We present the first measurement of dijet angular distributions in ppbar collisions at sqrt{s}=1.96TeV at the Fermilab Tevatron Collider. The measurement is based on a dataset corresponding to an integrated luminosity of up to 0.7fb-1 collected with the D0 detector. Dijet angular distributions have been measured over a range of dijet masses, from 0.25TeV to above 1.1TeV. The data are in good agreement with the predictions of perturbative QCD and are used to constrain new physics models including quark compositeness, large extra dimensions, and TeV-1 scale extra dimensions. For all models we set the most stringent direct limits to date.
Normalized differential distribution in CHI(dijet) for two-jet mass 250 to 300 GeV and the non perturbative correction factor.
Normalized differential distribution in CHI(dijet) for two-jet mass 300 to 400 GeV and the non perturbative correction factor.
Normalized differential distribution in CHI(dijet) for two-jet mass 400 to 500 GeV and the non perturbative correction factor.
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.
The inclusive dijet production double differential cross section as a function of the dijet invariant mass and of the largest absolute rapidity of the two jets with the largest transverse momentum in an event is measured in proton anti-proton collisions at sqrt{s} = 1.96 TeV using 0.7 fb^{-1} integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The measurement is performed in six rapidity regions up to a maximum rapidity of 2.4. Next-to-leading order perturbative QCD predictions are found to be in agreement with the data.
Dijet double differential cross section for the absolute rapidity region 0.0 to 0.4.
Dijet double differential cross section for the absolute rapidity region 0.4 to 0.8.
Dijet double differential cross section for the absolute rapidity region 0.8 to 1.2.
We present measurements of the differential cross section dsigma/dpT_gamma for the inclusive production of a photon in association with a b-quark jet for photons with rapidities |y_gamma|< 1.0 and 30<pT_gamma <300 GeV, as well as for photons with 1.5<|y_gamma|< 2.5 and 30< pT_gamma <200 GeV, where pT_gamma is the photon transverse momentum. The b-quark jets are required to have pT>15 GeV and rapidity |y_jet| < 1.5. The results are based on data corresponding to an integrated luminosity of 8.7 fb^-1, recorded with the D0 detector at the Fermilab Tevatron $p\bar{p}$ Collider at sqrt(s)=1.96 TeV. The measured cross sections are compared with next-to-leading order perturbative QCD calculations using different sets of parton distribution functions as well as to predictions based on the kT-factorization QCD approach, and those from the Sherpa and Pythia Monte Carlo event generators.
The differential cross section as a function of PT for the production of GAMMA + B-JET in the photon |rapidity/ region < 1.0.
The differential cross section as a function of PT for the production of GAMMA + B-JET in the photon |rapidity| region 1.5-2.5.
First measurements of the differential cross sections for the inclusive production of a photon in association with a heavy quark (c, b) jet are presented, covering photon transverse momenta 30-150 GeV, photon rapidities | y_gamma| < 1.0, jet rapidities |y_jet| < 0.8, and jet transverse momenta pT_jet > 15 GeV. The results are based on an integrated luminosity of 1 fb^-1 in ppbar collisions at sqrt(s)=1.96 TeV recorded with the D0 detector at the Fermilab Tevatron Collider. The results are compared with next-to-leading order perturbative QCD predictions.
Differential cross section for (GAMMA BJET X) production in the region YRAP(GAMMA)*YRAP(JET) > 0.
Differential cross section for (GAMMA BJET X) production in the region YRAP(GAMMA)*YRAP(JET) < 0.
Differential cross section for (GAMMA CJET X) production in the region YRAP(GAMMA)*YRAP(JET) > 0.
We present a measurement of the fraction of inclusive $W$+jets events produced with net charm quantum number $\pm1$, denoted $W$+$c$-jet, in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV using approximately 1~fb$^{-1}$ of data collected by the D0 detector at the Fermilab Tevatron Collider. We identify the $W$+jets events via the leptonic $W$ boson decays. Candidate $W$+$c$-jet events are selected by requiring a jet containing a muon in association with a reconstructed $W$ boson and exploiting the charge correlation between this muon and $W$ boson decay lepton to perform a nearly model-independent background subtraction. We measure the fraction of $W$+$c$-jet events in the inclusive $W$+jets sample for jet $p_{T}>20$ GeV and pseudorapidity $|\eta|<2.5$ to be 0.074$\pm0.019$(stat.)$\pm^{0.012}_{0.014}$(syst.), in agreement with theoretical predictions. The probability that background fluctuations could produce the observed fraction of $W$+$c$-jet events is estimated to be $2.5\times 10^{-4}$, which corresponds to a 3.5 $\sigma$ statistical significance.
Measured value of the W+ charm jet to W+ jet cross sections for W decay into the (E NU) channel for various jet PT ranges.
Measured value of the W+ charm jet to W+ jet cross sections for W decay into the (MU NU) channel for various jet PT ranges.
Measured value of the W+ charm jet to W+ jet cross sections for W decay into the (LEPTON NU) channel for various jet PT ranges.
We study the process of associated photon and jet production, p+pbar --> photon + jet + X, using 8.7 fb^-1 of integrated luminosity collected by the D0 detector at the Fermilab Tevatron Collider at a center-of-mass energy sqrt{s}=1.96 TeV. Photons are reconstructed with rapidity |y^gamma| <1.0 or 1.5<|y^{gamma}| < 2.5 and transverse momentum pT^gamma GeV. The highest-p_T jet is required to be in one of four rapidity regions up to |y^{jet}|< 3.2. For each rapidity configuration we measure the differential cross sections in pT_gamma separately for events with the same sign (y^{gamma} y^{jet}}>0) and opposite sign (y^{gamma} y^{jet}<=0) of photon and jet rapidities. We compare the measured triple differential cross sections, d^3 sigma / d pT_gamma y^{gamma} y^{jet}, to next-to-leading order (NLO) perturbative QCD calculations using different sets of parton distribution functions and to predictions from the SHERPA and PYTHIA Monte Carlo event generators. The NLO calculations are found to be in general agreement with the data, but do not describe all kinematic regions.
The triple differential GAMMA+JET cross section for |y_gamma| < 1.0, |y_jet| <= 0.8 and y_gamma*y_jet > 0 A common 6.8% nomalization is included in the (sys) error.
The triple differential GAMMA+JET cross section for |y_gamma| < 1.0, |y_jet| 0.8 TO 1.6 and y_gamma*y_jet > 0 A common 6.8% nomalization is included in the (sys) error.
The triple differential GAMMA+JET cross section for |y_gamma| < 1.0, |y_jet| 1.6 TO 2.4 and y_gamma*y_jet > 0 A common 6.8% nomalization is included in the (sys) error.
We present the first model-independent measurement of the helicity of $W$ bosons produced in top quark decays, based on a 1 fb$^{-1}$ sample of candidate $t\bar{t}$ events in the dilepton and lepton plus jets channels collected by the D0 detector at the Fermilab Tevatron $p\bar{p}$ Collider. We reconstruct the angle $\theta^*$ between the momenta of the down-type fermion and the top quark in the $W$ boson rest frame for each top quark decay. A fit of the resulting \costheta distribution finds that the fraction of longitudinal $W$ bosons $f_0 = 0.425 \pm 0.166 \hbox{(stat.)} \pm 0.102 \hbox{(syst.)}$ and the fraction of right-handed $W$ bosons $f_+ = 0.119 \pm 0.090 \hbox{(stat.)} \pm 0.053 \hbox{(syst.)}$, which is consistent at the 30% C.L. with the standard model.
COS(THETA*) distribution for leptonic W decay in lepton+jets events.. Data are read from plots and errors are statistcial (sqrt(N)).
COS(THETA*) distribution for hadronic W decay in lepton+jets events.. Data are read from plots and errors are statistcial (sqrt(N)).
COS(THETA*) distribution for W decay in dilepton events.. Data are read from plots and errors are statistcial (sqrt(N)).
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 the first measurements at a hadron collider of differential cross sections for Z+jet+X production in delta phi(Z, jet), |delta y(Z, jet)| and |y_boost(Z, jet)|. Vector boson production in association with jets is an excellent probe of QCD and constitutes the main background to many small cross section processes, such as associated Higgs production. These measurements are crucial tests of the predictions of perturbative QCD and current event generators, which have varied success in describing the data. Using these measurements as inputs in tuning event generators will increase the experimental sensitivity to rare signals.
Differential cross section in bins of PHI(P=3)-PHI(P=4) for Z/GAMMA* transverse momentum > 25 GeV.
Differential cross section in bins of PHI(P=3)-PHI(P=4) for Z/GAMMA* transverse momentum > 45 GeV.
Differential cross section in bins of ABS(YRAP(P=3)-YRAP(P=4)) for Z/GAMMA* transverse momentum > 25 GeV.
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