5,054 research outputs found
A new jet algorithm based on the k-means clustering for the reconstruction of heavy states from jets
A jet algorithm based on the k-means clustering procedure is proposed which
can be used for the invariant-mass reconstruction of heavy states decaying to
hadronic jets. The proposed algorithm was tested by reconstructing E+ E- to
ttbar to 6 jets and E+ E- to W+W- to 4 jets processes at \sqrt{s}=500 GeV using
a Monte Carlo simulation. It was shown that the algorithm has a reconstruction
efficiency similar to traditional jet-finding algorithms, and leads to 25% and
40% reduction of reconstruction width for top quarks and W bosons,
respectively, compared to the kT (Durham) algorithm. In addition, it is
expected that the peak positions measured with the new algorithm have smaller
systematical uncertainty.Comment: 11 pages, 3 eps figures (Eur. Phys. J. C, in press
Combined HERA Deep Inelastic Scattering Data and NLO QCD Fits
Previously published data on inclusive neutral and charged current e+p and
e-p deep inelastic scattering from HERA have been combined. The new,
model-independent method of combining the measured cross sections takes full
account of correlated systematics in a coherent way, leading to significantly
reduced uncertainties in the combined measurement across the (x, Q^2) plane.
The combined cross section data have been used as the sole input for a new
next-to-leading order QCD fit to extract the parton distribution functions
(PDFs) of the proton. The PDFs extracted have greatly reduced experimental
uncertainties, compared to separate QCD analyses on data from H1 and ZEUS.
Model uncertainties, including those arising from the parameterisation
dependence, have also been carefully considered. The resulting HERA PDFs have
impressive precision.Comment: 11 pages, 6 figures, prepared for the proceedings of the Ringberg
Workshop on "New Trends in HERA Physics 2008", Ringberg Castle, Tegernsee,
Oct 5-10, 200
Heavy Quark Production at HERA
Heavy flavour production is one of the key components of the HERA II physics
programme. While most of the results presented use leptons or the
reconstruction of charmed mesons to identify heavy flavour production, both the
H1 and ZEUS experiments now have working microvertex detectors that are being
used more and more. In this talk I will summarise a selection of the recent
results obtained by the two collaborations.Comment: 10 pages, 18 figures, to appear in the Proceedings of the 8th
International Conference on Hyperons, Charm and Beauty Hadrons (BEACH2008),
22-28 June 2008, University of South Carolina, Columbi
Jets in Deep Inelastic Scattering and High Energy Photoproduction at HERA
Recent results on jet production in neutral current deep inelastic scattering
and high energy photoproduction at the HERA electron-proton-collider are
briefly reviewed. The results are compared to QCD expectations in NLO and
determinations using these data are summarized.Comment: 12 pages, 10 figures, talk given at the 9th Adriatic Meeting
"Particle Physics and the Universe" in Dubrovnik/Croatia, 4.-24.9.200
HepSim: a repository with predictions for high-energy physics experiments
A file repository for calculations of cross sections and kinematic
distributions using Monte Carlo generators for high-energy collisions is
discussed. The repository is used to facilitate effective preservation and
archiving of data from theoretical calculations, as well as for comparisons
with experimental data. The HepSim data library is publicly accessible and
includes a number of Monte Carlo event samples with Standard Model predictions
for current and future experiments. The HepSim project includes a software
package to automate the process of downloading and viewing online Monte Carlo
event samples. A data streaming over a network for end-user analysis is
discussed.Comment: 12 pages, 2 figure
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