17,028 research outputs found
Could we learn more about HERA high anomaly from LEP200 and TEVATRON? R-parity violation scenario
The excess of high events at HERA reported in the early 1997 by H1 and
ZEUS collaborations has become the subject of extensive studies in the
framework of several models related to new physics. Here we concentrate on the
most promising, from our point of view, model describing HERA anomaly. We
update our previous analysis and take into account new HERA statistics of the
1997 year. HERA events are considered within the R-parity broken SUSY model for
a specific scenario with several non-zero couplings. R-parity broken SUSY with
several non-zero couplings could explain both high and observed at HERA. The consequence of such a particular scenario is the
excess of high di- or tri-jet events at HERA. The relation of this
scenario for LEP and TEVATRON colliders is considered. This study shows that if
a squark resonance does take place at HERA, supersymmetry with broken R-parity
can be revealed at either LEP200 or TEVATRON in the near future.Comment: 15 pages, LaTeX file with 9 eps figure
-pair Production in the Littlest Higgs Model with T parity in next-to-leading order QCD at LHC
In the framework of the littlest Higgs model with parity, we study the
-pair production at the CERN Large Hadron Collider up to the QCD
next-to-leading order (NLO). The kinematic distributions of final decay
products and the theoretical dependence of the cross section on the
factorization/renormalization scale are analyzed. We adopt the PROSPINO scheme
in the QCD NLO calculations to avoid double counting and keep the convergence
of the perturbative QCD description. Our numerical results show that the QCD
NLO corrections significantly reduce the scale uncertainty, and enhance the
leading order integrated cross section with a -factor in the range of
() with the symmetry breaking scale varying from
() to () at the LHC.
We find that it is possible to select the signal events of the -pair
production from the
background with high ratio of signature over background by taking proper lower
limits on transverse momenta, invariant mass of the final charged leptons and
the missing transverse momentum.Comment: 34 pages, 14 figures, 4 table
Minimal Supersymmetric Standard Model within CompHEP software package
The Minimal Supersymmetric Standard Model is presented as a model for the
CompHEP software package as a set of files containing the complete Lagrangian
of the MSSM, particle contents and parameters. All resources of CompHEP with a
user-friendly interface are now available for the phenomenological study of the
MSSM. Various special features of the model are discussed.Comment: 11 pages, LaTeX, submitted to Comp. Phys. Communicatio
W+2jets production at Tevatron -- VECBOS and CompHEP comparison
Results of calculation of all subprocesses in proton-antiproton collisions
which contribute to the W+2jets final state are presented at Tevatron energy.
The calculation has been carried out by means of the CompHEP software package.
A detail comparison with VECBOS generator results for cross sections and
various distributions shows an agreement at the level of Monte-Carlo accuracy.
Therefore the additional independent check of VECBOS generator has been done.
In complement to the VECBOS generator a new generator based on CompHEP allows
to study individual subprocesses like or . The last
point is important, for instance, for study part of the background
for single top or Standard Model Higgs signal at Tevatron.Comment: 8 pages including 4 figures as a gzipped postscript fil
Single top quarks at the Fermilab Tevatron
We present a calculation of the single top quark cross section for
proton-antiproton interactions with sqrt(s) = 1.8 TeV at the Fermilab Tevatron
collider. We examine the effects of top mass, parton distribution functions,
QCD scale, and collision energy, on each of the component production
mechanisms, and study the kinematic distributions for standard model
electroweak production. At the upgraded Tevatron with sqrt(s) = 2.0 TeV and
high luminosity, it will be possible to test the nature of the Wtb coupling
using single top production. We estimate the sensitivity to measure the single
top cross section, and thus to directly measure V_tb and the top quark partial
width. We show what happens to the V_tb measurement when an anomalous (V+A)
component is added to the Wtb coupling, and how the top quark polarization
affects the kinematic distributions.Comment: 31 pages including 11 figure
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