We present cross section measurements for Z/gamma*+jets+X production, differential in the transverse momenta of the three leading jets. The data sample was collected with the D0 detector at the Fermilab Tevatron proton anti-proton collider at a center-of-mass energy of 1.96 TeV and corresponds to an integrated luminosity of 1 fb-1. Leading and next-to-leading order perturbative QCD predictions are compared with the measurements, and agreement is found within the theoretical and experimental uncertainties. We also make comparisons with the predictions of four event generators. Two parton-shower-based generators show significant shape and normalization differences with respect to the data. In contrast, two generators combining tree-level matrix elements with a parton shower give a reasonable description of the the shapes observed in data, but the predicted normalizations show significant differences with respect to the data, reflecting large scale uncertainties. For specific choices of scales, the normalizations for either generator can be made to agree with the measurements.
PT distribution of the first jet in events with one or more jets with additional constraints on the electrons.
PT distribution of the first jet in events with one or more jets.
PT distribution of the second jet in events with two or more jets with additional constraints on the electrons.
A measurement of the $\bjet$ production cross section is presented for events containing a $Z$ boson produced in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV, using data corresponding to an integrated luminosity of 2 fb$^{-1}$ collected by the CDF II detector at the Tevatron. $Z$ bosons are selected in the electron and muon decay modes. Jets are considered with transverse energy $E_T>20$ GeV and pseudorapidity $|\eta|<1.5$ and are identified as $\bjets$ using a secondary vertex algorithm. The ratio of the integrated $Z+\bjet$ cross section to the inclusive $Z$ production cross section is measured to be $3.32 \pm 0.53 {\rm (stat.)} \pm 0.42 {\rm (syst.)}\times 10^{-3}$. This ratio is also measured differentially in jet $E_T$, jet $\eta$, $Z$-boson transverse momentum, number of jets, and number of $\bjets$. The predictions from leading order Monte Carlo generators and next-to-leading-order QCD calculations are found to be consistent with the measurements within experimental and theoretical uncertainties.
Ratio of integrated Z0 + bjet cross section to inclusive Z0 production.
Ratio of the Z0 + bjet to Z0 cross section as a function of the bjet ET.
Ratio of the Z0 + bjet to Z0 cross section as a function of the bjet pseudorapidity.
We present a search for new particles whose decays produce two jets (dijets) using proton-antiproton collision data corresponding to an integrated luminosity of 1.13 fb-1 collected with the CDF II detector. The measured dijet mass spectrum is found to be consistent with next-to-leading-order perturbative QCD predictions, and no significant evidence of new particles is found. We set upper limits at the 95% confidence level on cross sections times the branching fraction for the production of new particles decaying into dijets with both jets having a rapidity magnitude |y| < 1. These limits are used to determine the mass exclusions for the excited quark, axigluon, flavor-universal coloron, E6 diquark, color-octet technirho, W', and Z'.
The measured dijet mass spectrum for both jets having rapidity from -1 to 1.
We present new measurements of differential cross sections for Z/gamma*(->mumu)+jet+X production in a 1 fb-1 data sample collected with the D0 detector in proton anti-proton collisions at sqrt{s}=1.96 TeV. Results include the first measurements differential in the Z/gamma* transverse momentum and rapidity, as well as new measurements differential in the leading jet transverse momentum and rapidity. Next-to-leading order perturbative QCD predictions are compared to the measurements, and reasonable agreement is observed, except in the region of low Z/gamma* transverse momentum. Predictions from two event generators based on matrix elements and parton showers, and one pure parton shower event generator are also compared to the measurements. These show significant overall normalization differences to the data and have varied success in describing the shape of the distributions.
Measured cross section as a function of the jet transverse momentum.
Measured cross section as a function of the jet rapidity.
Measured cross section as a function of the Z0 transverse momentum.
We present a measurement of the shape of the Z/gamma* boson transverse momentum (qT) distribution in ppbar -> Z/gamma* -> ee+X events at a center-of-mass energy of 1.96 TeV using 0.98 fb-1 of data collected with the D0 detector at the Fermilab Tevatron collider. The data are found to be consistent with the resummation prediction at low qT, but above the perturbative QCD calculation in the region of qT>30 GeV/c. Using events with qT<30 GeV/c, we extract the value of g2, one of the non-perturbative parameters for the resummation calculation. Data at large boson rapidity y are compared with the prediction of resummation and with alternative models that employ a resummed form factor with modifications in the small Bjorken x region of the proton wave function.
Normalized differential transverse momentum spectrum for Z0/GAMMA* events.
Correlation matrix for all rapidity Z bosons for the 12 bins used for PT < 30.
Normalized differential transverse momentum spectrum for Z0/GAMMA* events for the absolute rapidity region > 2 and PT < 30 GeV.
We present a measurement of the cross section for W-boson production in association with jets in pbarp collisions at sqrt(s)=1.96$ TeV. The analysis uses a data sample corresponding to an integrated luminosity of 320 pb^-1 collected with the CDF II detector. W bosons are identified in their electron decay channel and jets are reconstructed using a cone algorithm. For each W+>= n-jet sample ($n= 1 - 4$) we measure sigma(ppbar =>W+>=n$-jet)x BR(W => e nu) with respect to the transverse energy E_T of the n^th-highest E_T jet above 20 GeV, for a restricted W => e nu decay phase space. The cross sections, corrected for all detector effects, can be directly compared to particle level W+ jet(s) predictions. We present here comparisons to leading order and next-to-leading order predictions.
Measured ET differential cross section of the 1st jet in >= 1 JET plus W < E NU > events.
Measured ET differential cross section of the 2nd jet in >= 2 JET plus W < E NU > events.
Measured ET differential cross section of the 3rd jet in >= 3 JET plus W < E NU > events.
Inclusive jet cross sections in Z/gamma^* events, with Z/gamma^* decaying into an electron-positron pair, are measured as a function of jet transverse momentum and jet multiplicity in ppbar collisions at sqrt{s} = 1.96 TeV with the upgraded Collider Detector at Fermilab in Run II, based on an integrated luminosity of 1.7 fb^-1. The measurements cover the rapidity region | yjet | < 2.1 and the transverse momentum range ptjet > 30 GeV/c. Next-to-leading order perturbative QCD predictions are in good agreement with the measured cross sections.
Total cross section for .GE.1JET.
Total cross section for .GE.2JET.
Total cross section for .GE.3JET.
From a total data sample of 701.1 pb^-1 recorded with e+e- centre-of-mass energies of sqrt = 161-209 GeV with the OPAL detector at LEP, 11693 W-pair candidate events are selected. These data are used to obtain measurements of the W-pair production cross sections at 10 different centre-of-mass energies. The ratio of the measured cross sections to the Standard Model expectation is found to be: data/SM = 1.002 +- 0.011(stat.) +- 0.007(syst.) +- 0.005(theory), where the uncertainties are statistical, experimental systematics and theory systematics respectively. The data are used to determine the W boson branching fractions, which are found to be consistent with lepton universality of the charged current interaction. Assuming lepton universality, the branching ratio to hadrons is determined to be 67.41 +- 0.37(stat.) +- 0.23(syst.)%, from which the CKM matrix element Vcs is determined to be 0.96+-0.017(stat.)+-0.012(syst.). The differential cross section as a function of the W^- production angle is measured for the qqev and qqmv final states. The results described in this paper are consistent with the expectations from the Standard Model.
Measured cross section for the (lepton nu lepton nu) decay mode.
Measured cross section for the (quark quark lepton nu) decay mode.
Measured cross section for the (quark quark quark quark) decay mode.
Inclusive jet production (e+e- -> e+e- +jet+X) is studied in collisions of quasi-real photons radiated by the LEP beams at e+e- centre-of-mass energies sqrt see from 189 to 209 GeV. Jets are reconstructed using the kp jet algorithm. The inclusive differential cross-section is measured as a function of the jet transverse momentum, ptjet, in the range 5 <ptjet < 40 GeV for pseudo-rapidities, etaj, in the range -1.5 < etaj < 1.5. The results are compared to predictions of perturbative QCD in next-to-leading order in the strong coupling constant.
Inclusive jet cross section for the absolute jet pseudorapidity < 1.0.
Inclusive jet cross section for the absolute jet pseudorapidity < 1.5.
We present a measurement of the shape of the boson rapidity distribution for $p\bar{p}\to Z / \gamma^* \to e^+e^- + X$ events at a center-of-mass energy of 1.96 TeV. The measurement is made for events with electron-positron mass 71 < M_ee < 111 GeV and uses 0.4 $fb^{-1}$ of data collected at the Fermilab Tevatron collider with the D0 detector. This measurement significantly reduces the uncertainties on the rapidity distribution in the forward region compared with previous measurements. Predictions of NNLO QCD are found to agree well with the data over the full rapidity range.
Normalized rapidity distribution.
Details of systematic errors.
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