5,290 research outputs found
Optimized Neural Networks to Search for Higgs Boson Production at the Tevatron
An optimal choice of proper kinematical variables is one of the main steps in
using neural networks (NN) in high energy physics. Our method of the variable
selection is based on the analysis of a structure of Feynman diagrams
(singularities and spin correlations) contributing to the signal and background
processes. An application of this method to the Higgs boson search at the
Tevatron leads to an improvement in the NN efficiency by a factor of 1.5-2 in
comparison to previous NN studies.Comment: 4 pages, 4 figures, partially presented in proceedings of ACAT'02
conferenc
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
Light and Intermediate Higgs boson search at Tevatron Energies
We study the Higgs boson search possibility at the TEVATRON energies. The
detailed analysis of the 4-fermion final state reactions is presented. Among
the complete set of Feynman diagrams the main contribution to the final states
comes from the Higgs signal WH and ZH, from the backgrounds WZ, ZZ and gluonic
background Wbb, Zbb with subssiquent decays of W, Z bosons. It is shown that
the important contribution to the background is connected with single top quark
production subreactions qq-bar --> tb-bar or t-bar b with the top decay to Wb.
As a result of various distributions for Higgs signal and backgrounds a number
of optimum cuts has been found. The finaleffective -- pair mass
distribution allows to extract the signal from Higgs with mass up to about 100
GeV at 2 TeV C.M. energy and up to about 120 GeV at 4 TeV C.M. energy for the
integrated luminosity 1000 inverse pb.Comment: 18 pages including 8 figures as 9 gzipped and uuencoded postscript
file
Higgs boson production under the resonance threshold at LEP II
We consider the possibility of Higgs boson detection at LEP II under the
resonance threshold () in the framework of complete tree
level approach to the calculation of the amplitude, simulating b-quark fragmentation to hadrons and taking into
account typical detector properties. At the energy below the threshold
175 GeV Higgs boson production under the threshold is
practically background free.Comment: 19 pages, including 1 figure in LaTeX, 8 postscript figure
LCG MCDB -- a Knowledgebase of Monte Carlo Simulated Events
In this paper we report on LCG Monte Carlo Data Base (MCDB) and software
which has been developed to operate MCDB. The main purpose of the LCG MCDB
project is to provide a storage and documentation system for sophisticated
event samples simulated for the LHC collaborations by experts. In many cases,
the modern Monte Carlo simulation of physical processes requires expert
knowledge in Monte Carlo generators or significant amount of CPU time to
produce the events. MCDB is a knowledgebase mainly dedicated to accumulate
simulated events of this type. The main motivation behind LCG MCDB is to make
the sophisticated MC event samples available for various physical groups. All
the data from MCDB is accessible in several convenient ways. LCG MCDB is being
developed within the CERN LCG Application Area Simulation project
W + 2 jets 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 independent check of VECBOS generator has been done. In addition to the VECBOS generator a new generator based on CompHEP allows to study individual subprocesses like Wb\bar{b} or Wc\bar{c}. The last point is important, for instance, for study Wb\bar{b} part of the background for single top or Standard Model Higgs signal at Tevatron
CompHEP 4.4 - Automatic Computations from Lagrangians to Events
We present a new version of the CompHEP program (version 4.4). We describe
shortly new issues implemented in this version, namely, simplification of quark
flavor combinatorics for the evaluation of hadronic processes, Les Houches
Accord based CompHEP-PYTHIA interface, processing the color configurations of
events, implementation of MSSM, symbolical and numerical batch modes, etc. We
discuss how the CompHEP program is used for preparing event generators for
various physical processes. We mention a few concrete physics examples for
CompHEP based generators prepared for the LHC and Tevatron.Comment: The paper has been presented on IX International Workshop on Advanced
Computing and Analysis Techniques in Physics Research December 1-5, 2003.
KEK, Japan. 10 pages, 2 figure
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