The production of J/psi and Upsilon mesons in pp collisions at sqrt(s) = 8 TeV is studied with the LHCb detector. The J/psi and Upsilon mesons are reconstructed in the mu+mu- decay mode and the signal yields are determined with a fit to the mu+mu- invariant mass distributions. The analysis is performed in the rapidity range 2.0<y<4.5 and transverse momentum range 0<p_T<14(15) GeV/c of the J/psi(Upsilon) mesons. The J/psi and Upsilon production cross-sections and the fraction of J/psi mesons from b-hadron decays are measured as a function of the meson p_T and y.
The total integrated cross sections for prompt J/PSI production, assuming no polarisation, and J/PSI production from b-hadron decays in the rapidity range 2.0-4.5 and transverse momentum 0-14 GeV/c;.
Differential production cross section in rapidity for prompt J/PSI mesons (assuming no polarisation) and from J/PSI from b-hadron decays.;.
The double-differential cross sections for prompt J/PSI production (assuming no polarisation) and production of J/PSI from b-hadron decays as a function of transverse momentum for the rapidity range 2.0-2.5. Also shown in the final column is the fraction (in %) of J/PSIs from the latter.
We present a comprehensive analysis of inclusive W(\to e\nu)+n-jet (n\geq 1,2,3,4) production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV at the Tevatron collider using a 3.7 fb^{-1} dataset collected by the D0 detector. Differential cross sections are presented as a function of the jet rapidities (y), lepton transverse momentum (p_T) and pseudorapidity (\eta), the scalar sum of the transverse energies of the W boson and all jets (H_T), leading dijet p_T and invariant mass, dijet rapidity separations for a variety of jet pairings for p_T-ordered and angular-ordered jets, dijet opening angle, dijet azimuthal angular separations for p_T-ordered and angular-ordered jets, and W boson transverse momentum. The mean number of jets in an event containing a W boson is measured as a function of H_T, and as a function of the rapidity separations between the two highest-p_T jets and between the most widely separated jets in rapidity. Finally, the probability for third-jet emission in events containing a W boson and at least two jets is studied by measuring the fraction of events in the inclusive W+2-jet sample that contain a third jet over a p_T threshold. The analysis employs a regularized singular value decomposition technique to accurately correct for detector effects and for the presence of backgrounds. The corrected data are compared to particle level next-to-leading order perturbative QCD predictions, predictions from all-order resummation approaches, and a variety of leading-order and matrix-element plus parton-shower event generators. Regions of the phase space where there is agreement or disagreement with the data are discussed for the different models tested.
Differential production cross-section, normalized to the measured inclusive W boson cross-section, as a function of leading jet rapidity for events with one or more jets produced in association with a W boson. First uncertainty is statistical, second uncertainty is systematic.
Differential production cross-section, normalized to the measured inclusive W boson cross-section, as a function of second jet rapidity for events with two or more jets produced in association with a W boson. First uncertainty is statistical, second uncertainty is systematic.
Differential production cross-section, normalized to the measured inclusive W boson cross-section, as a function of third jet rapidity for events with three or more jets produced in association with a W boson. First uncertainty is statistical, second uncertainty is systematic.
This article reports a measurement of the production cross section of prompt isolated photon pairs in proton-antiproton collisions at \sqrt{s} = 1.96 TeV using the CDF II detector at the Fermilab Tevatron collider. The data correspond to an integrated luminosity of 5.36/fb. The cross section is presented as a function of kinematic variables sensitive to the reaction mechanisms. The results are compared with three perturbative QCD calculations: (1) a leading order parton shower Monte Carlo, (2) a fixed next-to-leading order calculation and (3) a next-to-leading order/next-to-next-to-leading-log resummed calculation. The comparisons show that, within their known limitations, all calculations predict the main features of the data, but no calculation adequately describes all aspects of the data.
Diphoton production cross section as a function of the diphoton invariant mass.
Diphoton production cross section as a function of the diphoton transverse momentum.
Diphoton production cross section as a function of the azimuthal angle difference in the two photons.
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.
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 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 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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Inclusive charged particle distribution as a function of XP.
Inclusive charged particle distribution as a function of rapidity (YRAP).
Inclusive charged particle distribution as a function of PT in the event plane.
Measurements of the inclusive cross-sections forK0 and Λ production in hadronic decays of the Z are presented together with measurements of two-particle correlations within pairs of Λ andK0. The results are compared with predictions from the hadronization models Jetset, based on string fragmentation, and Herwig, based on cluster decays. TheK0 spectrum is found to be harder than predicted by both models, while the Λ spectrum is softer than predicted. The correlation measurements are all reproduced well by Jetset, while Herwig misses some of the qualitative features and overestimates the size of the\(\Lambda \bar \Lambda \) correlation. Finally, the possibility of Bose-Einstein correlation in theKS0KS0 system is discussed.
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