1,000 research outputs found
Measurement of triple differential photon plus jet cross section by D0
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
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- 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
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
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
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, , with the pair's invariant mass as low as , 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 . We introduce a model for the input lepton pair
fragmentation functions at a scale 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
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
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 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
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
- …