5,276 research outputs found
Top Pair Production Cross-Section Measurement in the All-Hadronic Channel at CDF and Dzero
Measurements of the ttbar production cross-section at \sqrt{s} = 1.96TeV in
proton-antiproton collisions were performed by the CDF and Dzero collaborations
using ttbar final states where both W's decay hadronically. Each experiment
uses luminosity of about 160pb^-1 of data collected during Run II of the
Fermilab Tevatron collider. Beside kinematical observables both experiments
take advantage of identifying b-jets based on lifetime tagging. While CDF
counts the number of b-tags over background after a cut based analysis, Dzero
counts the excess of events after a neural network based kinematical selection
and requiring a b-tagged jet.
CDF obtains \sigma_{ttbar}=7.7^{+3.4}_{-3.3}{stat}^{+4.7}_{-3.8}{syst}+-0.5{lumi}.Comment: 4 pages, 2 figures, Proceedings to DPF2004, Riverside, C
Distributed Computing Concepts in D0
The D0 experiment faces many challenges enabling access to large datasets for
physicists on four continents. The new concepts for distributed large scale
computing implemented in D0 aim for an optimal use of the available computing
resources while minimising the person-power needed for operation. The real live
test of these concepts is of special interest for the LHC Computing GRID, LCG,
which follows a similar strategy.Comment: 3 pages, 3 figures, LaTeX, epj style (included), Proceedings of the
International Europhysics Conference on High Energy Physics EPS 2003 (July
17-23, 2003), Aachen, German
Single and Double Top Quark Production at the Tevatron
The CDF and D0 experiments have measured single and double top quark
production in ppbar collisions at the Tevatron at a centre-of-mass energy of
1.96TeV. The applied methods are used to constrain properties of the top quark
and to search for new physics. Several methods of signal to background
separation and of the estimation of the background contributions are discussed.
Experimental results using an integraged luminosity up to 5.3fb^-1 are
presented.Comment: 8 pages with figures, Proceedings of Les Rencontres de Physique de la
Vall\'ee d'Aoste (La Thuile 2010), v2 with updated reference
Hadronic event structure, power corrections and the strong coupling at LEP
Infrared and collinear events shapes are suited to directly probe properties
of hard QCD. They are traditionally used to measure the strong coupling and to
test the gauge structure of QCD. Perturbative predictions exist in several
variations all of which depend on the renormalisation scheme leading to large
theoretical uncertainties in the determination of . To overcome this
dominating error more and more schemes for setting the renormalisation scale
are investigated. The application of RGI perturbation theory shows an
incredible small spread of indicating a reduced uncertainty and
allows a measurement of the -function directly from mean values.Comment: 5 pages, uses moriond.sty (included). Contribution to "XXXVIIth
Rencontres de Moriond, QCD and hadronic interactions", Les Arcs, France,
March 2002. See http://www.delphi.uni-wuppertal.de/qcd/Talks.html#Moriond200
Non-perturbative QCD Effects and the Top Mass at the Tevatron
The modelling of non-perturbative effects is an important part of modern
collider physics simulations. In hadron collisions there is some indication
that the modelling of the interactions of the beam remnants, the underlying
event, may require non-trivial colour reconnection effects to be present. We
recently introduced a universally applicable toy model of such reconnections,
based on hadronising strings. This model, which has one free parameter, has
been implemented in the Pythia event generator. We then considered several
parameter sets (`tunes'), constrained by fits to Tevatron minimum-bias data,
and determined the sensitivity of a simplified top mass analysis to these
effects, in exclusive semi-leptonic top events at the Tevatron. A first attempt
at isolating the genuine non-perturbative effects gave an estimate of order
+-0.5GeV from non-perturbative uncertainties. The results presented here are an
update to the original study and include recent bug fixes of Pythia that
influenced the tunings investigated.Comment: 8 pages, 5 figures, Submitted to the Proceedings of Top2008, 18-24
May 2008, La Biodola, Isola d'Elba, Ital
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