1,004 research outputs found

    Measurement of triple differential photon plus jet cross section by D0

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    We report on a new measurement of triple differential cross section for the process ppbar -> photon + jet + X in ppbar collisions at sqrt(s)=1.96 TeV by the D0 Collaboration at Fermilab based on a dataset corresponding to an integrated luminosity of 1.1 fb-1.Comment: 3 pages, 1 figure, To appear in the Proceedings of the 2007 Europhysics Conference on High Energy Physics, Manchester, UK. Accepted for publication in Journal of Physics : Conference Serie

    Next-To-Leading Order Determination of Fragmentation Functions

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    We analyse LEP and PETRA data on single inclusive charged hadron cross-sections to establish new sets of Next-to-Leading order Fragmentation Functions. Data on hadro-production of large-p⊥p_{\bot} hadrons are also used to constrain the gluon Fragmentation Function. We carry out a critical comparison with other NLO parametrizations

    Generalizing the DGLAP Evolution of Fragmentation Functions to the Smallest x Values

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    An approach which unifies the Double Logarithmic Approximation at small x and the leading order DGLAP evolution of fragmentation functions at large x is presented. This approach reproduces exactly the Modified Leading Logarithm Approximation, but is more complete due to the degrees of freedom given to the quark sector and the inclusion of the fixed order terms. We find that data from the largest x values to the peak region can be better fitted than with other approaches.Comment: 10 pages, 3 figure

    Determination of fragmentation functions and their uncertainties from e+ + e- -> h + X data

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    Fragmentation functions are determined for pions, kaons, and nucleons by a global analysis of charged-hadron production data in electron-positron annihilation. The optimum functions are obtained in both leading order (LO) and next-to-leading order (NLO) of alpha_s. It is important that uncertainties of the fragmentation functions are estimated in this work by the Hessian method. We found that the uncertainties are large at small Q^2 and that they are generally reduced in the NLO in comparison with the LO ones. We supply a code for calculating the fragmentation functions and their uncertainties for the pions, kaons, and nucleons at given z and Q^2.Comment: 4 pages, LaTeX, 5 eps files, to be published in AIP proceedings of the 17th International Spin Physics Symposium (SPIN2006), Oct. 2-7, 2006, Kyoto, Japa

    Low-mass lepton pair production at large transverse momentum

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    We study the transverse momentum distribution of low-mass lepton pairs produced in hadronic scattering, using the perturbative QCD factorization approach. We argue that the distribution at large transverse momentum, QT≫QQ_T \gg Q, with the pair's invariant mass QQ as low as Q∼ΛQCDQ \sim \Lambda_{\mathrm{QCD}}, can be systematically factorized into universal parton-to-lepton pair fragmentation functions, parton distributions, and perturbatively calculable partonic hard parts evaluated at a short distance scale ∼O(1/QT)\sim {\cal O}(1/Q_T). We introduce a model for the input lepton pair fragmentation functions at a scale μ0∼1\mu_0\sim 1 GeV, which are then evolved perturbatively to scales relevant at RHIC. Using the evolved fragmentation functions, we calculate the transverse momentum distributions in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions at RHIC. We also discuss the sensitivity of the transverse momentum distribution of low-mass lepton pairs to the gluon distribution.Comment: 16 pages, 11 figures, revised version to appear in Phys. Rev.

    Photon - Jet Correlations and Constraints on Fragmentation Functions

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    We study the production of a large-pT photon in association with a jet in proton-proton collisions. We examine the sensitivity of the jet rapidity distribution to the gluon distribution function in the proton. We then assess the sensitivity of various photon + jet correlation observables to the photon fragmentation functions. We argue that RHIC data on photon-jet correlations can be used to constrain the photon fragmentation functions in a region which was barely accessible in LEP experiments.Comment: 23 pages, 9 figure

    A Next-to-Leading-Order Study of Dihadron Production

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    The production of pairs of hadrons in hadronic collisions is studied using a next-to-leading-order Monte Carlo program based on the phase space slicing technique. Up-to-date fragmentation functions based on fits to LEP data are employed, together with several versions of current parton distribution functions. Good agreement is found with data for the dihadron mass distribution. A comparison is also made with data for the dihadron angular distribution. The scale dependence of the predictions and the dependence on the choices made for the fragmentation and parton distribution functions are also presented. The good agreement between theory and experiment is contrasted to the case for single π0\pi^0 production where significant deviations between theory and experiment have been observed.Comment: 22 pages, 15 figures; 3 references added, one figure modified for clarit

    Identification of K 99 and 987 P attaching antigens of Escherichia coli in the pig in France

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    Les auteurs font état de l’identification en France des antigènes d’attachement K 99 et 987 P, à partir de souches d ’Escherichia coli responsables de diarrhée du porcelet nouveau-né. Ils discutent à ce propos des difficultés du diagnostic, des enquêtes épidémiologiques et de l’intérêt de l’incorporation de ces nouvelles valences dans les vaccins.Identification of K 99 and 987 P attaching antigens of ESCHERICHIA COLI IN THE PIG IN FRANCE The authors relate the detection of K 99 and 987 P pilus antigens on Escherichia coli enteropathogens for piglets in France. They dis cuss about the difficulty of the diagnostic and the prevalence of these pilus antigens and the interest of their incorporation in the vaccines
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