 2.1/fb of data collected by the ATLAS detector in sqrt(s) = 7 TeV pp collisions at the Large Hadron Collider. Data are found to be consistent with the expectation from the Standard Model backgrounds. Limits on R-parity-violating couplings at 95% C.L. are calculated as a function of the scalar top mass (m_{\={t}}). The upper limits on the production cross section for pp->emuX, through the t-channel exchange of a scalar top quark, ranges from 170 fb for m_{\={t}}=95 GeV to 30 fb for m_{\={t}}=1000 GeV.
The observed E-MU invariant mass distribution plus SM background and signal predicitons for a n stop mass of 95 GeV.
Information about the signal samples used.
The ratios of the observed and expected upper cross section limits to the theoretical cross sections as a function of the scalar top mass.
Measurements are presented of the properties of high transverse momentum jets, produced in proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV. The data correspond to an integrated luminosity of 35 pb^-1 and were collected with the ATLAS detector in 2010. Jet mass, width, eccentricity, planar flow and angularity are measured for jets reconstructed using the anti-kt algorithm with distance parameters R = 0.6 and 1.0, with transverse momentum pT > 300 GeV and pseudorapidity |eta| < 2. The measurements are compared to the expectations of Monte Carlo generators that match leading-logarithmic parton showers to leading-order, or next-to-leading-order, matrix elements. The generators describe the general features of the jets, although discrepancies are observed in some distributions.
The jet mass distribution for R=0.6 jets in the full 2010 dataset corrected for pileup and corrected to the particle level.
The jet mass distribution for R=1.0 jets in the full 2010 dataset corrected for pileup and corrected to the particle level.
The jet width distribution for R=0.6 jets in the full 2010 dataset corrected for pileup and corrected to the particle level.
Results are presented of a search for new particles decaying to large numbers of jets in association with missing transverse momentum, using 4.7 fb^-1 of pp collision data at sqrt(s) = 7 TeV collected by the ATLAS experiment at the Large Hadron Collider in 2011. The event selection requires missing transverse momentum, no isolated electrons or muons, and from >=6 to >=9 jets. No evidence is found for physics beyond the Standard Model. The results are interpreted in the context of a MSUGRA/CMSSM supersymmetric model, where, for large universal scalar mass m_0, gluino masses smaller than 840 GeV are excluded at the 95% confidence level, extending previously published limits. Within a simplified model containing only a gluino octet and a neutralino, gluino masses smaller than 870 GeV are similarly excluded for neutralino masses below 100 GeV.
Distribution of the variable ETmiss/sqrt(HT) for events with >= 7 jets each having transverse momentum > 55 GeV. The table gives the number of observed data events, the expected standard model backgroud prediction and the signal expected from the SUSY signal process.
Distribution of the variable ETmiss/sqrt(HT) for events with >= 6 jets each having transverse momentum > 80 GeV. The table gives the number of observed data events, the expected standard model backgroud prediction and the signal expected from the SUSY signal process.
Distribution of the variable ETmiss/sqrt(HT) for events with >= 8 jets each having transverse momentum > 55 GeV. The table gives the number of observed data events, the expected standard model backgroud prediction and the signal expected from the SUSY signal process.
This letter reports the results of a search for top and bottom squarks from gluino pair production in 4.7 fb^-1 of pp collisions at sqrt(s) = 7 TeV using the ATLAS detector at the LHC. The search is performed in events with large missing transverse momentum and at least three jets identified as originating from a b-quark. Exclusion limits are presented for a variety of gluino-mediated models with gluino masses up to 1 TeV excluded.
Figure 2-a. Observed limit +1sigma-th.
Figure 2-a. Observed limit.
Figure 2-a. Observed limit -1sigma-th.
Distributions sensitive to the underlying event are studied in events containing one or more charged-particle jets produced in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector at the Large Hadron Collider (LHC). These measurements reflect 800 inverse microbarns of data taken during 2010. Jets are reconstructed using the antikt algorithm with radius parameter R varying between 0.2 and 1.0. Distributions of the charged-particle multiplicity, the scalar sum of the transverse momentum of charged particles, and the average charged-particle pT are measured as functions of pT^JET in regions transverse to and opposite the leading jet for 4 GeV < pT^JET < 100 GeV. In addition, the R-dependence of the mean values of these observables is studied. In the transverse region, both the multiplicity and the scalar sum of the transverse momentum at fixed pT^JET vary significantly with R, while the average charged-particle transverse momentum has a minimal dependence on R. Predictions from several Monte Carlo tunes have been compared to the data; the predictions from Pythia 6, based on tunes that have been determined using LHC data, show reasonable agreement with the data, including the dependence on R. Comparisons with other generators indicate that additional tuning of soft-QCD parameters is necessary for these generators. The measurements presented here provide a testing ground for further development of the Monte Carlo models.
Mean value of N(C=CHARGED) v jet PT for R=0.2.
Mean value of N(C=CHARGED) v jet PT for R=0.4.
Mean value of N(C=CHARGED) v jet PT for R=0.6.
The b-hadron production cross section is measured with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV, using 3.3 pb^-1 of integrated luminosity, collected during the 2010 LHC run. The b-hadrons are selected by partially reconstructing D*muX final states. Differential cross sections are measured as functions of the transverse momentum and pseudorapidity. The measured production cross section for a b-hadron with pT>9 GeV and |eta|<2.5 is 32.7 pm 0.8 (stat) ^{+4.5}_{-6.8} (syst) ub, higher than the next-to-leading-order QCD predictions but consistent within the experimental and theoretical uncertainties.
$b$ hadron $p_\perp$ at $\sqrt{s}=7$ TeV.
$b$ hadron $\eta$ at $\sqrt{s}=7$ TeV.
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